[PATCH v2 00/14] util: sync error_report & qemu_log output more closely

[PATCH v2 00/14] util: sync error_report & qemu_log output more closely

[Daniel P. Berrangé]

This series is a tangent that came out of discussion in

   https://lists.nongnu.org/archive/html/qemu-devel/2025-08/msg00903.html

In thinking about adding thread info to error_report, I
came to realize we should likely make qemu_log behave
consistently with error_report & friends. We already
honour '-msg timestamp=on', but don't honour 'guest-name=on'
and also don't include the binary name.

As an example of the current state, consider mixing error and
log output today:

- Default context:

  # qemu-system-x86_64 -object tls-creds-x509,id=t0,dir=fish \
                       -d 'trace:qcrypto*'
  qcrypto_tls_creds_x509_load TLS creds x509 load creds=0x55ac6d97f700 dir=fish
  qcrypto_tls_creds_get_path TLS creds path creds=0x55ac6d97f700 filename=ca-cert.pem path=<none>
  qemu-system-x86_64: Unable to access credentials fish/ca-cert.pem: No such file or directory

- Full context:

  # qemu-system-x86_64 -object tls-creds-x509,id=t0,dir=fish \
                       -d 'trace:qcrypto*' \
                       -msg guest-name=on,timestamp=on \
                       -name "fish food"
  2025-08-19T20:14:16.791413Z qcrypto_tls_creds_x509_load TLS creds x509 load creds=0x55e9a3458d10 dir=fish
  2025-08-19T20:14:16.791429Z qcrypto_tls_creds_get_path TLS creds path creds=0x55e9a3458d10 filename=ca-cert.pem path=<none>
  2025-08-19T20:14:16.791433Z fish food qemu-system-x86_64: Unable to access credentials fish/ca-cert.pem: No such file or directory

And after this series is complete:

- Default context:

  # qemu-system-x86_64 -object tls-creds-x509,id=t0,dir=fish \
                      -d 'trace:qcrypto*'
  qemu-system-x86_64(1184284:main): qcrypto_tls_creds_x509_load TLS creds x509 load creds=0x55a24ad5cb30 dir=fish
  qemu-system-x86_64(1184284:main): qcrypto_tls_creds_get_path TLS creds path creds=0x55a24ad5cb30 filename=ca-cert.pem path=<none>
  qemu-system-x86_64(1184284:main): Unable to access credentials fish/ca-cert.pem: No such file or directory

- Full context:

  # qemu-system-x86_64 -object tls-creds-x509,id=t0,dir=fish \
                      -d 'trace:qcrypto*' \
                      -msg guest-name=on,timestamp=on \
                      -name "fish food"
  2025-08-19T20:12:50.211823Z [fish food] qemu-system-x86_64(1168876:main): qcrypto_tls_creds_x509_load TLS creds x509 load creds=0x5582183d8760 dir=fish
  2025-08-19T20:12:50.211842Z [fish food] qemu-system-x86_64(1168876:main): qcrypto_tls_creds_get_path TLS creds path creds=0x5582183d8760 filename=ca-cert.pem path=<none>
  2025-08-19T20:12:50.211846Z [fish food] qemu-system-x86_64(1168876:main): Unable to access credentials fish/ca-cert.pem: No such file or directory

The main things to note:

 * error_report/warn_report/qemu_log share the same
   output format and -msg applies to both

 * -msg debug-threads=on is now unconditionally enabled
   and thus the param is deprecated & ignored

 * Thread ID and name are unconditionally enabled

 * Guest name is surrounded in [...] brackets

 * The default output lines are typically 15 chars
   wider given that we always include the thread
   ID + name now

 * This takes the liberty of assigning the new file
   to the existing error-report.c maintainer (Markus)
   Since splitting it off into message.c instead of
   putting it all in error-report.c felt slightly
   nicer.

One thing I didn't tackle is making the location
info get reported for qemu_log. This is used to
give context for error messages when parsing some
CLI args, and could be interesting for log messages
associated with those same CLI args.

Changes in v2:

 - Re-use existing qemu_get_thread_id rather than
   re-inventing it as qemu_thread_get_id.
 - Expose qemu_thread_set_name and use it from all
   locations needing to set thread names
 - Fix qemu_log() to skip context prefix when
   emitting a log message in fragments across
   multiple calls
 - Skip allocating memory for empty context messages
 - Fix leak in win32 impl of qemu_thread_get_name
 - Use g_strlcpy where possible

Daniel P. Berrangé (14):
  include: define constant for early constructor priority
  monitor: initialize global data from a constructor
  system: unconditionally enable thread naming
  util: expose qemu_thread_set_name
  audio: make jackaudio use qemu_thread_set_name
  util: set the name for the 'main' thread
  util: add API to fetch the current thread name
  log: avoid prefix on split qemu_log calls
  util: introduce common helper for error-report & log code
  util: convert error-report & log to message API for timestamp
  util: add support for formatting a workload name in messages
  util: add support for formatting a program name in messages
  util: add support for formatting thread info in messages
  util: add brackets around guest name in message context

 MAINTAINERS                          |  2 +
 audio/jackaudio.c                    | 28 ++++++++--
 docs/about/deprecated.rst            |  7 +++
 include/qemu/compiler.h              |  8 +++
 include/qemu/error-report.h          |  4 --
 include/qemu/message.h               | 52 ++++++++++++++++++
 include/qemu/thread.h                |  3 +-
 meson.build                          | 21 +++++++
 monitor/monitor.c                    | 14 +++--
 storage-daemon/qemu-storage-daemon.c |  6 ++
 system/vl.c                          | 30 +++++++---
 tests/qemu-iotests/041               |  2 +-
 tests/qemu-iotests/common.filter     |  2 +-
 tests/unit/test-error-report.c       |  6 +-
 util/error-report.c                  | 29 ++--------
 util/log.c                           | 28 ++++++----
 util/meson.build                     |  1 +
 util/message.c                       | 73 +++++++++++++++++++++++++
 util/qemu-thread-posix.c             | 76 +++++++++++++++++---------
 util/qemu-thread-win32.c             | 82 +++++++++++++++++++---------
 20 files changed, 357 insertions(+), 117 deletions(-)
 create mode 100644 include/qemu/message.h
 create mode 100644 util/message.c

-- 
2.50.1

[PATCH v2 01/14] include: define constant for early constructor priority

[Daniel P. Berrangé]

Functions marked with __attribute__((__constructor__)) will be
invoked in linker order. In theory this is well defined, but
in practice, it is hard to determine what this order will be
with the layers of indirection through meson, ninja and the
static libraries QEMU builds.

Notably, the order currently appears different between Linux
and Windows (as tested with Wine on Linux). This can cause
problems when certain QEMU constructors have a dependancy on
other QEMU constructors.

To address this define a QEMU_CONSTRUCTOR_EARLY constant which
provides a priority value that will run before other default
constructors. This is to be used for QEMU constructors that
are themselves self-contained, but may be relied upon by other
constructors.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 include/qemu/compiler.h | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/include/qemu/compiler.h b/include/qemu/compiler.h
index 1c2b673c05..4c49f52eb0 100644
--- a/include/qemu/compiler.h
+++ b/include/qemu/compiler.h
@@ -194,6 +194,14 @@
 # define QEMU_USED
 #endif
 
+/*
+ * A priority for __attribute__((constructor(...))) that
+ * will run earlier than the default constructors. Must
+ * only be used for functions that have no dependency
+ * on global initialization of other QEMU subsystems.
+ */
+#define QEMU_CONSTRUCTOR_EARLY 101
+
 /*
  * Disable -ftrivial-auto-var-init on a local variable.
  *
-- 
2.50.1

[PATCH v2 02/14] monitor: initialize global data from a constructor

[Daniel P. Berrangé]

Some monitor functions, most notably, monitor_cur() rely on global
data being initialized by 'monitor_init_globals()'. The latter is
called relatively late in startup. If code triggers error_report()
before monitor_init_globals() is called, QEMU will abort when
accessing the uninitialized monitor mutex.

The critical monitor global data must be initialized from a
constructor function, to improve the guarantee that it is done
before any possible calls to monitor_cur(). Not only that, but
the constructor must be marked to run before the default
constructor in case any of them trigger error reporting.

Note in particular that the RCU constructor will spawn a background
thread so we might even have non-constructor QEMU code running
concurrently with other constructors.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 monitor/monitor.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/monitor/monitor.c b/monitor/monitor.c
index c5a5d30877..da54e1b1ce 100644
--- a/monitor/monitor.c
+++ b/monitor/monitor.c
@@ -704,18 +704,22 @@ void monitor_cleanup(void)
     }
 }
 
-static void monitor_qapi_event_init(void)
+/*
+ * Initialize static vars that have no deps on external
+ * module initialization, and are required for external
+ * functions to call things like monitor_cur()
+ */
+static void __attribute__((__constructor__(QEMU_CONSTRUCTOR_EARLY)))
+monitor_init_static(void)
 {
+    qemu_mutex_init(&monitor_lock);
+    coroutine_mon = g_hash_table_new(NULL, NULL);
     monitor_qapi_event_state = g_hash_table_new(qapi_event_throttle_hash,
                                                 qapi_event_throttle_equal);
 }
 
 void monitor_init_globals(void)
 {
-    monitor_qapi_event_init();
-    qemu_mutex_init(&monitor_lock);
-    coroutine_mon = g_hash_table_new(NULL, NULL);
-
     /*
      * The dispatcher BH must run in the main loop thread, since we
      * have commands assuming that context.  It would be nice to get
-- 
2.50.1

[PATCH v2 03/14] system: unconditionally enable thread naming

[Daniel P. Berrangé]

When thread naming was introduced years ago, it was disabled by
default and put behind a command line flag:

  commit 8f480de0c91a18d550721f8d9af969ebfbda0793
  Author: Dr. David Alan Gilbert <dgilbert@redhat.com>
  Date:   Thu Jan 30 10:20:31 2014 +0000

    Add 'debug-threads' suboption to --name

This was done based on a concern that something might depend
on the historical thread naming. Thread names, however, were
never promised to be part of QEMU's public API. The defaults
will vary across platforms, so no assumptions should ever be
made about naming.

An opt-in behaviour is also unfortunately incompatible with
RCU which creates its thread from an constructor function
which is run before command line args are parsed. Thus the
RCU thread lacks any name.

libvirt has unconditionally enabled debug-threads=yes on all
VMs it creates for 10 years. Interestingly this DID expose a
bug in libvirt, as it parsed /proc/$PID/stat and could not
cope with a space in the thread name. This was a latent
pre-existing bug in libvirt though, and not a part of QEMU's
API.

Having thread names always available, will allow thread names
to be included in error reports and log messags QEMU prints
by default, which will improve ability to triage QEMU bugs.

Reviewed-by: Dr. David Alan Gilbert <dave@treblig.org>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 docs/about/deprecated.rst |  7 +++++++
 include/qemu/thread.h     |  1 -
 system/vl.c               | 11 ++++++-----
 util/qemu-thread-posix.c  | 18 +-----------------
 util/qemu-thread-win32.c  | 27 ++++++---------------------
 5 files changed, 20 insertions(+), 44 deletions(-)

diff --git a/docs/about/deprecated.rst b/docs/about/deprecated.rst
index d50645a071..bd6f865558 100644
--- a/docs/about/deprecated.rst
+++ b/docs/about/deprecated.rst
@@ -81,6 +81,13 @@ kernel since 2001. None of the board types QEMU supports need
 ``param_struct`` support, so this option has been deprecated and will
 be removed in a future QEMU version.
 
