[Qemu-devel] [PULL 0/5] Tracing patches

[Qemu-devel] [PULL 0/5] Tracing patches

[Stefan Hajnoczi]

The latest fixes and updates to QEMU tracing.

Lluís Vilanova (1):
  trace: Update docs to use example events that exist

Stefan Hajnoczi (4):
  trace: allow trace events with string arguments
  MAINTAINERS: add tracing subsystem
  trace: portable simple trace backend using glib
  trace: use binary file open mode in simpletrace

 MAINTAINERS      |    6 ++++
 docs/tracing.txt |   24 ++++++++--------
 trace/simple.c   |   76 ++++++++++++++++++++++++++++++++++-------------------
 3 files changed, 67 insertions(+), 39 deletions(-)

-- 
1.7.5.4

[Qemu-devel] [PATCH 1/5] trace: allow trace events with string arguments

[Stefan Hajnoczi]

String arguments are useful for producing human-readable traces without
post-processing (e.g. stderr backend).  Although the simple backend
cannot handles strings all others can.  Strings should be allowed and
the simple backend can be extended to support them.

Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
---
 docs/tracing.txt |    8 +++-----
 1 files changed, 3 insertions(+), 5 deletions(-)

diff --git a/docs/tracing.txt b/docs/tracing.txt
index d0171aa..2c33a62 100644
--- a/docs/tracing.txt
+++ b/docs/tracing.txt
@@ -70,11 +70,6 @@ Trace events should use types as follows:
    cannot include all user-defined struct declarations and it is therefore
    necessary to use void * for pointers to structs.
 
-   Pointers (including char *) cannot be dereferenced easily (or at all) in
-   some trace backends.  If pointers are used, ensure they are meaningful by
-   themselves and do not assume the data they point to will be traced.  Do
-   not pass in string arguments.
-
  * For everything else, use primitive scalar types (char, int, long) with the
    appropriate signedness.
 
@@ -182,6 +177,9 @@ source tree.  It may not be as powerful as platform-specific or third-party
 trace backends but it is portable.  This is the recommended trace backend
 unless you have specific needs for more advanced backends.
 
+The "simple" backend currently does not capture string arguments, it simply
+records the char* pointer value instead of the string that is pointed to.
+
 ==== Monitor commands ====
 
 * info trace
-- 
1.7.5.4

[Qemu-devel] [PATCH 2/5] MAINTAINERS: add tracing subsystem

[Stefan Hajnoczi]

Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
---
 MAINTAINERS |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/MAINTAINERS b/MAINTAINERS
index 72b2099..7c5ea87 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -459,6 +459,12 @@ S: Maintained
 F: slirp/
 T: git://git.kiszka.org/qemu.git queues/slirp
 
+Tracing
+M: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
+S: Maintained
+F: trace/
+T: git://repo.or.cz/qemu/stefanha.git tracing
+
 Usermode Emulation
 ------------------
 BSD user
-- 
1.7.5.4

[Qemu-devel] [PATCH 3/5] trace: portable simple trace backend using glib

[Stefan Hajnoczi]

Convert the simple trace backend to glib so that it works under Windows.
We cannot use pthread directly but glib provides portable abstractions.
Also use glib atomics instead of newish gcc builtins which may not be
supported on Windows toolchains.

Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
---
 trace/simple.c |   74 ++++++++++++++++++++++++++++++++++++-------------------
 1 files changed, 48 insertions(+), 26 deletions(-)

diff --git a/trace/simple.c b/trace/simple.c
index a609368..885764a 100644
--- a/trace/simple.c
+++ b/trace/simple.c
@@ -12,8 +12,10 @@
 #include <stdint.h>
 #include <stdio.h>
 #include <time.h>
+#ifndef _WIN32
 #include <signal.h>
 #include <pthread.h>
+#endif
 #include "qemu-timer.h"
 #include "trace.h"
 #include "trace/control.h"
@@ -54,9 +56,9 @@ enum {
  * Trace records are written out by a dedicated thread.  The thread waits for
  * records to become available, writes them out, and then waits again.
  */
-static pthread_mutex_t trace_lock = PTHREAD_MUTEX_INITIALIZER;
-static pthread_cond_t trace_available_cond = PTHREAD_COND_INITIALIZER;
-static pthread_cond_t trace_empty_cond = PTHREAD_COND_INITIALIZER;
+static GStaticMutex trace_lock = G_STATIC_MUTEX_INIT;
+static GCond *trace_available_cond;
+static GCond *trace_empty_cond;
 static bool trace_available;
 static bool trace_writeout_enabled;
 
