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-win32.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) (limited to 'util/qemu-thread-win32.c') diff --git a/util/qemu-thread-win32.c b/util/qemu-thread-win32.c index 59befd5202..653f29f442 100644 --- a/util/qemu-thread-win32.c +++ b/util/qemu-thread-win32.c @@ -19,6 +19,7 @@ #include "qemu-common.h" #include "qemu/thread.h" #include "qemu/notify.h" +#include "trace.h" #include static bool name_threads; @@ -55,6 +56,7 @@ void qemu_mutex_destroy(QemuMutex *mutex) void qemu_mutex_lock(QemuMutex *mutex) { AcquireSRWLockExclusive(&mutex->lock); + trace_qemu_mutex_locked(mutex); } int qemu_mutex_trylock(QemuMutex *mutex) @@ -62,11 +64,16 @@ int qemu_mutex_trylock(QemuMutex *mutex) int owned; owned = TryAcquireSRWLockExclusive(&mutex->lock); - return !owned; + if (owned) { + trace_qemu_mutex_locked(mutex); + return 0; + } + return -EBUSY; } void qemu_mutex_unlock(QemuMutex *mutex) { + trace_qemu_mutex_unlocked(mutex); ReleaseSRWLockExclusive(&mutex->lock); } @@ -118,7 +125,9 @@ void qemu_cond_broadcast(QemuCond *cond) void qemu_cond_wait(QemuCond *cond, QemuMutex *mutex) { + trace_qemu_mutex_unlocked(mutex); SleepConditionVariableSRW(&cond->var, &mutex->lock, INFINITE, 0); + trace_qemu_mutex_locked(mutex); } void qemu_sem_init(QemuSemaphore *sem, int init) -- cgit v1.2.3-55-g7522