From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:55251) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1d2fFa-0006X3-CQ for qemu-devel@nongnu.org; Mon, 24 Apr 2017 10:46:03 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1d2fFX-0007fu-9W for qemu-devel@nongnu.org; Mon, 24 Apr 2017 10:46:02 -0400 Received: from mx1.redhat.com ([209.132.183.28]:53564) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1d2fFW-0007fe-PO for qemu-devel@nongnu.org; Mon, 24 Apr 2017 10:45:59 -0400 Date: Mon, 24 Apr 2017 22:45:52 +0800 From: Fam Zheng Message-ID: <20170424144552.GA6511@lemon.lan> References: <1493044126-21488-1-git-send-email-joserz@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1493044126-21488-1-git-send-email-joserz@linux.vnet.ibm.com> Subject: Re: [Qemu-devel] [PATCH] trace: add qemu mutex lock and unlock trace events List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jose Ricardo Ziviani Cc: qemu-devel@nongnu.org, pbonzini@redhat.com, stefanha@redhat.com On Mon, 04/24 11:28, Jose Ricardo Ziviani wrote: > These trace events were very useful to help me to understand and find a > reordering issue in vfio, for example: > > qemu_mutex_lock locked mutex 0x10905ad8 > vfio_region_write (0001:03:00.0:region1+0xc0, 0x2020c, 4) > qemu_mutex_unlock unlocked mutex 0x10905ad8 > qemu_mutex_lock locked mutex 0x10905ad8 > vfio_region_write (0001:03:00.0:region1+0xc4, 0xa0000, 4) > qemu_mutex_unlock unlocked mutex 0x10905ad8 > > that also helped to see desired result after the fix: > > qemu_mutex_lock locked mutex 0x10905ad8 > vfio_region_write (0001:03:00.0:region1+0xc0, 0x2000c, 4) > vfio_region_write (0001:03:00.0:region1+0xc4, 0xb0000, 4) > qemu_mutex_unlock unlocked mutex 0x10905ad8 > > So it could be a good idea to have these traces implemented. It's worth > mentioning that they should be surgically enabled during the debugging, > otherwise it'd flood the trace logs with lock/unlock messages. > > How to use it: > trace-event qemu_mutex_lock on|off > trace-event qemu_mutex_unlock on|off > or > trace-event qemu_mutex* on|off > > Signed-off-by: Jose Ricardo Ziviani > --- > util/qemu-thread-posix.c | 5 +++++ > util/trace-events | 4 ++++ > 2 files changed, 9 insertions(+) > > diff --git a/util/qemu-thread-posix.c b/util/qemu-thread-posix.c > index 73e3a0e..909c2ac 100644 > --- a/util/qemu-thread-posix.c > +++ b/util/qemu-thread-posix.c > @@ -14,6 +14,7 @@ > #include "qemu/thread.h" > #include "qemu/atomic.h" > #include "qemu/notify.h" > +#include "trace.h" > > static bool name_threads; > > @@ -60,6 +61,8 @@ void qemu_mutex_lock(QemuMutex *mutex) > err = pthread_mutex_lock(&mutex->lock); > if (err) > error_exit(err, __func__); > + > + trace_qemu_mutex_lock((void *)&mutex->lock); You don't need these casts as the parameter type is void * which accepts any pointers. > } > > int qemu_mutex_trylock(QemuMutex *mutex) > @@ -74,6 +77,8 @@ void qemu_mutex_unlock(QemuMutex *mutex) > err = pthread_mutex_unlock(&mutex->lock); > if (err) > error_exit(err, __func__); > + > + trace_qemu_mutex_unlock((void *)&mutex->lock); > } > > void qemu_rec_mutex_init(QemuRecMutex *mutex) > diff --git a/util/trace-events b/util/trace-events > index b44ef4f..65c33fe 100644 > --- a/util/trace-events > +++ b/util/trace-events > @@ -55,3 +55,7 @@ lockcnt_futex_wait_prepare(const void *lockcnt, int expected, int new) "lockcnt > lockcnt_futex_wait(const void *lockcnt, int val) "lockcnt %p waiting on %d" > lockcnt_futex_wait_resume(const void *lockcnt, int new) "lockcnt %p after wait: %d" > lockcnt_futex_wake(const void *lockcnt) "lockcnt %p waking up one waiter" > + > +# util/qemu-thread-posix.c > +qemu_mutex_lock(void *qemu_global_mutex) "locked mutex %p" > +qemu_mutex_unlock(void *qemu_global_mutex) "unlocked mutex %p" Parameter name is slightly misleading, maybe s/qemu_global_mutex/lock/ for both lines? Fam