+``debug-threads`` option for ``-name``
+''''''''''''''''''''''''''''''''''''''
+
+Thread ``debug-threads`` option for the ``-name`` argument is now
+ignored. Thread naming is unconditionally enabled for all platforms
+where it is supported.
+
 User-mode emulator command line arguments
 -----------------------------------------
 
diff --git a/include/qemu/thread.h b/include/qemu/thread.h
index f0302ed01f..3a286bb3ef 100644
--- a/include/qemu/thread.h
+++ b/include/qemu/thread.h
@@ -215,7 +215,6 @@ void *qemu_thread_join(QemuThread *thread);
 void qemu_thread_get_self(QemuThread *thread);
 bool qemu_thread_is_self(QemuThread *thread);
 G_NORETURN void qemu_thread_exit(void *retval);
-void qemu_thread_naming(bool enable);
 
 struct Notifier;
 /**
diff --git a/system/vl.c b/system/vl.c
index 3b7057e6c6..a64fd90d4a 100644
--- a/system/vl.c
+++ b/system/vl.c
@@ -403,9 +403,7 @@ static QemuOptsList qemu_name_opts = {
         }, {
             .name = "debug-threads",
             .type = QEMU_OPT_BOOL,
-            .help = "When enabled, name the individual threads; defaults off.\n"
-                    "NOTE: The thread names are for debugging and not a\n"
-                    "stable API.",
+            .help = "DEPRECATED: thread names are always set where supported",
         },
         { /* End of list */ }
     },
@@ -554,9 +552,12 @@ static int parse_name(void *opaque, QemuOpts *opts, Error **errp)
 {
     const char *proc_name;
 
-    if (qemu_opt_get(opts, "debug-threads")) {
-        qemu_thread_naming(qemu_opt_get_bool(opts, "debug-threads", false));
+    if (qemu_opt_get(opts, "debug-threads") &&
+        !qemu_opt_get_bool(opts, "debug-threads", false)) {
+        fprintf(stderr, "Ignoring deprecated 'debug-threads=no' option, " \
+                "thread naming is unconditionally enabled\n");
     }
+
     qemu_name = qemu_opt_get(opts, "guest");
 
     proc_name = qemu_opt_get(opts, "process");
diff --git a/util/qemu-thread-posix.c b/util/qemu-thread-posix.c
index ba725444ba..7c985b5d38 100644
--- a/util/qemu-thread-posix.c
+++ b/util/qemu-thread-posix.c
@@ -22,22 +22,6 @@
 #include <pthread_np.h>
 #endif
 
-static bool name_threads;
-
-void qemu_thread_naming(bool enable)
-{
-    name_threads = enable;
-
-#if !defined CONFIG_PTHREAD_SETNAME_NP_W_TID && \
-    !defined CONFIG_PTHREAD_SETNAME_NP_WO_TID && \
-    !defined CONFIG_PTHREAD_SET_NAME_NP
-    /* This is a debugging option, not fatal */
-    if (enable) {
-        fprintf(stderr, "qemu: thread naming not supported on this host\n");
-    }
-#endif
-}
-
 static void error_exit(int err, const char *msg)
 {
     fprintf(stderr, "qemu: %s: %s\n", msg, strerror(err));
@@ -361,7 +345,7 @@ static void *qemu_thread_start(void *args)
     /* Attempt to set the threads name; note that this is for debug, so
      * we're not going to fail if we can't set it.
      */
-    if (name_threads && qemu_thread_args->name) {
+    if (qemu_thread_args->name) {
 # if defined(CONFIG_PTHREAD_SETNAME_NP_W_TID)
         pthread_setname_np(pthread_self(), qemu_thread_args->name);
 # elif defined(CONFIG_PTHREAD_SETNAME_NP_WO_TID)
diff --git a/util/qemu-thread-win32.c b/util/qemu-thread-win32.c
index ca2e0b512e..9595a5b090 100644
--- a/util/qemu-thread-win32.c
+++ b/util/qemu-thread-win32.c
@@ -17,8 +17,6 @@
 #include "qemu-thread-common.h"
 #include <process.h>
 
-static bool name_threads;
-
 typedef HRESULT (WINAPI *pSetThreadDescription) (HANDLE hThread,
                                                  PCWSTR lpThreadDescription);
 static pSetThreadDescription SetThreadDescriptionFunc;
@@ -44,16 +42,6 @@ static bool load_set_thread_description(void)
     return !!SetThreadDescriptionFunc;
 }
 
-void qemu_thread_naming(bool enable)
-{
-    name_threads = enable;
-
-    if (enable && !load_set_thread_description()) {
-        fprintf(stderr, "qemu: thread naming not supported on this host\n");
-        name_threads = false;
-    }
-}
-
 static void error_exit(int err, const char *msg)
 {
     char *pstr;
@@ -328,23 +316,20 @@ void *qemu_thread_join(QemuThread *thread)
     return ret;
 }
 
-static bool set_thread_description(HANDLE h, const char *name)
+static void set_thread_description(HANDLE h, const char *name)
 {
-    HRESULT hr;
     g_autofree wchar_t *namew = NULL;
 
     if (!load_set_thread_description()) {
-        return false;
+        return;
     }
 
     namew = g_utf8_to_utf16(name, -1, NULL, NULL, NULL);
     if (!namew) {
-        return false;
+        return;
     }
 
-    hr = SetThreadDescriptionFunc(h, namew);
-
-    return SUCCEEDED(hr);
+    SetThreadDescriptionFunc(h, namew);
 }
 
 void qemu_thread_create(QemuThread *thread, const char *name,
@@ -370,8 +355,8 @@ void qemu_thread_create(QemuThread *thread, const char *name,
     if (!hThread) {
         error_exit(GetLastError(), __func__);
     }
-    if (name_threads && name && !set_thread_description(hThread, name)) {
-        fprintf(stderr, "qemu: failed to set thread description: %s\n", name);
+    if (name) {
+        set_thread_description(hThread, name);
     }
     CloseHandle(hThread);
 
-- 
2.50.1

[PATCH v2 04/14] util: expose qemu_thread_set_name

[Daniel P. Berrangé]

The ability to set the thread name needs to be used in a number
of places, so expose the current impls as public methods.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 include/qemu/thread.h    |  1 +
 util/qemu-thread-posix.c | 30 ++++++++++++++++++------------
 util/qemu-thread-win32.c |  6 +++---
 3 files changed, 22 insertions(+), 15 deletions(-)

diff --git a/include/qemu/thread.h b/include/qemu/thread.h
index 3a286bb3ef..27b888ab0a 100644
--- a/include/qemu/thread.h
+++ b/include/qemu/thread.h
@@ -215,6 +215,7 @@ void *qemu_thread_join(QemuThread *thread);
 void qemu_thread_get_self(QemuThread *thread);
 bool qemu_thread_is_self(QemuThread *thread);
 G_NORETURN void qemu_thread_exit(void *retval);
+void qemu_thread_set_name(const char *name);
 
 struct Notifier;
 /**
diff --git a/util/qemu-thread-posix.c b/util/qemu-thread-posix.c
index 7c985b5d38..ddaa1de4dd 100644
--- a/util/qemu-thread-posix.c
+++ b/util/qemu-thread-posix.c
@@ -329,6 +329,21 @@ static void qemu_thread_atexit_notify(void *arg)
     notifier_list_notify(&thread_exit, NULL);
 }
 
+void qemu_thread_set_name(const char *name)
+{
+    /*
+     * Attempt to set the threads name; note that this is for debug, so
+     * we're not going to fail if we can't set it.
+     */
+# if defined(CONFIG_PTHREAD_SETNAME_NP_W_TID)
+    pthread_setname_np(pthread_self(), name);
+# elif defined(CONFIG_PTHREAD_SETNAME_NP_WO_TID)
+    pthread_setname_np(name);
+# elif defined(CONFIG_PTHREAD_SET_NAME_NP)
+    pthread_set_name_np(pthread_self(), name);
+# endif
+}
+
 typedef struct {
     void *(*start_routine)(void *);
     void *arg;
@@ -342,20 +357,11 @@ static void *qemu_thread_start(void *args)
     void *arg = qemu_thread_args->arg;
     void *r;
 
-    /* Attempt to set the threads name; note that this is for debug, so
-     * we're not going to fail if we can't set it.
-     */
     if (qemu_thread_args->name) {
-# if defined(CONFIG_PTHREAD_SETNAME_NP_W_TID)
-        pthread_setname_np(pthread_self(), qemu_thread_args->name);
-# elif defined(CONFIG_PTHREAD_SETNAME_NP_WO_TID)
-        pthread_setname_np(qemu_thread_args->name);
-# elif defined(CONFIG_PTHREAD_SET_NAME_NP)
-        pthread_set_name_np(pthread_self(), qemu_thread_args->name);
-# endif
+        qemu_thread_set_name(qemu_thread_args->name);
+        QEMU_TSAN_ANNOTATE_THREAD_NAME(qemu_thread_args->name);
+        g_free(qemu_thread_args->name);
     }
-    QEMU_TSAN_ANNOTATE_THREAD_NAME(qemu_thread_args->name);
-    g_free(qemu_thread_args->name);
     g_free(qemu_thread_args);
 
     /*
diff --git a/util/qemu-thread-win32.c b/util/qemu-thread-win32.c
index 9595a5b090..62eaa11026 100644
--- a/util/qemu-thread-win32.c
+++ b/util/qemu-thread-win32.c
@@ -316,7 +316,7 @@ void *qemu_thread_join(QemuThread *thread)
     return ret;
 }
 
-static void set_thread_description(HANDLE h, const char *name)
+void qemu_thread_set_name(const char *name)
 {
     g_autofree wchar_t *namew = NULL;
 
@@ -329,7 +329,7 @@ static void set_thread_description(HANDLE h, const char *name)
         return;
     }
 
-    SetThreadDescriptionFunc(h, namew);
+    SetThreadDescriptionFunc(GetCurrentThread(), namew);
 }
 
 void qemu_thread_create(QemuThread *thread, const char *name,
@@ -356,7 +356,7 @@ void qemu_thread_create(QemuThread *thread, const char *name,
         error_exit(GetLastError(), __func__);
     }
     if (name) {
-        set_thread_description(hThread, name);
+        qemu_thread_set_name(name);
     }
     CloseHandle(hThread);
 
-- 
2.50.1

[PATCH v2 05/14] audio: make jackaudio use qemu_thread_set_name

[Daniel P. Berrangé]

This has greater portability than directly call pthread_setname_np,
which is only 1 out of 3 possible functions for pthreads that can
set the name.

The new API requires a trampoline function, since it can only set
the name of the current thread.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 audio/jackaudio.c | 28 +++++++++++++++++++++++-----
 1 file changed, 23 insertions(+), 5 deletions(-)

diff --git a/audio/jackaudio.c b/audio/jackaudio.c
index 974a3caad3..48ffbf735f 100644
--- a/audio/jackaudio.c
+++ b/audio/jackaudio.c
@@ -629,18 +629,36 @@ static void qjack_enable_in(HWVoiceIn *hw, bool enable)
     ji->c.enabled = enable;
 }
 
-#if !defined(WIN32) && defined(CONFIG_PTHREAD_SETNAME_NP_W_TID)
+#if !defined(WIN32)
+struct QJackThreadData {
+    void *(*function)(void *);
+    void *arg;
+};
+
+static void *qjack_thread_trampoline(void *targ)
+{
+    struct QJackThreadData *data = targ;
+    void *(*function)(void *) = data->function;
+    void *arg = data->arg;
+
+    g_free(data);
+    qemu_thread_set_name("jack-client");
+
+    return function(arg);
+}
+
 static int qjack_thread_creator(jack_native_thread_t *thread,
     const pthread_attr_t *attr, void *(*function)(void *), void *arg)
 {
-    int ret = pthread_create(thread, attr, function, arg);
+    struct QJackThreadData *data = g_new0(struct QJackThreadData, 1);
+    data->function = function;
+    data->arg = arg;
+    int ret = pthread_create(thread, attr, qjack_thread_trampoline, data);
     if (ret != 0) {
+        g_free(data);
         return ret;
     }
 
-    /* set the name of the thread */
-    pthread_setname_np(*thread, "jack-client");
-
     return ret;
 }
 #endif
-- 
2.50.1

[PATCH v2 06/14] util: set the name for the 'main' thread

[Daniel P. Berrangé]

The default main thread name is undefined, so use a constructor to
explicitly set it to 'main'. This constructor is marked to run early
as the thread name is intended to be used in error reporting / logs
which may be triggered very early in QEMU execution.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 util/qemu-thread-posix.c | 6 ++++++
 util/qemu-thread-win32.c | 6 ++++++
 2 files changed, 12 insertions(+)

diff --git a/util/qemu-thread-posix.c b/util/qemu-thread-posix.c
index ddaa1de4dd..275445ed94 100644
--- a/util/qemu-thread-posix.c
+++ b/util/qemu-thread-posix.c
@@ -22,6 +22,12 @@
 #include <pthread_np.h>
 #endif
 
