[Qemu-devel] [PATCH 0/1] configure time fix for thread naming on old glibc

[Qemu-devel] [PATCH 0/1] configure time fix for thread naming on old glibc

[Dr. David Alan Gilbert (git)]

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

Peter was preferring configure time detection of pthread_setname_np
to guard against my recent breaking of builds on old libc.

I've tested this on:
   Fedora 20 - modern glibc - works as before
   RHEL 5 - glibc 2.5:
     [dgilbert@davidgil-rhel5 try]$ ./bin/qemu-system-x86_64 -nographic -name debug-threads=on
     qemu: thread naming not supported on this host

   and checked a mingw windows cross build builds.

A check on SLES11 is probably worth a try if someone has one to hand.

Dr. David Alan Gilbert (1):
  Detect pthread_setname_np at configure time

 configure                | 28 ++++++++++++++++++++++++++++
 util/qemu-thread-posix.c | 21 ++++++++++++++++++---
 util/qemu-thread-win32.c |  2 ++
 3 files changed, 48 insertions(+), 3 deletions(-)

-- 
1.8.5.3

[Qemu-devel] [PATCH 1/1] Detect pthread_setname_np at configure time

[Dr. David Alan Gilbert (git)]

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

Warn if no way of setting thread name is available.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
---
 configure                | 28 ++++++++++++++++++++++++++++
 util/qemu-thread-posix.c | 21 ++++++++++++++++++---
 util/qemu-thread-win32.c |  2 ++
 3 files changed, 48 insertions(+), 3 deletions(-)

diff --git a/configure b/configure
index 9539979..d349ba2 100755
--- a/configure
+++ b/configure
@@ -2709,6 +2709,24 @@ if test "$mingw32" != yes -a "$pthread" = no; then
       "Make sure to have the pthread libs and headers installed."
 fi
 
+# check for pthread_setname_np
+pthread_setname_np=no
+cat > $TMPC << EOF
+#include <pthread.h>
+
+static void *f(void *p) { return NULL; }
+int main(void)
+{
+    pthread_t thread;
+    pthread_create(&thread, 0, f, 0);
+    pthread_setname_np(thread, "QEMU");
+    return 0;
+}
+EOF
+if compile_prog "" "$pthread_lib" ; then
+  pthread_setname_np=yes
+fi
+
 ##########################################
 # rbd probe
 if test "$rbd" != "no" ; then
@@ -4636,6 +4654,16 @@ if test "$rdma" = "yes" ; then
   echo "CONFIG_RDMA=y" >> $config_host_mak
 fi
 
+# Hold two types of flag:
+#   CONFIG_THREAD_SETNAME_BYTHREAD  - we've got a way of setting the name on
+#                                     a thread we have a handle to
+#   CONFIG_PTHREAD_SETNAME_NP       - A way of doing it on a particular
+#                                     platform
+if test "$pthread_setname_np" = "yes" ; then
+  echo "CONFIG_THREAD_SETNAME_BYTHREAD=y" >> $config_host_mak
+  echo "CONFIG_PTHREAD_SETNAME_NP=y" >> $config_host_mak
+fi
+
 if test "$tcg_interpreter" = "yes"; then
   QEMU_INCLUDES="-I\$(SRC_PATH)/tcg/tci $QEMU_INCLUDES"
 elif test "$ARCH" = "sparc64" ; then
diff --git a/util/qemu-thread-posix.c b/util/qemu-thread-posix.c
index 960d7f5..d05a649 100644
--- a/util/qemu-thread-posix.c
+++ b/util/qemu-thread-posix.c
@@ -32,6 +32,13 @@ static bool name_threads;
 void qemu_thread_naming(bool enable)
 {
     name_threads = enable;
+
+#ifndef CONFIG_THREAD_SETNAME_BYTHREAD
+    /* 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)
@@ -394,6 +401,16 @@ void qemu_event_wait(QemuEvent *ev)
     }
 }
 
+/* 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.
+ */
+static void qemu_thread_set_name(QemuThread *thread, const char *name)
+{
+#ifdef CONFIG_PTHREAD_SETNAME_NP
+    pthread_setname_np(thread->thread, name);
+#endif
+}
+
 void qemu_thread_create(QemuThread *thread, const char *name,
                        void *(*start_routine)(void*),
                        void *arg, int mode)
@@ -420,11 +437,9 @@ void qemu_thread_create(QemuThread *thread, const char *name,
     if (err)
         error_exit(err, __func__);
 
-#if defined(__GLIBC__) && (__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 12))
     if (name_threads) {
-        pthread_setname_np(thread->thread, name);
+        qemu_thread_set_name(thread, name);
     }
-#endif
 
     pthread_sigmask(SIG_SETMASK, &oldset, NULL);
 
diff --git a/util/qemu-thread-win32.c b/util/qemu-thread-win32.c
index b9c957b..c405c9b 100644
--- a/util/qemu-thread-win32.c
+++ b/util/qemu-thread-win32.c
@@ -22,6 +22,8 @@ void qemu_thread_naming(bool enable)
 {
     /* But note we don't actually name them on Windows yet */
     name_threads = enable;
+
+    fprintf(stderr, "qemu: thread naming not supported on this host\n");
 }
 
 static void error_exit(int err, const char *msg)
-- 
1.8.5.3

[Qemu-devel] Ping: [PATCH 0/1] configure time fix for thread naming on old glibc

[Dr. David Alan Gilbert]

* Dr. David Alan Gilbert (git) (dgilbert@redhat.com) wrote:
> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> 
> Peter was preferring configure time detection of pthread_setname_np
> to guard against my recent breaking of builds on old libc.
> 
> I've tested this on:
>    Fedora 20 - modern glibc - works as before
>    RHEL 5 - glibc 2.5:
>      [dgilbert@davidgil-rhel5 try]$ ./bin/qemu-system-x86_64 -nographic -name debug-threads=on
>      qemu: thread naming not supported on this host
> 
>    and checked a mingw windows cross build builds.
> 
> A check on SLES11 is probably worth a try if someone has one to hand.
> 
> Dr. David Alan Gilbert (1):
>   Detect pthread_setname_np at configure time
> 
>  configure                | 28 ++++++++++++++++++++++++++++
>  util/qemu-thread-posix.c | 21 ++++++++++++++++++---
>  util/qemu-thread-win32.c |  2 ++
>  3 files changed, 48 insertions(+), 3 deletions(-)
> 
> -- 
> 1.8.5.3
> 
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK

Re: [Qemu-devel] [PATCH 0/1] configure time fix for thread naming on old glibc

[Michael S. Tsirkin]

On Wed, Mar 12, 2014 at 11:48:17AM +0000, Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> 
> Peter was preferring configure time detection of pthread_setname_np
> to guard against my recent breaking of builds on old libc.
> 
> I've tested this on:
>    Fedora 20 - modern glibc - works as before
>    RHEL 5 - glibc 2.5:
>      [dgilbert@davidgil-rhel5 try]$ ./bin/qemu-system-x86_64 -nographic -name debug-threads=on
>      qemu: thread naming not supported on this host
> 
>    and checked a mingw windows cross build builds.
> 
> A check on SLES11 is probably worth a try if someone has one to hand.


I've applied this for 2.0, thanks!


> Dr. David Alan Gilbert (1):
>   Detect pthread_setname_np at configure time
> 
>  configure                | 28 ++++++++++++++++++++++++++++
>  util/qemu-thread-posix.c | 21 ++++++++++++++++++---
>  util/qemu-thread-win32.c |  2 ++
>  3 files changed, 48 insertions(+), 3 deletions(-)
> 
> -- 
> 1.8.5.3