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 <jos...@linux.vnet.ibm.com>
---
v2:
- removed unecessary (void*) cast
- renamed parameter name to lock instead of qemu_global_mutex
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..4f77d7b 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(&mutex->lock);
}
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(&mutex->lock);
}
void qemu_rec_mutex_init(QemuRecMutex *mutex)
diff --git a/util/trace-events b/util/trace-events
index b44ef4f..70f6212 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 *lock) "locked mutex %p"
+qemu_mutex_unlock(void *lock) "unlocked mutex %p"
--
2.7.4