+static void __attribute__((__constructor__(QEMU_CONSTRUCTOR_EARLY)))
+qemu_thread_init(void)
+{
+    qemu_thread_set_name("main");
+}
+
 static void error_exit(int err, const char *msg)
 {
     fprintf(stderr, "qemu: %s: %s\n", msg, strerror(err));
diff --git a/util/qemu-thread-win32.c b/util/qemu-thread-win32.c
index 62eaa11026..7a734a7a09 100644
--- a/util/qemu-thread-win32.c
+++ b/util/qemu-thread-win32.c
@@ -22,6 +22,12 @@ typedef HRESULT (WINAPI *pSetThreadDescription) (HANDLE hThread,
 static pSetThreadDescription SetThreadDescriptionFunc;
 static HMODULE kernel32_module;
 
+static void __attribute__((__constructor__(QEMU_CONSTRUCTOR_EARLY)))
+qemu_thread_init(void)
+{
+    qemu_thread_set_name("main");
+}
+
 static bool load_set_thread_description(void)
 {
     static gsize _init_once = 0;
-- 
2.50.1

[PATCH v2 07/14] util: add API to fetch the current thread name

[Daniel P. Berrangé]

This will be used to include the thread name in error reports
in a later patch. It returns a const string stored in a thread
local to avoid memory allocation when it is called repeatedly
in a single thread. This makes the assumption that the thread
name is set at the very start of the thread, which is the case
when using qemu_thread_create.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 include/qemu/thread.h    |  1 +
 meson.build              | 21 +++++++++++++++++
 util/qemu-thread-posix.c | 28 ++++++++++++++++++++++-
 util/qemu-thread-win32.c | 49 ++++++++++++++++++++++++++++++++++++----
 4 files changed, 94 insertions(+), 5 deletions(-)

diff --git a/include/qemu/thread.h b/include/qemu/thread.h
index 27b888ab0a..98cc5c41ac 100644
--- a/include/qemu/thread.h
+++ b/include/qemu/thread.h
@@ -216,6 +216,7 @@ void qemu_thread_get_self(QemuThread *thread);
 bool qemu_thread_is_self(QemuThread *thread);
 G_NORETURN void qemu_thread_exit(void *retval);
 void qemu_thread_set_name(const char *name);
+const char *qemu_thread_get_name(void);
 
 struct Notifier;
 /**
diff --git a/meson.build b/meson.build
index 0d42de61ae..5d610224fa 100644
--- a/meson.build
+++ b/meson.build
@@ -2920,6 +2920,27 @@ config_host_data.set('CONFIG_PTHREAD_SET_NAME_NP', cc.links(osdep_prefix + '''
     pthread_set_name_np(thread, "QEMU");
     return 0;
   }''', dependencies: threads))
+
+config_host_data.set('CONFIG_PTHREAD_GETNAME_NP', cc.links(osdep_prefix + '''
+  #include <pthread.h>
+
+  int main(void)
+  {
+    char buf[16];
+    pthread_getname_np(pthread_self(), buf, sizeof(buf));
+    return 0;
+  }''', dependencies: threads))
+config_host_data.set('CONFIG_PTHREAD_GET_NAME_NP', cc.links(osdep_prefix + '''
+  #include <pthread.h>
+  #include <pthread_np.h>
+
+  int main(void)
+  {
+    char buf[16];
+    pthread_get_name_np(pthread_self(), buf, sizeof(buf));
+    return 0;
+  }''', dependencies: threads))
+
 config_host_data.set('CONFIG_PTHREAD_CONDATTR_SETCLOCK', cc.links(osdep_prefix + '''
   #include <pthread.h>
 
diff --git a/util/qemu-thread-posix.c b/util/qemu-thread-posix.c
index 275445ed94..fbb94ca97b 100644
--- a/util/qemu-thread-posix.c
+++ b/util/qemu-thread-posix.c
@@ -18,7 +18,7 @@
 #include "qemu/tsan.h"
 #include "qemu/bitmap.h"
 
-#ifdef CONFIG_PTHREAD_SET_NAME_NP
+#if defined(CONFIG_PTHREAD_SET_NAME_NP) || defined(CONFIG_PTHREAD_GET_NAME_NP)
 #include <pthread_np.h>
 #endif
 
@@ -532,3 +532,29 @@ void *qemu_thread_join(QemuThread *thread)
     }
     return ret;
 }
+
+#ifndef PTHREAD_MAX_NAMELEN_NP
+#define PTHREAD_MAX_NAMELEN_NP 16
+#endif
+
+static __thread char namebuf[PTHREAD_MAX_NAMELEN_NP];
+
+const char *qemu_thread_get_name(void)
+{
+    int rv;
+    if (namebuf[0] != '\0') {
+        return namebuf;
+    }
+
+# if defined(CONFIG_PTHREAD_GETNAME_NP)
+    rv = pthread_getname_np(pthread_self(), namebuf, sizeof(namebuf));
+# elif defined(CONFIG_PTHREAD_GET_NAME_NP)
+    rv = pthread_get_name_np(pthread_self(), namebuf, sizeof(namebuf));
+# else
+    rv = -1;
+# endif
+    if (rv != 0) {
+        strlcpy(namebuf, "unnamed", G_N_ELEMENTS(namebuf));
+    }
+    return namebuf;
+}
diff --git a/util/qemu-thread-win32.c b/util/qemu-thread-win32.c
index 7a734a7a09..e3789c20d1 100644
--- a/util/qemu-thread-win32.c
+++ b/util/qemu-thread-win32.c
@@ -19,7 +19,10 @@
 
 typedef HRESULT (WINAPI *pSetThreadDescription) (HANDLE hThread,
                                                  PCWSTR lpThreadDescription);
+typedef HRESULT (WINAPI *pGetThreadDescription) (HANDLE hThread,
+                                                 PWSTR *lpThreadDescription);
 static pSetThreadDescription SetThreadDescriptionFunc;
+static pGetThreadDescription GetThreadDescriptionFunc;
 static HMODULE kernel32_module;
 
 static void __attribute__((__constructor__(QEMU_CONSTRUCTOR_EARLY)))
@@ -28,7 +31,7 @@ qemu_thread_init(void)
     qemu_thread_set_name("main");
 }
 
-static bool load_set_thread_description(void)
+static bool load_thread_description(void)
 {
     static gsize _init_once = 0;
 
@@ -38,14 +41,17 @@ static bool load_set_thread_description(void)
             SetThreadDescriptionFunc =
                 (pSetThreadDescription)GetProcAddress(kernel32_module,
                                                       "SetThreadDescription");
-            if (!SetThreadDescriptionFunc) {
+            GetThreadDescriptionFunc =
+                (pGetThreadDescription)GetProcAddress(kernel32_module,
+                                                      "GetThreadDescription");
+            if (!SetThreadDescriptionFunc || !GetThreadDescriptionFunc) {
                 FreeLibrary(kernel32_module);
             }
         }
         g_once_init_leave(&_init_once, 1);
     }
 
-    return !!SetThreadDescriptionFunc;
+    return !!(SetThreadDescriptionFunc && GetThreadDescriptionFunc);
 }
 
 static void error_exit(int err, const char *msg)
@@ -326,7 +332,7 @@ void qemu_thread_set_name(const char *name)
 {
     g_autofree wchar_t *namew = NULL;
 
-    if (!load_set_thread_description()) {
+    if (!load_thread_description()) {
         return;
     }
 
@@ -412,3 +418,38 @@ bool qemu_thread_is_self(QemuThread *thread)
 {
     return GetCurrentThreadId() == thread->tid;
 }
+
+static __thread char namebuf[64];
+
+const char *qemu_thread_get_name(void)
+{
+    HRESULT hr;
+    wchar_t *namew = NULL;
+    g_autofree char *name = NULL;
+
+    if (namebuf[0] != '\0') {
+        return namebuf;
+    }
+
+    if (!load_thread_description()) {
+        goto error;
+    }
+
+    hr = GetThreadDescriptionFunc(GetCurrentThread(), &namew);
+    if (!SUCCEEDED(hr)) {
+        goto error;
+    }
+
+    name = g_utf16_to_utf8(namew, -1, NULL, NULL, NULL);
+    LocalFree(namew);
+    if (!name) {
+        goto error;
+    }
+
+    g_strlcpy(namebuf, name, G_N_ELEMENTS(namebuf));
+    return namebuf;
+
+ error:
+    strlcpy(namebuf, "unnamed", G_N_ELEMENTS(namebuf));
+    return namebuf;
+}
-- 
2.50.1

[PATCH v2 08/14] log: avoid prefix on split qemu_log calls

[Daniel P. Berrangé]

Some code makes multiple qemu_log calls to incrementally emit
a single message. Currently timestamps get prepended to all
qemu_log calls, even those continuing a previous incomplete
message.

This changes the qemu_log so it skips adding a new line prefix,
if the previous qemu_log call did NOT end with a newline.

Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 util/log.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/util/log.c b/util/log.c
index abdcb6b311..2642a55c59 100644
--- a/util/log.c
+++ b/util/log.c
@@ -143,6 +143,12 @@ void qemu_log_unlock(FILE *logfile)
     }
 }
 
+/*
+ * 'true' if the previous log message lacked a trailing '\n',
+ * and thus the subsequent call must skip any prefix
+ */
+static __thread bool incomplete;
+
 void qemu_log(const char *fmt, ...)
 {
     FILE *f;
@@ -154,7 +160,7 @@ void qemu_log(const char *fmt, ...)
      * was emitted if we are delayed acquiring the
      * mutex
      */
-    if (message_with_timestamp) {
+    if (message_with_timestamp && !incomplete) {
         g_autoptr(GDateTime) dt = g_date_time_new_now_utc();
         timestr = g_date_time_format_iso8601(dt);
     }
@@ -170,6 +176,7 @@ void qemu_log(const char *fmt, ...)
         va_start(ap, fmt);
         vfprintf(f, fmt, ap);
         va_end(ap);
+        incomplete = fmt[strlen(fmt) - 1] != '\n';
         qemu_log_unlock(f);
     }
 }
-- 
2.50.1

[PATCH v2 09/14] util: introduce common helper for error-report & log code

[Daniel P. Berrangé]

The error-report and log code both have a need to add prefixes
to messages they are printing, with the current example being
a timestamp.

The format and configuration they use should be consistent, so
providing a common helper will ensure this is always the case.
Initially the helper only emits a timestamp, but future patches
will expand this.

