From 31f5a726b59bda5580e2f9413867893501dd7d93 Mon Sep 17 00:00:00 2001 From: Jose Ricardo Ziviani Date: Mon, 24 Apr 2017 14:19:58 -0300 Subject: trace: add qemu mutex lock and unlock trace events 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 me to see the 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 can 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 Message-Id: <1493054398-26013-1-git-send-email-joserz@linux.vnet.ibm.com> Reviewed-by: Fam Zheng [Also handle trylock, cond_wait and win32; trace "unlocked" while still in the critical section, so that "unlocked" always comes before the next "locked" tracepoint. - Paolo] Signed-off-by: Paolo Bonzini --- util/qemu-thread-posix.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-) (limited to 'util/qemu-thread-posix.c') diff --git a/util/qemu-thread-posix.c b/util/qemu-thread-posix.c index 73e3a0edf5..eacd99e497 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; @@ -60,17 +61,30 @@ void qemu_mutex_lock(QemuMutex *mutex) err = pthread_mutex_lock(&mutex->lock); if (err) error_exit(err, __func__); + + trace_qemu_mutex_locked(mutex); } int qemu_mutex_trylock(QemuMutex *mutex) { - return pthread_mutex_trylock(&mutex->lock); + int err; + + err = pthread_mutex_trylock(&mutex->lock); + if (err == 0) { + trace_qemu_mutex_locked(mutex); + return 0; + } + if (err != EBUSY) { + error_exit(err, __func__); + } + return -EBUSY; } void qemu_mutex_unlock(QemuMutex *mutex) { int err; + trace_qemu_mutex_unlocked(mutex); err = pthread_mutex_unlock(&mutex->lock); if (err) error_exit(err, __func__); @@ -130,7 +144,9 @@ void qemu_cond_wait(QemuCond *cond, QemuMutex *mutex) { int err; + trace_qemu_mutex_unlocked(mutex); err = pthread_cond_wait(&cond->cond, &mutex->lock); + trace_qemu_mutex_locked(mutex); if (err) error_exit(err, __func__); } -- cgit 1.4.1