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authorJose Ricardo Ziviani <joserz@linux.vnet.ibm.com>2017-04-24 14:19:58 -0300
committerPaolo Bonzini <pbonzini@redhat.com>2017-05-05 12:09:59 +0200
commit31f5a726b59bda5580e2f9413867893501dd7d93 (patch)
tree33c91bb25066d13fc9f79aae3ca2379465dcbe51 /util/qemu-thread-win32.c
parentf68826989cd4d1217797251339579c57b3c0934e (diff)
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 <joserz@linux.vnet.ibm.com> Message-Id: <1493054398-26013-1-git-send-email-joserz@linux.vnet.ibm.com> Reviewed-by: Fam Zheng <famz@redhat.com> [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 <pbonzini@redhat.com>
Diffstat (limited to 'util/qemu-thread-win32.c')
-rw-r--r--util/qemu-thread-win32.c11
1 files changed, 10 insertions, 1 deletions
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 <process.h>
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)