This takes the liberty of assigning the new file to the same
maintainer as the existing error-report.c file, given it will
be extracting some functionality from the latter.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 MAINTAINERS            |  2 ++
 include/qemu/message.h | 40 ++++++++++++++++++++++++++++++++++++++++
 util/meson.build       |  1 +
 util/message.c         | 36 ++++++++++++++++++++++++++++++++++++
 4 files changed, 79 insertions(+)
 create mode 100644 include/qemu/message.h
 create mode 100644 util/message.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 8f074e4371..851d97b846 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -3176,9 +3176,11 @@ M: Markus Armbruster <armbru@redhat.com>
 S: Supported
 F: include/qapi/error.h
 F: include/qemu/error-report.h
+F: include/qemu/message.h
 F: qapi/error.json
 F: util/error.c
 F: util/error-report.c
+F: util/message.c
 F: scripts/coccinelle/err-bad-newline.cocci
 F: scripts/coccinelle/error-use-after-free.cocci
 F: scripts/coccinelle/error_propagate_null.cocci
diff --git a/include/qemu/message.h b/include/qemu/message.h
new file mode 100644
index 0000000000..160bee8417
--- /dev/null
+++ b/include/qemu/message.h
@@ -0,0 +1,40 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#ifndef QEMU_MESSAGE_H
+#define QEMU_MESSAGE_H
+
+enum QMessageFormatFlags {
+    QMESSAGE_FORMAT_TIMESTAMP = (1 << 0),
+};
+
+/*
+ * qmessage_set_format:
+ * @flags: the message information to emit
+ *
+ * Select which pieces of information to
+ * emit for messages
+ */
+void qmessage_set_format(int flags);
+
+enum QMessageContextFlags {
+    QMESSAGE_CONTEXT_SKIP_MONITOR = (1 << 0),
+};
+
+/*
+ * qmessage_context:
+ * @flags: the message formatting control flags
+ *
+ * Format a message prefix with the information
+ * previously selected by a call to
+ * qmessage_set_format.
+ *
+ * If @flags contains QMESSAGE_CONTEXT_SKIP_MONITOR
+ * an empty string will be returned if running in
+ * the context of a HMP command
+ *
+ * Returns: a formatted message prefix, or empty string;
+ * to be freed by the caller.
+ */
+char *qmessage_context(int flags);
+
+#endif /* QEMU_MESSAGE_H */
diff --git a/util/meson.build b/util/meson.build
index 35029380a3..f5365e3b4f 100644
--- a/util/meson.build
+++ b/util/meson.build
@@ -40,6 +40,7 @@ util_ss.add(files('host-utils.c'))
 util_ss.add(files('bitmap.c', 'bitops.c'))
 util_ss.add(files('fifo8.c'))
 util_ss.add(files('cacheflush.c'))
+util_ss.add(files('message.c'))
 util_ss.add(files('error.c', 'error-report.c'))
 util_ss.add(files('qemu-print.c'))
 util_ss.add(files('id.c'))
diff --git a/util/message.c b/util/message.c
new file mode 100644
index 0000000000..1052a2d6aa
--- /dev/null
+++ b/util/message.c
@@ -0,0 +1,36 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#include "qemu/osdep.h"
+
+#include "qemu/message.h"
+#include "monitor/monitor.h"
+
+static int message_format;
+
+void qmessage_set_format(int flags)
+{
+    message_format = flags;
+}
+
+char *qmessage_context(int flags)
+{
+    g_autofree char *timestr = NULL;
+
+    if ((flags & QMESSAGE_CONTEXT_SKIP_MONITOR) &&
+        monitor_cur()) {
+        return NULL;
+    }
+
+    if (message_format & QMESSAGE_FORMAT_TIMESTAMP) {
+        g_autoptr(GDateTime) dt = g_date_time_new_now_utc();
+        timestr = g_date_time_format_iso8601(dt);
+    }
+
+    if (!timestr) {
+        return NULL;
+    }
+
+    return g_strdup_printf("%s%s",
+                           timestr ? timestr : "",
+                           timestr ? " " : "");
+}
-- 
2.50.1

[PATCH v2 10/14] util: convert error-report & log to message API for timestamp

[Daniel P. Berrangé]

Both the error-report and log APIs can optional emit a timestamp
as a prefix on messages, with the '-msg timestamp=on' command
line flag is set.

Convert them to the new message API for formatting the context
prefix, guaranteeign they will have matching behaviour going
forward.

There is no change in output format for either logs or errors
with this conversion.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 include/qemu/error-report.h    |  1 -
 system/vl.c                    |  7 ++++++-
 tests/unit/test-error-report.c |  3 ++-
 util/error-report.c            | 18 ++++--------------
 util/log.c                     | 21 +++++++++------------
 5 files changed, 21 insertions(+), 29 deletions(-)

diff --git a/include/qemu/error-report.h b/include/qemu/error-report.h
index 3ae2357fda..c8000778ec 100644
--- a/include/qemu/error-report.h
+++ b/include/qemu/error-report.h
@@ -70,7 +70,6 @@ void error_init(const char *argv0);
                               fmt, ##__VA_ARGS__);      \
     })
 
-extern bool message_with_timestamp;
 extern bool error_with_guestname;
 extern const char *error_guest_name;
 
diff --git a/system/vl.c b/system/vl.c
index a64fd90d4a..696dd92669 100644
--- a/system/vl.c
+++ b/system/vl.c
@@ -26,6 +26,7 @@
 #include "qemu/help-texts.h"
 #include "qemu/datadir.h"
 #include "qemu/units.h"
+#include "qemu/message.h"
 #include "qemu/module.h"
 #include "qemu/target-info.h"
 #include "exec/cpu-common.h"
@@ -813,8 +814,12 @@ static void realtime_init(void)
 
 static void configure_msg(QemuOpts *opts)
 {
-    message_with_timestamp = qemu_opt_get_bool(opts, "timestamp", false);
+    int flags = 0;
+    if (qemu_opt_get_bool(opts, "timestamp", false)) {
+        flags |= QMESSAGE_FORMAT_TIMESTAMP;
+    }
     error_with_guestname = qemu_opt_get_bool(opts, "guest-name", false);
+    qmessage_set_format(flags);
 }
 
 
diff --git a/tests/unit/test-error-report.c b/tests/unit/test-error-report.c
index 54319c86c9..78f8b57660 100644
--- a/tests/unit/test-error-report.c
+++ b/tests/unit/test-error-report.c
@@ -13,6 +13,7 @@
 
 #include "qemu/error-report.h"
 #include "qapi/error.h"
+#include "qemu/message.h"
 
 static void
 test_error_report_simple(void)
@@ -90,7 +91,7 @@ static void
 test_error_report_timestamp(void)
 {
     if (g_test_subprocess()) {
-        message_with_timestamp = true;
+        qmessage_set_format(QMESSAGE_FORMAT_TIMESTAMP);
         warn_report("warn");
         error_report("err");
         return;
diff --git a/util/error-report.c b/util/error-report.c
index 1b17c11de1..9ee164b1dd 100644
--- a/util/error-report.c
+++ b/util/error-report.c
@@ -13,6 +13,7 @@
 #include "qemu/osdep.h"
 #include "monitor/monitor.h"
 #include "qemu/error-report.h"
+#include "qemu/message.h"
 
 /*
  * @report_type is the type of message: error, warning or
@@ -24,8 +25,6 @@ typedef enum {
     REPORT_TYPE_INFO,
 } report_type;
 
-/* Prepend timestamp to messages */
-bool message_with_timestamp;
 bool error_with_guestname;
 const char *error_guest_name;
 
@@ -169,13 +168,6 @@ static void print_loc(void)
     }
 }
 
-static char *
-real_time_iso8601(void)
-{
-    g_autoptr(GDateTime) dt = g_date_time_new_now_utc();
-    return g_date_time_format_iso8601(dt);
-}
-
 /*
  * Print a message to current monitor if we have one, else to stderr.
  * @report_type is the type of message: error, warning or informational.
@@ -186,12 +178,10 @@ real_time_iso8601(void)
 G_GNUC_PRINTF(2, 0)
 static void vreport(report_type type, const char *fmt, va_list ap)
 {
-    gchar *timestr;
+    g_autofree gchar *context = qmessage_context(QMESSAGE_CONTEXT_SKIP_MONITOR);
 
-    if (message_with_timestamp && !monitor_cur()) {
-        timestr = real_time_iso8601();
-        error_printf("%s ", timestr);
-        g_free(timestr);
+    if (context != NULL) {
+        error_printf("%s", context);
     }
 
     /* Only prepend guest name if -msg guest-name and -name guest=... are set */
diff --git a/util/log.c b/util/log.c
index 2642a55c59..fc900cde0c 100644
--- a/util/log.c
+++ b/util/log.c
@@ -22,6 +22,7 @@
 #include "qemu/range.h"
 #include "qemu/error-report.h"
 #include "qapi/error.h"
+#include "qemu/message.h"
 #include "qemu/cutils.h"
 #include "trace/control.h"
 #include "qemu/thread.h"
@@ -152,25 +153,21 @@ static __thread bool incomplete;
 void qemu_log(const char *fmt, ...)
 {
     FILE *f;
-    g_autofree const char *timestr = NULL;
-
     /*
-     * Prepare the timestamp *outside* the logging
-     * lock so it better reflects when the message
-     * was emitted if we are delayed acquiring the
-     * mutex
+     * Prepare the context *outside* the logging
+     * lock so any timestamp better reflects when
+     * the message was emitted if we are delayed
+     * acquiring the mutex
      */
-    if (message_with_timestamp && !incomplete) {
-        g_autoptr(GDateTime) dt = g_date_time_new_now_utc();
-        timestr = g_date_time_format_iso8601(dt);
-    }
+    g_autofree const char *context =
+        incomplete ? NULL : qmessage_context(0);
 
     f = qemu_log_trylock();
     if (f) {
         va_list ap;
 
-        if (timestr) {
-            fprintf(f, "%s ", timestr);
+        if (context != NULL) {
+            fwrite(context, 1, strlen(context), f);
         }
 
         va_start(ap, fmt);
-- 
2.50.1

[PATCH v2 11/14] util: add support for formatting a workload name in messages

[Daniel P. Berrangé]

The error_report function can include the guest name in any
messages it prints. The qemu_log function has no equivalent
behaviour.

This introduces support for a "workload name" in the new
messages API, which in the case of system emulators will
be the guest name. The possibility of defining a workload
name for other binaries is left as an exercise for the
future.

This change has no impact on the output of the error_report
function, but will change the qemu_log function. This can
be easily seen with the 'log' trace backend, and how it is
now more closely matching error_report output.

Before:

  # qemu-system-x86_64 -msg guest-name=on -name blah -object tls-creds-x509,id=t0,dir=fish -d 'trace:qcrypto*'
  qcrypto_tls_creds_x509_load TLS creds x509 load creds=0x55b3af3fd870 dir=fish
  qcrypto_tls_creds_get_path TLS creds path creds=0x55b3af3fd870 filename=ca-cert.pem path=<none>
  blah qemu-system-x86_64: Unable to access credentials fish/ca-cert.pem: No such file or directory

After:

  # qemu-system-x86_64 -msg guest-name=on -name blah -object tls-creds-x509,id=t0,dir=fish -d 'trace:qcrypto*'
  blah qcrypto_tls_creds_x509_load TLS creds x509 load creds=0x55b3af3fd870 dir=fish
  blah qcrypto_tls_creds_get_path TLS creds path creds=0x55b3af3fd870 filename=ca-cert.pem path=<none>
  blah qemu-system-x86_64: Unable to access credentials fish/ca-cert.pem: No such file or directory

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 include/qemu/error-report.h |  3 ---
 include/qemu/message.h      | 14 ++++++++++++--
 system/vl.c                 |  6 ++++--
 util/error-report.c         |  7 -------
 util/message.c              | 21 ++++++++++++++++++---
 5 files changed, 34 insertions(+), 17 deletions(-)

diff --git a/include/qemu/error-report.h b/include/qemu/error-report.h
index c8000778ec..ffc305f828 100644
--- a/include/qemu/error-report.h
+++ b/include/qemu/error-report.h
@@ -70,7 +70,4 @@ void error_init(const char *argv0);
                               fmt, ##__VA_ARGS__);      \
     })
 
-extern bool error_with_guestname;
-extern const char *error_guest_name;
-
 #endif
diff --git a/include/qemu/message.h b/include/qemu/message.h
index 160bee8417..95fab69424 100644
--- a/include/qemu/message.h
+++ b/include/qemu/message.h
@@ -5,9 +5,10 @@
 
 enum QMessageFormatFlags {
     QMESSAGE_FORMAT_TIMESTAMP = (1 << 0),
+    QMESSAGE_FORMAT_WORKLOAD_NAME = (1 << 1),
 };
 
-/*
+/**
  * qmessage_set_format:
  * @flags: the message information to emit
  *
@@ -16,11 +17,20 @@ enum QMessageFormatFlags {
  */
 void qmessage_set_format(int flags);
 
+/**
+ * qmessage_set_workload_name:
+ * @name: the name of the workload
+ *
+ * Set the workload name, which for a system emulator
+ * will be the guest VM name.
+ */
+void qmessage_set_workload_name(const char *name);
+
 enum QMessageContextFlags {
     QMESSAGE_CONTEXT_SKIP_MONITOR = (1 << 0),
 };
 
-/*
+/**
  * qmessage_context:
  * @flags: the message formatting control flags
  *
diff --git a/system/vl.c b/system/vl.c
index 696dd92669..fee6fdf7b1 100644
--- a/system/vl.c
+++ b/system/vl.c
@@ -818,7 +818,9 @@ static void configure_msg(QemuOpts *opts)
     if (qemu_opt_get_bool(opts, "timestamp", false)) {
         flags |= QMESSAGE_FORMAT_TIMESTAMP;
     }
-    error_with_guestname = qemu_opt_get_bool(opts, "guest-name", false);
+    if (qemu_opt_get_bool(opts, "guest-name", false)) {
+        flags |= QMESSAGE_FORMAT_WORKLOAD_NAME;
+    }
     qmessage_set_format(flags);
 }
 