@@ -93,29 +95,30 @@ static bool get_trace_record(unsigned int idx, TraceRecord *record)
  */
 static void flush_trace_file(bool wait)
 {
-    pthread_mutex_lock(&trace_lock);
+    g_static_mutex_lock(&trace_lock);
     trace_available = true;
-    pthread_cond_signal(&trace_available_cond);
+    g_cond_signal(trace_available_cond);
 
     if (wait) {
-        pthread_cond_wait(&trace_empty_cond, &trace_lock);
+        g_cond_wait(trace_empty_cond, g_static_mutex_get_mutex(&trace_lock));
     }
 
-    pthread_mutex_unlock(&trace_lock);
+    g_static_mutex_unlock(&trace_lock);
 }
 
 static void wait_for_trace_records_available(void)
 {
-    pthread_mutex_lock(&trace_lock);
+    g_static_mutex_lock(&trace_lock);
     while (!(trace_available && trace_writeout_enabled)) {
-        pthread_cond_signal(&trace_empty_cond);
-        pthread_cond_wait(&trace_available_cond, &trace_lock);
+        g_cond_signal(trace_empty_cond);
+        g_cond_wait(trace_available_cond,
+                    g_static_mutex_get_mutex(&trace_lock));
     }
     trace_available = false;
-    pthread_mutex_unlock(&trace_lock);
+    g_static_mutex_unlock(&trace_lock);
 }
 
-static void *writeout_thread(void *opaque)
+static gpointer writeout_thread(gpointer opaque)
 {
     TraceRecord record;
     unsigned int writeout_idx = 0;
@@ -159,7 +162,7 @@ static void trace(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3,
 
     timestamp = get_clock();
 
-    idx = __sync_fetch_and_add(&trace_idx, 1) % TRACE_BUF_LEN;
+    idx = g_atomic_int_exchange_and_add((gint *)&trace_idx, 1) % TRACE_BUF_LEN;
     trace_buf[idx] = (TraceRecord){
         .event = event,
         .timestamp_ns = timestamp,
@@ -331,28 +334,47 @@ bool trace_event_set_state(const char *name, bool state)
     return false;
 }
 
-bool trace_backend_init(const char *events, const char *file)
+/* Helper function to create a thread with signals blocked.  Use glib's
+ * portable threads since QEMU abstractions cannot be used due to reentrancy in
+ * the tracer.  Also note the signal masking on POSIX hosts so that the thread
+ * does not steal signals when the rest of the program wants them blocked.
+ */
+static GThread *trace_thread_create(GThreadFunc fn)
 {
-    pthread_t thread;
-    pthread_attr_t attr;
+    GThread *thread;
+#ifndef _WIN32
     sigset_t set, oldset;
-    int ret;
-
-    pthread_attr_init(&attr);
-    pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
 
     sigfillset(&set);
     pthread_sigmask(SIG_SETMASK, &set, &oldset);
-    ret = pthread_create(&thread, &attr, writeout_thread, NULL);
+#endif
+    thread = g_thread_create(writeout_thread, NULL, FALSE, NULL);
+#ifndef _WIN32
     pthread_sigmask(SIG_SETMASK, &oldset, NULL);
+#endif
 
-    if (ret != 0) {
+    return thread;
+}
+
+bool trace_backend_init(const char *events, const char *file)
+{
+    GThread *thread;
+
+    if (!g_thread_supported()) {
+        g_thread_init(NULL);
+    }
+
+    trace_available_cond = g_cond_new();
+    trace_empty_cond = g_cond_new();
+
+    thread = trace_thread_create(writeout_thread);
+    if (!thread) {
         fprintf(stderr, "warning: unable to initialize simple trace backend\n");
-    } else {
-        atexit(st_flush_trace_buffer);
-        trace_backend_init_events(events);
-        st_set_trace_file(file);
+        return false;
     }
 
