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[Qemu-devel] [PULL 10/21] trace: add qemu mutex lock and unlock trace ev
From: |
Paolo Bonzini |
Subject: |
[Qemu-devel] [PULL 10/21] trace: add qemu mutex lock and unlock trace events |
Date: |
Fri, 5 May 2017 12:13:26 +0200 |
From: Jose Ricardo Ziviani <address@hidden>
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 <address@hidden>
Message-Id: <address@hidden>
Reviewed-by: Fam Zheng <address@hidden>
[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 <address@hidden>
---
util/qemu-thread-posix.c | 18 +++++++++++++++++-
util/qemu-thread-win32.c | 11 ++++++++++-
util/trace-events | 4 ++++
3 files changed, 31 insertions(+), 2 deletions(-)
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__);
}
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)
diff --git a/util/trace-events b/util/trace-events
index b44ef4f895..fa540c620b 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_locked(void *lock) "locked mutex %p"
+qemu_mutex_unlocked(void *lock) "unlocked mutex %p"
--
2.12.2
- [Qemu-devel] [PULL 00/21] Misc patches for 2017-05-05, Paolo Bonzini, 2017/05/05
- [Qemu-devel] [PULL 02/21] hw/i386: Build-time assertion on pc/q35 reset register being identical., Paolo Bonzini, 2017/05/05
- [Qemu-devel] [PULL 03/21] char: Fix removing wrong GSource that be found by fd_in_tag, Paolo Bonzini, 2017/05/05
- [Qemu-devel] [PULL 05/21] use _Static_assert in QEMU_BUILD_BUG_ON, Paolo Bonzini, 2017/05/05
- [Qemu-devel] [PULL 01/21] hw/i386: Use Rev3 FADT (ACPI 2.0) instead of Rev1 to improve guest OS support., Paolo Bonzini, 2017/05/05
- [Qemu-devel] [PULL 04/21] target/i386: Add GDB XML register description support, Paolo Bonzini, 2017/05/05
- [Qemu-devel] [PULL 06/21] vl: deprecate the "-hdachs" option, Paolo Bonzini, 2017/05/05
- [Qemu-devel] [PULL 07/21] scsi: avoid an off-by-one error in megasas_mmio_write, Paolo Bonzini, 2017/05/05
- [Qemu-devel] [PULL 10/21] trace: add qemu mutex lock and unlock trace events,
Paolo Bonzini <=
- [Qemu-devel] [PULL 11/21] checkpatch: Disallow glib asserts in main code, Paolo Bonzini, 2017/05/05
- [Qemu-devel] [PULL 13/21] dump: Acquire BQL around vm_start() in dump thread, Paolo Bonzini, 2017/05/05
- [Qemu-devel] [PULL 08/21] sgabios: update for "fix wrong video attrs for int 10h, ah==13h", Paolo Bonzini, 2017/05/05
- [Qemu-devel] [PULL 12/21] hax: Fix memory mapping de-duplication logic, Paolo Bonzini, 2017/05/05
- [Qemu-devel] [PULL 09/21] vmw_pvscsi: check message ring page count at initialisation, Paolo Bonzini, 2017/05/05
- [Qemu-devel] [PULL 14/21] Fix the -accel parameter and the documentation for 'hax', Paolo Bonzini, 2017/05/05
- [Qemu-devel] [PULL 15/21] MAINTAINERS: Add "R:" tag for self-appointed reviewers, Paolo Bonzini, 2017/05/05
- [Qemu-devel] [PULL 16/21] get_maintainer: Teach get_maintainer.pl about the new "R:" tag, Paolo Bonzini, 2017/05/05
- [Qemu-devel] [PULL 19/21] get_maintainer: add subsystem to reviewer output, Paolo Bonzini, 2017/05/05
- [Qemu-devel] [PULL 17/21] get_maintainer: it's '--pattern-depth', not '-pattern-depth', Paolo Bonzini, 2017/05/05