@@ -3520,7 +3522,7 @@ void qemu_init(int argc, char **argv)
                     exit(1);
                 }
                 /* Capture guest name if -msg guest-name is used later */
-                error_guest_name = qemu_opt_get(opts, "guest");
+                qmessage_set_workload_name(qemu_opt_get(opts, "guest"));
                 break;
             case QEMU_OPTION_prom_env:
                 if (nb_prom_envs >= MAX_PROM_ENVS) {
diff --git a/util/error-report.c b/util/error-report.c
index 9ee164b1dd..37c803f69f 100644
--- a/util/error-report.c
+++ b/util/error-report.c
@@ -25,8 +25,6 @@ typedef enum {
     REPORT_TYPE_INFO,
 } report_type;
 
-bool error_with_guestname;
-const char *error_guest_name;
 
 int error_printf(const char *fmt, ...)
 {
@@ -184,11 +182,6 @@ static void vreport(report_type type, const char *fmt, va_list ap)
         error_printf("%s", context);
     }
 
-    /* Only prepend guest name if -msg guest-name and -name guest=... are set */
-    if (error_with_guestname && error_guest_name && !monitor_cur()) {
-        error_printf("%s ", error_guest_name);
-    }
-
     print_loc();
 
     switch (type) {
diff --git a/util/message.c b/util/message.c
index 1052a2d6aa..0ec9a56d21 100644
--- a/util/message.c
+++ b/util/message.c
@@ -6,15 +6,24 @@
 #include "monitor/monitor.h"
 
 static int message_format;
+static char *message_workloadname;
 
 void qmessage_set_format(int flags)
 {
     message_format = flags;
 }
 
+
+void qmessage_set_workload_name(const char *name)
+{
+    message_workloadname = g_strdup(name);
+}
+
+
 char *qmessage_context(int flags)
 {
     g_autofree char *timestr = NULL;
+    const char *wknamestr = NULL;
 
     if ((flags & QMESSAGE_CONTEXT_SKIP_MONITOR) &&
         monitor_cur()) {
@@ -26,11 +35,17 @@ char *qmessage_context(int flags)
         timestr = g_date_time_format_iso8601(dt);
     }
 
-    if (!timestr) {
+    if (message_format & QMESSAGE_FORMAT_WORKLOAD_NAME) {
+        wknamestr = message_workloadname;
+    }
+
+    if (!timestr && !wknamestr) {
         return NULL;
     }
 
-    return g_strdup_printf("%s%s",
+    return g_strdup_printf("%s%s%s%s",
                            timestr ? timestr : "",
-                           timestr ? " " : "");
+                           timestr ? " " : "",
+                           wknamestr ? wknamestr : "",
+                           wknamestr ? " " : "");
 }
-- 
2.50.1

[PATCH v2 12/14] util: add support for formatting a program name in messages

[Daniel P. Berrangé]

The error_report function can include the program name in any
messages it prints. The qemu_log function has no equivalent
behaviour.

This introduces support for a "program name" in the new
messages API, which will be included by default for all
binaries.

This change tweaks the output of the error_report function,
adding a space between the program name and the location
info. The qemu_log function will gain the program name. This
can be easily seen with the 'log' trace backend, and how it
is now more closely matching error_report output.

Before:

  # qemu-system-x86_64 -object tls-creds-x509,id=t0,dir=fish -d 'trace:qcrypto*'
  qcrypto_tls_creds_x509_load TLS creds x509 load creds=0x5584e13937f0 dir=fish
  qcrypto_tls_creds_get_path TLS creds path creds=0x5584e13937f0 filename=ca-cert.pem path=<none>
  qemu-system-x86_64: Unable to access credentials fish/ca-cert.pem: No such file or directory

After:

  # qemu-system-x86_64 -object tls-creds-x509,id=t0,dir=fish -d 'trace:qcrypto*'
  qemu-system-x86_64: qcrypto_tls_creds_x509_load TLS creds x509 load creds=0x5584e13937f0 dir=fish
  qemu-system-x86_64: qcrypto_tls_creds_get_path TLS creds path creds=0x5584e13937f0 filename=ca-cert.pem path=<none>
  qemu-system-x86_64: Unable to access credentials fish/ca-cert.pem: No such file or directory

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 include/qemu/message.h         |  1 +
 system/vl.c                    |  2 +-
 tests/unit/test-error-report.c |  5 +++--
 util/error-report.c            |  4 ----
 util/message.c                 | 15 +++++++++++----
 5 files changed, 16 insertions(+), 11 deletions(-)

diff --git a/include/qemu/message.h b/include/qemu/message.h
index 95fab69424..4550ce8ed7 100644
--- a/include/qemu/message.h
+++ b/include/qemu/message.h
@@ -6,6 +6,7 @@
 enum QMessageFormatFlags {
     QMESSAGE_FORMAT_TIMESTAMP = (1 << 0),
     QMESSAGE_FORMAT_WORKLOAD_NAME = (1 << 1),
+    QMESSAGE_FORMAT_PROGRAM_NAME = (1 << 2),
 };
 
 /**
diff --git a/system/vl.c b/system/vl.c
index fee6fdf7b1..9030212c50 100644
--- a/system/vl.c
+++ b/system/vl.c
@@ -814,7 +814,7 @@ static void realtime_init(void)
 
 static void configure_msg(QemuOpts *opts)
 {
-    int flags = 0;
+    int flags = QMESSAGE_FORMAT_PROGRAM_NAME;
     if (qemu_opt_get_bool(opts, "timestamp", false)) {
         flags |= QMESSAGE_FORMAT_TIMESTAMP;
     }
diff --git a/tests/unit/test-error-report.c b/tests/unit/test-error-report.c
index 78f8b57660..3987a8ed25 100644
--- a/tests/unit/test-error-report.c
+++ b/tests/unit/test-error-report.c
@@ -48,7 +48,7 @@ test_error_report_loc(void)
     g_test_trap_subprocess(NULL, 0, 0);
     g_test_trap_assert_passed();
     g_test_trap_assert_stderr("\
-test-error-report:some-file.c:7717: test error1*\
+test-error-report: some-file.c:7717: test error1*\
 test-error-report: test error2*\
 ");
 }
@@ -91,7 +91,8 @@ static void
 test_error_report_timestamp(void)
 {
     if (g_test_subprocess()) {
-        qmessage_set_format(QMESSAGE_FORMAT_TIMESTAMP);
+        qmessage_set_format(QMESSAGE_FORMAT_TIMESTAMP |
+                            QMESSAGE_FORMAT_PROGRAM_NAME);
         warn_report("warn");
         error_report("err");
         return;
diff --git a/util/error-report.c b/util/error-report.c
index 37c803f69f..2e58ee1c50 100644
--- a/util/error-report.c
+++ b/util/error-report.c
@@ -141,10 +141,6 @@ static void print_loc(void)
     int i;
     const char *const *argp;
 
-    if (!monitor_cur() && g_get_prgname()) {
-        error_printf("%s:", g_get_prgname());
-        sep = " ";
-    }
     switch (cur_loc->kind) {
     case LOC_CMDLINE:
         argp = cur_loc->ptr;
diff --git a/util/message.c b/util/message.c
index 0ec9a56d21..cb3ffd6700 100644
--- a/util/message.c
+++ b/util/message.c
@@ -5,7 +5,7 @@
 #include "qemu/message.h"
 #include "monitor/monitor.h"
 
-static int message_format;
+static int message_format = QMESSAGE_FORMAT_PROGRAM_NAME;
 static char *message_workloadname;
 
 void qmessage_set_format(int flags)
@@ -24,6 +24,7 @@ char *qmessage_context(int flags)
 {
     g_autofree char *timestr = NULL;
     const char *wknamestr = NULL;
+    const char *pgnamestr = NULL;
 
     if ((flags & QMESSAGE_CONTEXT_SKIP_MONITOR) &&
         monitor_cur()) {
@@ -39,13 +40,19 @@ char *qmessage_context(int flags)
         wknamestr = message_workloadname;
     }
 
-    if (!timestr && !wknamestr) {
+    if (message_format & QMESSAGE_FORMAT_PROGRAM_NAME) {
+        pgnamestr = g_get_prgname();
+    }
+
+    if (!timestr && !wknamestr && !pgnamestr) {
         return NULL;
     }
 
-    return g_strdup_printf("%s%s%s%s",
+    return g_strdup_printf("%s%s%s%s%s%s",
                            timestr ? timestr : "",
                            timestr ? " " : "",
                            wknamestr ? wknamestr : "",
-                           wknamestr ? " " : "");
+                           wknamestr ? " " : "",
+                           pgnamestr ? pgnamestr : "",
+                           pgnamestr ? ": " : "");
 }
-- 
2.50.1

[PATCH v2 13/14] util: add support for formatting thread info in messages

[Daniel P. Berrangé]

The message context is now extended to be able to include the
thread ID and thread name, after the program name. On Linux
the thread ID will match the process TID visible in /proc,
while on other platforms it will merely be an integer repr
of the system thread object address/ID.

This changes the output for both error_report and qemu_log,
when running under the system emulators or the QEMU storage
daemon. Other programs omit the thread information since
they are largely single threaded, though potentially it
would be useful to enable in all of them, given that the RCU
thread will always get spawned by a constructor function.

Before:

  # qemu-system-x86_64 -object tls-creds-x509,id=t0,dir=fish -d 'trace:qcrypto*'
  qemu-system-x86_64: qcrypto_tls_creds_x509_load TLS creds x509 load creds=0x560db818e080 dir=fish
  qemu-system-x86_64: qcrypto_tls_creds_get_path TLS creds path creds=0x560db818e080 filename=ca-cert.pem path=<none>
  qemu-system-x86_64: Unable to access credentials fish/ca-cert.pem: No such file or directory

After:

  # qemu-system-x86_64 -object tls-creds-x509,id=t0,dir=fish -d 'trace:qcrypto*'
  qemu-system-x86_64(772366:main): qcrypto_tls_creds_x509_load TLS creds x509 load creds=0x560db818e080 dir=fish
  qemu-system-x86_64(772366:main): qcrypto_tls_creds_get_path TLS creds path creds=0x560db818e080 filename=ca-cert.pem path=<none>
  qemu-system-x86_64(772366:main): Unable to access credentials fish/ca-cert.pem: No such file or directory

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 include/qemu/message.h               |  1 +
 storage-daemon/qemu-storage-daemon.c |  6 +++++
 system/vl.c                          |  8 +++++--
 tests/qemu-iotests/041               |  2 +-
 tests/qemu-iotests/common.filter     |  2 +-
 util/message.c                       | 33 +++++++++++++++++++---------
 6 files changed, 38 insertions(+), 14 deletions(-)

diff --git a/include/qemu/message.h b/include/qemu/message.h
index 4550ce8ed7..6dbb068ca9 100644
--- a/include/qemu/message.h
+++ b/include/qemu/message.h
@@ -7,6 +7,7 @@ enum QMessageFormatFlags {
     QMESSAGE_FORMAT_TIMESTAMP = (1 << 0),
     QMESSAGE_FORMAT_WORKLOAD_NAME = (1 << 1),
     QMESSAGE_FORMAT_PROGRAM_NAME = (1 << 2),
+    QMESSAGE_FORMAT_THREAD_INFO = (1 << 3),
 };
 
 /**
diff --git a/storage-daemon/qemu-storage-daemon.c b/storage-daemon/qemu-storage-daemon.c
index eb72561358..cc44ed7848 100644
--- a/storage-daemon/qemu-storage-daemon.c
+++ b/storage-daemon/qemu-storage-daemon.c
@@ -47,6 +47,7 @@
 #include "qemu/cutils.h"
 #include "qemu/config-file.h"
 #include "qemu/error-report.h"
+#include "qemu/message.h"
 #include "qemu/help_option.h"
 #include "qemu/job.h"
 #include "qemu/log.h"
@@ -65,6 +66,10 @@ static const char *pid_file;
 static char *pid_file_realpath;
 static volatile bool exit_requested = false;
 