+    atexit(st_flush_trace_buffer);
+    trace_backend_init_events(events);
+    st_set_trace_file(file);
     return true;
 }
-- 
1.7.5.4

[Qemu-devel] [PATCH 4/5] trace: use binary file open mode in simpletrace

[Stefan Hajnoczi]

For Windows portability the simple trace backend must use the 'b' file
open mode.  This prevents the stdio library from mangling 0x0a/0x0d
newline characters.

Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
---
 trace/simple.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/trace/simple.c b/trace/simple.c
index 885764a..b639dda 100644
--- a/trace/simple.c
+++ b/trace/simple.c
@@ -234,7 +234,7 @@ void st_set_trace_file_enabled(bool enable)
             .x1 = HEADER_VERSION,
         };
 
-        trace_fp = fopen(trace_file_name, "w");
+        trace_fp = fopen(trace_file_name, "wb");
         if (!trace_fp) {
             return;
         }
-- 
1.7.5.4

[Qemu-devel] [PATCH 5/5] trace: Update docs to use example events that exist

[Stefan Hajnoczi]

From: Lluís Vilanova <vilanova@ac.upc.edu>

The events 'qemu_malloc' and 'qemu_free' used in the examples no longer exist,
so use 'qemu_vmalloc' and 'qemu_vfree' instead.

Signed-off-by: Lluís Vilanova <vilanova@ac.upc.edu>
Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
---
 docs/tracing.txt |   16 +++++++++-------
 1 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/docs/tracing.txt b/docs/tracing.txt
index 2c33a62..95ca16c 100644
--- a/docs/tracing.txt
+++ b/docs/tracing.txt
@@ -31,8 +31,8 @@ There is a set of static trace events declared in the "trace-events" source
 file.  Each trace event declaration names the event, its arguments, and the
 format string which can be used for pretty-printing:
 
-    qemu_malloc(size_t size, void *ptr) "size %zu ptr %p"
-    qemu_free(void *ptr) "ptr %p"
+    qemu_vmalloc(size_t size, void *ptr) "size %zu ptr %p"
+    qemu_vfree(void *ptr) "ptr %p"
 
 The "trace-events" file is processed by the "tracetool" script during build to
 generate code for the trace events.  Trace events are invoked directly from
@@ -40,14 +40,16 @@ source code like this:
 
     #include "trace.h"  /* needed for trace event prototype */
     
-    void *qemu_malloc(size_t size)
+    void *qemu_vmalloc(size_t size)
     {
         void *ptr;
-        if (!size && !allow_zero_malloc()) {
-            abort();
+        size_t align = QEMU_VMALLOC_ALIGN;
+     
+        if (size < align) {
+            align = getpagesize();
         }
-        ptr = oom_check(malloc(size ? size : 1));
-        trace_qemu_malloc(size, ptr);  /* <-- trace event */
+        ptr = qemu_memalign(align, size);
+        trace_qemu_vmalloc(size, ptr);
         return ptr;
     }
 
-- 
1.7.5.4

Re: [Qemu-devel] [PULL 0/5] Tracing patches

[Anthony Liguori]

On 09/21/2011 05:36 AM, Stefan Hajnoczi wrote:
> The latest fixes and updates to QEMU tracing.

Pulled.  Thanks.

Regards,

Anthony Liguori

>
> Lluís Vilanova (1):
>    trace: Update docs to use example events that exist
>
> Stefan Hajnoczi (4):
>    trace: allow trace events with string arguments
>    MAINTAINERS: add tracing subsystem
>    trace: portable simple trace backend using glib
>    trace: use binary file open mode in simpletrace
>
>   MAINTAINERS      |    6 ++++
>   docs/tracing.txt |   24 ++++++++--------
>   trace/simple.c   |   76 ++++++++++++++++++++++++++++++++++-------------------
>   3 files changed, 67 insertions(+), 39 deletions(-)
>