+#define QMESSAGE_FORMAT_DEFAULT \
+    (QMESSAGE_FORMAT_PROGRAM_NAME | \
+     QMESSAGE_FORMAT_THREAD_INFO)
+
 void qemu_system_killed(int signal, pid_t pid)
 {
     exit_requested = true;
@@ -399,6 +404,7 @@ int main(int argc, char *argv[])
 #endif
 
     error_init(argv[0]);
+    qmessage_set_format(QMESSAGE_FORMAT_DEFAULT);
     qemu_init_exec_dir(argv[0]);
     os_setup_signal_handling();
 
diff --git a/system/vl.c b/system/vl.c
index 9030212c50..20b655a7bc 100644
--- a/system/vl.c
+++ b/system/vl.c
@@ -145,6 +145,10 @@
 
 #define MAX_VIRTIO_CONSOLES 1
 
+#define QMESSAGE_FORMAT_DEFAULT \
+    (QMESSAGE_FORMAT_PROGRAM_NAME | \
+     QMESSAGE_FORMAT_THREAD_INFO)
+
 typedef struct BlockdevOptionsQueueEntry {
     BlockdevOptions *bdo;
     Location loc;
@@ -811,10 +815,9 @@ static void realtime_init(void)
     }
 }
 
-
 static void configure_msg(QemuOpts *opts)
 {
-    int flags = QMESSAGE_FORMAT_PROGRAM_NAME;
+    int flags = QMESSAGE_FORMAT_DEFAULT;
     if (qemu_opt_get_bool(opts, "timestamp", false)) {
         flags |= QMESSAGE_FORMAT_TIMESTAMP;
     }
@@ -2888,6 +2891,7 @@ void qemu_init(int argc, char **argv)
     module_call_init(MODULE_INIT_OPTS);
 
     error_init(argv[0]);
+    qmessage_set_format(QMESSAGE_FORMAT_DEFAULT);
     qemu_init_exec_dir(argv[0]);
 
     os_setup_limits();
diff --git a/tests/qemu-iotests/041 b/tests/qemu-iotests/041
index 8452845f44..d9954da42b 100755
--- a/tests/qemu-iotests/041
+++ b/tests/qemu-iotests/041
@@ -1102,7 +1102,7 @@ class TestRepairQuorum(iotests.QMPTestCase):
         self.vm.shutdown()
         log = iotests.filter_qtest(self.vm.get_log())
         log = re.sub(r'^Formatting.*\n', '', log)
-        log = re.sub(r'^%s: ' % os.path.basename(iotests.qemu_prog), '', log)
+        log = re.sub(r'^%s\(.*\): ' % os.path.basename(iotests.qemu_prog), '', log)
 
         self.assertEqual(log,
                          "Can no longer replace 'img1' by 'repair0', because " +
diff --git a/tests/qemu-iotests/common.filter b/tests/qemu-iotests/common.filter
index 511a55b1e8..ecf74c223e 100644
--- a/tests/qemu-iotests/common.filter
+++ b/tests/qemu-iotests/common.filter
@@ -81,7 +81,7 @@ _filter_qemu_io()
 # replace occurrences of QEMU_PROG with "qemu"
 _filter_qemu()
 {
-    gsed -e "s#\\(^\\|(qemu) \\)$(basename $QEMU_PROG):#\1QEMU_PROG:#" \
+    gsed -e "s#\\(^\\|(qemu) \\)$(basename $QEMU_PROG)(.*):#\1QEMU_PROG:#" \
         -e 's#^QEMU [0-9]\+\.[0-9]\+\.[0-9]\+ monitor#QEMU X.Y.Z monitor#' \
         -e $'s#\r##' # QEMU monitor uses \r\n line endings
 }
diff --git a/util/message.c b/util/message.c
index cb3ffd6700..5201ffc569 100644
--- a/util/message.c
+++ b/util/message.c
@@ -44,15 +44,28 @@ char *qmessage_context(int flags)
         pgnamestr = g_get_prgname();
     }
 
-    if (!timestr && !wknamestr && !pgnamestr) {
-        return NULL;
-    }
+    if (message_format & QMESSAGE_FORMAT_THREAD_INFO) {
+        int thid = qemu_get_thread_id();
+        const char *thname = qemu_thread_get_name();
 
-    return g_strdup_printf("%s%s%s%s%s%s",
-                           timestr ? timestr : "",
-                           timestr ? " " : "",
-                           wknamestr ? wknamestr : "",
-                           wknamestr ? " " : "",
-                           pgnamestr ? pgnamestr : "",
-                           pgnamestr ? ": " : "");
+        return g_strdup_printf("%s%s%s%s%s(%d:%s): ",
+                               timestr ? timestr : "",
+                               timestr ? " " : "",
+                               wknamestr ? wknamestr : "",
+                               wknamestr ? " " : "",
+                               pgnamestr ? pgnamestr : "",
+                               thid, thname);
+    } else {
+        if (!timestr && !wknamestr && !pgnamestr) {
+            return NULL;
+        }
+
+        return g_strdup_printf("%s%s%s%s%s%s",
+                               timestr ? timestr : "",
+                               timestr ? " " : "",
+                               wknamestr ? wknamestr : "",
+                               wknamestr ? " " : "",
+                               pgnamestr ? pgnamestr : "",
+                               pgnamestr ? ": " : "");
+    }
 }
-- 
2.50.1

[PATCH v2 14/14] util: add brackets around guest name in message context

[Daniel P. Berrangé]

The message context can optionally include the guest name if the
argument '-msg guest-name=on' is given. The formatting, however,
does not look good if the guest name contains whitespace. Change
the output to include square brackets to demarcate the name.

Before:

  # qemu-system-x86_64 -object tls-creds-x509,id=t0,dir=fish -d 'trace:qcrypto*' -msg guest-name=on -name "fish food"
  fish food qemu-system-x86_64(1146846:main): qcrypto_tls_creds_x509_load TLS creds x509 load creds=0x55657e94e690 dir=fish
  fish food qemu-system-x86_64(1146846:main): qcrypto_tls_creds_get_path TLS creds path creds=0x55657e94e690 filename=ca-cert.pem path=<none>
  fish food qemu-system-x86_64(1146846:main): Unable to access credentials fish/ca-cert.pem: No such file or directory

After:

  # qemu-system-x86_64 -object tls-creds-x509,id=t0,dir=fish -d 'trace:qcrypto*' -msg guest-name=on -name "fish food"
  [fish food] qemu-system-x86_64(1144713:main): qcrypto_tls_creds_x509_load TLS creds x509 load creds=0x5604ada2c950 dir=fish
  [fish food] qemu-system-x86_64(1144713:main): qcrypto_tls_creds_get_path TLS creds path creds=0x5604ada2c950 filename=ca-cert.pem path=<none>
  [fish food] qemu-system-x86_64(1144713:main): Unable to access credentials fish/ca-cert.pem: No such file or directory

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 util/message.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/util/message.c b/util/message.c
index 5201ffc569..6d3580b7be 100644
--- a/util/message.c
+++ b/util/message.c
@@ -48,11 +48,12 @@ char *qmessage_context(int flags)
         int thid = qemu_get_thread_id();
         const char *thname = qemu_thread_get_name();
 
-        return g_strdup_printf("%s%s%s%s%s(%d:%s): ",
+        return g_strdup_printf("%s%s%s%s%s%s(%d:%s): ",
                                timestr ? timestr : "",
                                timestr ? " " : "",
+                               wknamestr ? "[" : "",
                                wknamestr ? wknamestr : "",
-                               wknamestr ? " " : "",
+                               wknamestr ? "] " : "",
                                pgnamestr ? pgnamestr : "",
                                thid, thname);
     } else {
@@ -60,11 +61,12 @@ char *qmessage_context(int flags)
             return NULL;
         }
 
-        return g_strdup_printf("%s%s%s%s%s%s",
+        return g_strdup_printf("%s%s%s%s%s%s%s",
                                timestr ? timestr : "",
                                timestr ? " " : "",
+                               wknamestr ? "[" : "",
                                wknamestr ? wknamestr : "",
-                               wknamestr ? " " : "",
+                               wknamestr ? "] " : "",
                                pgnamestr ? pgnamestr : "",
                                pgnamestr ? ": " : "");
     }
-- 
2.50.1

Re: [PATCH v2 01/14] include: define constant for early constructor priority

[Richard Henderson]

On 8/30/25 04:03, Daniel P. Berrangé wrote:
> Functions marked with __attribute__((__constructor__)) will be
> invoked in linker order. In theory this is well defined, but
> in practice, it is hard to determine what this order will be
> with the layers of indirection through meson, ninja and the
> static libraries QEMU builds.
> 
> Notably, the order currently appears different between Linux
> and Windows (as tested with Wine on Linux). This can cause
> problems when certain QEMU constructors have a dependancy on
> other QEMU constructors.
> 
> To address this define a QEMU_CONSTRUCTOR_EARLY constant which
> provides a priority value that will run before other default
> constructors. This is to be used for QEMU constructors that
> are themselves self-contained, but may be relied upon by other
> constructors.
> 
> Signed-off-by: Daniel P. Berrangé<berrange@redhat.com>
> ---
>   include/qemu/compiler.h | 8 ++++++++
>   1 file changed, 8 insertions(+)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

r~

Re: [PATCH v2 02/14] monitor: initialize global data from a constructor

[Richard Henderson]

On 8/30/25 04:03, Daniel P. Berrangé wrote:
> Some monitor functions, most notably, monitor_cur() rely on global
> data being initialized by 'monitor_init_globals()'. The latter is
> called relatively late in startup. If code triggers error_report()
> before monitor_init_globals() is called, QEMU will abort when
> accessing the uninitialized monitor mutex.
> 
> The critical monitor global data must be initialized from a
> constructor function, to improve the guarantee that it is done
> before any possible calls to monitor_cur(). Not only that, but
> the constructor must be marked to run before the default
> constructor in case any of them trigger error reporting.
> 
> Note in particular that the RCU constructor will spawn a background
> thread so we might even have non-constructor QEMU code running
> concurrently with other constructors.
> 
> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
> ---
>   monitor/monitor.c | 14 +++++++++-----
>   1 file changed, 9 insertions(+), 5 deletions(-)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


r~

Re: [PATCH v2 03/14] system: unconditionally enable thread naming

[Richard Henderson]

On 8/30/25 04:03, Daniel P. Berrangé wrote:
> When thread naming was introduced years ago, it was disabled by
> default and put behind a command line flag:
> 
>    commit 8f480de0c91a18d550721f8d9af969ebfbda0793
>    Author: Dr. David Alan Gilbert<dgilbert@redhat.com>
>    Date:   Thu Jan 30 10:20:31 2014 +0000
> 
>      Add 'debug-threads' suboption to --name
> 
> This was done based on a concern that something might depend
> on the historical thread naming. Thread names, however, were
> never promised to be part of QEMU's public API. The defaults
> will vary across platforms, so no assumptions should ever be
> made about naming.
> 
> An opt-in behaviour is also unfortunately incompatible with
> RCU which creates its thread from an constructor function
> which is run before command line args are parsed. Thus the
> RCU thread lacks any name.
> 
> libvirt has unconditionally enabled debug-threads=yes on all
> VMs it creates for 10 years. Interestingly this DID expose a
> bug in libvirt, as it parsed/proc/$PID/stat and could not
> cope with a space in the thread name. This was a latent
> pre-existing bug in libvirt though, and not a part of QEMU's
> API.
> 
> Having thread names always available, will allow thread names
> to be included in error reports and log messags QEMU prints
> by default, which will improve ability to triage QEMU bugs.
> 
> Reviewed-by: Dr. David Alan Gilbert<dave@treblig.org>
> Signed-off-by: Daniel P. Berrangé<berrange@redhat.com>
> ---
>   docs/about/deprecated.rst |  7 +++++++
>   include/qemu/thread.h     |  1 -
>   system/vl.c               | 11 ++++++-----
>   util/qemu-thread-posix.c  | 18 +-----------------
>   util/qemu-thread-win32.c  | 27 ++++++---------------------
>   5 files changed, 20 insertions(+), 44 deletions(-)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

r~

Re: [PATCH v2 04/14] util: expose qemu_thread_set_name

[Richard Henderson]

On 8/30/25 04:03, Daniel P. Berrangé wrote:
> The ability to set the thread name needs to be used in a number
> of places, so expose the current impls as public methods.
> 
> Signed-off-by: Daniel P. Berrangé<berrange@redhat.com>
> ---
>   include/qemu/thread.h    |  1 +
>   util/qemu-thread-posix.c | 30 ++++++++++++++++++------------
>   util/qemu-thread-win32.c |  6 +++---
>   3 files changed, 22 insertions(+), 15 deletions(-)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

r~

Re: [PATCH v2 05/14] audio: make jackaudio use qemu_thread_set_name

[Richard Henderson]

On 8/30/25 04:03, Daniel P. Berrangé wrote:
> This has greater portability than directly call pthread_setname_np,
> which is only 1 out of 3 possible functions for pthreads that can
> set the name.
> 
> The new API requires a trampoline function, since it can only set
> the name of the current thread.
> 
> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
> ---
>   audio/jackaudio.c | 28 +++++++++++++++++++++++-----
>   1 file changed, 23 insertions(+), 5 deletions(-)
> 
> diff --git a/audio/jackaudio.c b/audio/jackaudio.c
> index 974a3caad3..48ffbf735f 100644
> --- a/audio/jackaudio.c
> +++ b/audio/jackaudio.c
> @@ -629,18 +629,36 @@ static void qjack_enable_in(HWVoiceIn *hw, bool enable)
>       ji->c.enabled = enable;
>   }
>   
> -#if !defined(WIN32) && defined(CONFIG_PTHREAD_SETNAME_NP_W_TID)
> +#if !defined(WIN32)
> +struct QJackThreadData {
> +    void *(*function)(void *);
> +    void *arg;
> +};
> +
> +static void *qjack_thread_trampoline(void *targ)
> +{
> +    struct QJackThreadData *data = targ;
> +    void *(*function)(void *) = data->function;
> +    void *arg = data->arg;
> +
> +    g_free(data);
> +    qemu_thread_set_name("jack-client");
> +
> +    return function(arg);
> +}
> +
>   static int qjack_thread_creator(jack_native_thread_t *thread,
>       const pthread_attr_t *attr, void *(*function)(void *), void *arg)
>   {
> -    int ret = pthread_create(thread, attr, function, arg);
> +    struct QJackThreadData *data = g_new0(struct QJackThreadData, 1);
> +    data->function = function;
> +    data->arg = arg;
> +    int ret = pthread_create(thread, attr, qjack_thread_trampoline, data);
>       if (ret != 0) {
> +        g_free(data);
>           return ret;
>       }
>   
> -    /* set the name of the thread */
> -    pthread_setname_np(*thread, "jack-client");
> -

You need to make jack_set_thread_creator later on unconditional as well.


r~

Re: [PATCH v2 06/14] util: set the name for the 'main' thread

[Richard Henderson]

On 8/30/25 04:03, Daniel P. Berrangé wrote:
> The default main thread name is undefined, so use a constructor to
> explicitly set it to 'main'. This constructor is marked to run early
> as the thread name is intended to be used in error reporting / logs
> which may be triggered very early in QEMU execution.
> 
> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
> ---
>   util/qemu-thread-posix.c | 6 ++++++
>   util/qemu-thread-win32.c | 6 ++++++
>   2 files changed, 12 insertions(+)
> 
> diff --git a/util/qemu-thread-posix.c b/util/qemu-thread-posix.c
> index ddaa1de4dd..275445ed94 100644
> --- a/util/qemu-thread-posix.c
> +++ b/util/qemu-thread-posix.c
> @@ -22,6 +22,12 @@
>   #include <pthread_np.h>
>   #endif
>   
> +static void __attribute__((__constructor__(QEMU_CONSTRUCTOR_EARLY)))
> +qemu_thread_init(void)
> +{
> +    qemu_thread_set_name("main");
> +}
> +
>   static void error_exit(int err, const char *msg)
>   {
>       fprintf(stderr, "qemu: %s: %s\n", msg, strerror(err));
> diff --git a/util/qemu-thread-win32.c b/util/qemu-thread-win32.c
> index 62eaa11026..7a734a7a09 100644
> --- a/util/qemu-thread-win32.c
> +++ b/util/qemu-thread-win32.c
> @@ -22,6 +22,12 @@ typedef HRESULT (WINAPI *pSetThreadDescription) (HANDLE hThread,
>   static pSetThreadDescription SetThreadDescriptionFunc;
>   static HMODULE kernel32_module;
>   
> +static void __attribute__((__constructor__(QEMU_CONSTRUCTOR_EARLY)))
> +qemu_thread_init(void)
> +{
> +    qemu_thread_set_name("main");
> +}
> +
>   static bool load_set_thread_description(void)
>   {
>       static gsize _init_once = 0;

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

r~

Re: [PATCH v2 07/14] util: add API to fetch the current thread name

[Richard Henderson]

On 8/30/25 04:03, Daniel P. Berrangé wrote:
> +#ifndef PTHREAD_MAX_NAMELEN_NP
> +#define PTHREAD_MAX_NAMELEN_NP 16
> +#endif
> +
> +static __thread char namebuf[PTHREAD_MAX_NAMELEN_NP];

If you're going to have this...

> +static __thread char namebuf[64];

... or this, why not just remember the name from when we set it?

You could even store a pointer instead of a larger number of characters.  I'll note that 
all of the names we actually pass to qemu_thread_create are string literals, and that we 
don't actually need to do any memory allocation at all with them.


> +    name = g_utf16_to_utf8(namew, -1, NULL, NULL, NULL);
> +    LocalFree(namew);
> +    if (!name) {
> +        goto error;
> +    }

That would certainly avoid this kind of hassle.

Re: [PATCH v2 01/14] include: define constant for early constructor priority

[Dr. David Alan Gilbert]

* Daniel P. Berrangé (berrange@redhat.com) wrote:
> Functions marked with __attribute__((__constructor__)) will be
> invoked in linker order. In theory this is well defined, but
> in practice, it is hard to determine what this order will be
> with the layers of indirection through meson, ninja and the
> static libraries QEMU builds.
> 
> Notably, the order currently appears different between Linux
> and Windows (as tested with Wine on Linux). This can cause
> problems when certain QEMU constructors have a dependancy on
> other QEMU constructors.
> 
> To address this define a QEMU_CONSTRUCTOR_EARLY constant which
> provides a priority value that will run before other default
> constructors. This is to be used for QEMU constructors that
> are themselves self-contained, but may be relied upon by other
> constructors.
> 
> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

Reviewed-by: Dr. David Alan Gilbert <dave@treblig.org>

> ---
>  include/qemu/compiler.h | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/include/qemu/compiler.h b/include/qemu/compiler.h
> index 1c2b673c05..4c49f52eb0 100644
> --- a/include/qemu/compiler.h
> +++ b/include/qemu/compiler.h
> @@ -194,6 +194,14 @@
>  # define QEMU_USED
>  #endif
>  
> +/*
> + * A priority for __attribute__((constructor(...))) that
> + * will run earlier than the default constructors. Must
> + * only be used for functions that have no dependency
> + * on global initialization of other QEMU subsystems.
> + */
> +#define QEMU_CONSTRUCTOR_EARLY 101
> +
>  /*
>   * Disable -ftrivial-auto-var-init on a local variable.
>   *
> -- 
> 2.50.1
> 
-- 
 -----Open up your eyes, open up your mind, open up your code -------   
/ Dr. David Alan Gilbert    |       Running GNU/Linux       | Happy  \ 
\        dave @ treblig.org |                               | In Hex /
 \ _________________________|_____ http://www.treblig.org   |_______/

Re: [PATCH v2 02/14] monitor: initialize global data from a constructor

[Dr. David Alan Gilbert]

* Daniel P. Berrangé (berrange@redhat.com) wrote:
> Some monitor functions, most notably, monitor_cur() rely on global
> data being initialized by 'monitor_init_globals()'. The latter is
> called relatively late in startup. If code triggers error_report()
> before monitor_init_globals() is called, QEMU will abort when
> accessing the uninitialized monitor mutex.
> 
> The critical monitor global data must be initialized from a
> constructor function, to improve the guarantee that it is done
> before any possible calls to monitor_cur(). Not only that, but
> the constructor must be marked to run before the default
> constructor in case any of them trigger error reporting.
> 
> Note in particular that the RCU constructor will spawn a background
> thread so we might even have non-constructor QEMU code running
> concurrently with other constructors.
> 
> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

Checked that qemu_mutex_init doesn't look like it can call
error code; so

Reviewed-by: Dr. David Alan Gilbert <dave@treblig.org>

> ---
>  monitor/monitor.c | 14 +++++++++-----
>  1 file changed, 9 insertions(+), 5 deletions(-)
> 
> diff --git a/monitor/monitor.c b/monitor/monitor.c
> index c5a5d30877..da54e1b1ce 100644
> --- a/monitor/monitor.c
> +++ b/monitor/monitor.c
> @@ -704,18 +704,22 @@ void monitor_cleanup(void)
>      }
>  }
>  
> -static void monitor_qapi_event_init(void)
> +/*
> + * Initialize static vars that have no deps on external
> + * module initialization, and are required for external
> + * functions to call things like monitor_cur()
> + */
> +static void __attribute__((__constructor__(QEMU_CONSTRUCTOR_EARLY)))
> +monitor_init_static(void)
>  {
> +    qemu_mutex_init(&monitor_lock);
> +    coroutine_mon = g_hash_table_new(NULL, NULL);
>      monitor_qapi_event_state = g_hash_table_new(qapi_event_throttle_hash,
>                                                  qapi_event_throttle_equal);
>  }
>  
>  void monitor_init_globals(void)
>  {
> -    monitor_qapi_event_init();
> -    qemu_mutex_init(&monitor_lock);
> -    coroutine_mon = g_hash_table_new(NULL, NULL);
> -
>      /*
>       * The dispatcher BH must run in the main loop thread, since we
>       * have commands assuming that context.  It would be nice to get
> -- 
> 2.50.1
> 
-- 
 -----Open up your eyes, open up your mind, open up your code -------   
/ Dr. David Alan Gilbert    |       Running GNU/Linux       | Happy  \ 
\        dave @ treblig.org |                               | In Hex /
 \ _________________________|_____ http://www.treblig.org   |_______/

Re: [PATCH v2 04/14] util: expose qemu_thread_set_name

[Dr. David Alan Gilbert]

* Daniel P. Berrangé (berrange@redhat.com) wrote:
> The ability to set the thread name needs to be used in a number
> of places, so expose the current impls as public methods.
> 
> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

Reviewed-by: Dr. David Alan Gilbert <dave@treblig.org>

> ---
>  include/qemu/thread.h    |  1 +
>  util/qemu-thread-posix.c | 30 ++++++++++++++++++------------
>  util/qemu-thread-win32.c |  6 +++---
>  3 files changed, 22 insertions(+), 15 deletions(-)
> 
> diff --git a/include/qemu/thread.h b/include/qemu/thread.h
> index 3a286bb3ef..27b888ab0a 100644
> --- a/include/qemu/thread.h
> +++ b/include/qemu/thread.h
> @@ -215,6 +215,7 @@ void *qemu_thread_join(QemuThread *thread);
>  void qemu_thread_get_self(QemuThread *thread);
>  bool qemu_thread_is_self(QemuThread *thread);
>  G_NORETURN void qemu_thread_exit(void *retval);
> +void qemu_thread_set_name(const char *name);
>  
>  struct Notifier;
>  /**
> diff --git a/util/qemu-thread-posix.c b/util/qemu-thread-posix.c
> index 7c985b5d38..ddaa1de4dd 100644
> --- a/util/qemu-thread-posix.c
> +++ b/util/qemu-thread-posix.c
> @@ -329,6 +329,21 @@ static void qemu_thread_atexit_notify(void *arg)
>      notifier_list_notify(&thread_exit, NULL);
>  }
>  
> +void qemu_thread_set_name(const char *name)
> +{
> +    /*
> +     * Attempt to set the threads name; note that this is for debug, so
> +     * we're not going to fail if we can't set it.
> +     */
> +# if defined(CONFIG_PTHREAD_SETNAME_NP_W_TID)
> +    pthread_setname_np(pthread_self(), name);
> +# elif defined(CONFIG_PTHREAD_SETNAME_NP_WO_TID)
> +    pthread_setname_np(name);
> +# elif defined(CONFIG_PTHREAD_SET_NAME_NP)
> +    pthread_set_name_np(pthread_self(), name);
> +# endif
> +}
> +
>  typedef struct {
>      void *(*start_routine)(void *);
>      void *arg;
> @@ -342,20 +357,11 @@ static void *qemu_thread_start(void *args)
>      void *arg = qemu_thread_args->arg;
>      void *r;
>  
> -    /* Attempt to set the threads name; note that this is for debug, so
> -     * we're not going to fail if we can't set it.
> -     */
>      if (qemu_thread_args->name) {
> -# if defined(CONFIG_PTHREAD_SETNAME_NP_W_TID)
> -        pthread_setname_np(pthread_self(), qemu_thread_args->name);
> -# elif defined(CONFIG_PTHREAD_SETNAME_NP_WO_TID)
> -        pthread_setname_np(qemu_thread_args->name);
> -# elif defined(CONFIG_PTHREAD_SET_NAME_NP)
> -        pthread_set_name_np(pthread_self(), qemu_thread_args->name);
> -# endif
> +        qemu_thread_set_name(qemu_thread_args->name);
> +        QEMU_TSAN_ANNOTATE_THREAD_NAME(qemu_thread_args->name);
> +        g_free(qemu_thread_args->name);
>      }
> -    QEMU_TSAN_ANNOTATE_THREAD_NAME(qemu_thread_args->name);
> -    g_free(qemu_thread_args->name);
>      g_free(qemu_thread_args);
>  
>      /*
> diff --git a/util/qemu-thread-win32.c b/util/qemu-thread-win32.c
> index 9595a5b090..62eaa11026 100644
> --- a/util/qemu-thread-win32.c
> +++ b/util/qemu-thread-win32.c
> @@ -316,7 +316,7 @@ void *qemu_thread_join(QemuThread *thread)
>      return ret;
>  }
>  
> -static void set_thread_description(HANDLE h, const char *name)
> +void qemu_thread_set_name(const char *name)
>  {
>      g_autofree wchar_t *namew = NULL;
>  
> @@ -329,7 +329,7 @@ static void set_thread_description(HANDLE h, const char *name)
>          return;
>      }
>  
> -    SetThreadDescriptionFunc(h, namew);
> +    SetThreadDescriptionFunc(GetCurrentThread(), namew);
>  }
>  
>  void qemu_thread_create(QemuThread *thread, const char *name,
> @@ -356,7 +356,7 @@ void qemu_thread_create(QemuThread *thread, const char *name,
>          error_exit(GetLastError(), __func__);
>      }
>      if (name) {
> -        set_thread_description(hThread, name);
> +        qemu_thread_set_name(name);
>      }
>      CloseHandle(hThread);
>  
> -- 
> 2.50.1
> 
-- 
 -----Open up your eyes, open up your mind, open up your code -------   
/ Dr. David Alan Gilbert    |       Running GNU/Linux       | Happy  \ 
\        dave @ treblig.org |                               | In Hex /
 \ _________________________|_____ http://www.treblig.org   |_______/

Re: [PATCH v2 05/14] audio: make jackaudio use qemu_thread_set_name

[Dr. David Alan Gilbert]

* Daniel P. Berrangé (berrange@redhat.com) wrote:
> This has greater portability than directly call pthread_setname_np,
> which is only 1 out of 3 possible functions for pthreads that can
> set the name.
> 
> The new API requires a trampoline function, since it can only set
> the name of the current thread.
> 
> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

Reviewed-by: Dr. David Alan Gilbert <dave@treblig.org>

> ---
>  audio/jackaudio.c | 28 +++++++++++++++++++++++-----
>  1 file changed, 23 insertions(+), 5 deletions(-)
> 
> diff --git a/audio/jackaudio.c b/audio/jackaudio.c
> index 974a3caad3..48ffbf735f 100644
> --- a/audio/jackaudio.c
> +++ b/audio/jackaudio.c
> @@ -629,18 +629,36 @@ static void qjack_enable_in(HWVoiceIn *hw, bool enable)
>      ji->c.enabled = enable;
>  }
>  
> -#if !defined(WIN32) && defined(CONFIG_PTHREAD_SETNAME_NP_W_TID)
> +#if !defined(WIN32)
> +struct QJackThreadData {
> +    void *(*function)(void *);
> +    void *arg;
> +};
> +
> +static void *qjack_thread_trampoline(void *targ)
> +{
> +    struct QJackThreadData *data = targ;
> +    void *(*function)(void *) = data->function;
> +    void *arg = data->arg;
> +
> +    g_free(data);
> +    qemu_thread_set_name("jack-client");
> +
> +    return function(arg);
> +}
> +
>  static int qjack_thread_creator(jack_native_thread_t *thread,
>      const pthread_attr_t *attr, void *(*function)(void *), void *arg)
>  {
> -    int ret = pthread_create(thread, attr, function, arg);
> +    struct QJackThreadData *data = g_new0(struct QJackThreadData, 1);
> +    data->function = function;
> +    data->arg = arg;
> +    int ret = pthread_create(thread, attr, qjack_thread_trampoline, data);
>      if (ret != 0) {
> +        g_free(data);
>          return ret;
>      }
>  
> -    /* set the name of the thread */
> -    pthread_setname_np(*thread, "jack-client");
> -
>      return ret;
>  }
>  #endif
> -- 
> 2.50.1
> 
-- 
 -----Open up your eyes, open up your mind, open up your code -------   
/ Dr. David Alan Gilbert    |       Running GNU/Linux       | Happy  \ 
\        dave @ treblig.org |                               | In Hex /
 \ _________________________|_____ http://www.treblig.org   |_______/

Re: [PATCH v2 06/14] util: set the name for the 'main' thread

[Dr. David Alan Gilbert]

* Daniel P. Berrangé (berrange@redhat.com) wrote:
> The default main thread name is undefined, so use a constructor to
> explicitly set it to 'main'. This constructor is marked to run early
> as the thread name is intended to be used in error reporting / logs
> which may be triggered very early in QEMU execution.
> 
> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

Initially I was unsure why it was in qemu-thread-* - given these
are identical between the posix/windows versions; but I'm not sure
where else it would go.  You'd probably want it in both system and user,
and probably the none-emulator binaries as well.
So this may be the best place.

I'd probably rename it though, it looks like an operation on
a qemu_thread;  like qemu_thread_create() and qemu_thread_start()

Other than that;


Reviewed-by: Dr. David Alan Gilbert <dave@treblig.org>

> ---
>  util/qemu-thread-posix.c | 6 ++++++
>  util/qemu-thread-win32.c | 6 ++++++
>  2 files changed, 12 insertions(+)
> 
> diff --git a/util/qemu-thread-posix.c b/util/qemu-thread-posix.c
> index ddaa1de4dd..275445ed94 100644
> --- a/util/qemu-thread-posix.c
> +++ b/util/qemu-thread-posix.c
> @@ -22,6 +22,12 @@
>  #include <pthread_np.h>
>  #endif
>  
> +static void __attribute__((__constructor__(QEMU_CONSTRUCTOR_EARLY)))
> +qemu_thread_init(void)
> +{
> +    qemu_thread_set_name("main");
> +}
> +
>  static void error_exit(int err, const char *msg)
>  {
>      fprintf(stderr, "qemu: %s: %s\n", msg, strerror(err));
> diff --git a/util/qemu-thread-win32.c b/util/qemu-thread-win32.c
> index 62eaa11026..7a734a7a09 100644
> --- a/util/qemu-thread-win32.c
> +++ b/util/qemu-thread-win32.c
> @@ -22,6 +22,12 @@ typedef HRESULT (WINAPI *pSetThreadDescription) (HANDLE hThread,
>  static pSetThreadDescription SetThreadDescriptionFunc;
>  static HMODULE kernel32_module;
>  
> +static void __attribute__((__constructor__(QEMU_CONSTRUCTOR_EARLY)))
> +qemu_thread_init(void)
> +{
> +    qemu_thread_set_name("main");
> +}
> +
>  static bool load_set_thread_description(void)
>  {
>      static gsize _init_once = 0;
> -- 
> 2.50.1
> 
-- 
 -----Open up your eyes, open up your mind, open up your code -------   
/ Dr. David Alan Gilbert    |       Running GNU/Linux       | Happy  \ 
\        dave @ treblig.org |                               | In Hex /
 \ _________________________|_____ http://www.treblig.org   |_______/

Re: [PATCH v2 07/14] util: add API to fetch the current thread name

[Daniel P. Berrangé]

On Sun, Aug 31, 2025 at 08:14:21AM +1000, Richard Henderson wrote:
> On 8/30/25 04:03, Daniel P. Berrangé wrote:
> > +#ifndef PTHREAD_MAX_NAMELEN_NP
> > +#define PTHREAD_MAX_NAMELEN_NP 16
> > +#endif
> > +
> > +static __thread char namebuf[PTHREAD_MAX_NAMELEN_NP];
> 
> If you're going to have this...
> 
> > +static __thread char namebuf[64];
> 
> ... or this, why not just remember the name from when we set it?
> 
> You could even store a pointer instead of a larger number of characters.
> I'll note that all of the names we actually pass to qemu_thread_create are
> string literals, and that we don't actually need to do any memory allocation
> at all with them.

I was thinking about the possibility there will be threads running that
were not created using qemu_thread_start, given that libraries use threads
behind the scenes and I can't rule out possibility that such threads call
back into QEMU code.

> 
> 
> > +    name = g_utf16_to_utf8(namew, -1, NULL, NULL, NULL);
> > +    LocalFree(namew);
> > +    if (!name) {
> > +        goto error;
> > +    }
> 
> That would certainly avoid this kind of hassle.
> 
> 
> 

With regards,
Daniel
-- 
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|: https://libvirt.org         -o-            https://fstop138.berrange.com :|
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Re: [PATCH v2 07/14] util: add API to fetch the current thread name

[Richard Henderson]

On 9/1/25 18:49, Daniel P. Berrangé wrote:
> On Sun, Aug 31, 2025 at 08:14:21AM +1000, Richard Henderson wrote:
>> On 8/30/25 04:03, Daniel P. Berrangé wrote:
>>> +#ifndef PTHREAD_MAX_NAMELEN_NP
>>> +#define PTHREAD_MAX_NAMELEN_NP 16
>>> +#endif
>>> +
>>> +static __thread char namebuf[PTHREAD_MAX_NAMELEN_NP];
>>
>> If you're going to have this...
>>
>>> +static __thread char namebuf[64];
>>
>> ... or this, why not just remember the name from when we set it?
>>
>> You could even store a pointer instead of a larger number of characters.
>> I'll note that all of the names we actually pass to qemu_thread_create are
>> string literals, and that we don't actually need to do any memory allocation
>> at all with them.
> 
> I was thinking about the possibility there will be threads running that
> were not created using qemu_thread_start, given that libraries use threads
> behind the scenes and I can't rule out possibility that such threads call
> back into QEMU code.

Good point.


r~

Re: [PATCH v2 09/14] util: introduce common helper for error-report & log code

[Richard Henderson]

On 8/29/25 04:03, Daniel P. Berrangé wrote:
> +enum QMessageContextFlags {
> +    QMESSAGE_CONTEXT_SKIP_MONITOR = (1 << 0),
> +};
> +
> +/*
> + * qmessage_context:
> + * @flags: the message formatting control flags
> + *
> + * Format a message prefix with the information
> + * previously selected by a call to
> + * qmessage_set_format.
> + *
> + * If @flags contains QMESSAGE_CONTEXT_SKIP_MONITOR
> + * an empty string will be returned if running in
> + * the context of a HMP command
> + *
> + * Returns: a formatted message prefix, or empty string;
> + * to be freed by the caller.
> + */
> +char *qmessage_context(int flags);

I don't like QMESSAGE_CONTEXT_SKIP_MONITOR.
It's just as easy to check monitor_cur in the single user and not call qmessage_context.

The comment is out-of-date, since you can now return NULL.
That said, I have a follow-up suggestion.


r~