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[PULL 35/61] lockable: add lock guards
From: |
Paolo Bonzini |
Subject: |
[PULL 35/61] lockable: add lock guards |
Date: |
Mon, 16 Mar 2020 22:27:02 +0100 |
From: Stefan Hajnoczi <address@hidden>
This patch introduces two lock guard macros that automatically unlock a
lock object (QemuMutex and others):
void f(void) {
QEMU_LOCK_GUARD(&mutex);
if (!may_fail()) {
return; /* automatically unlocks mutex */
}
...
}
and:
WITH_QEMU_LOCK_GUARD(&mutex) {
if (!may_fail()) {
return; /* automatically unlocks mutex */
}
}
/* automatically unlocks mutex here */
...
Convert qemu-timer.c functions that benefit from these macros as an
example. Manual qemu_mutex_lock/unlock() callers are left unmodified in
cases where clarity would not improve by switching to the macros.
Many other QemuMutex users remain in the codebase that might benefit
from lock guards. Over time they can be converted, if that is
desirable.
Signed-off-by: Stefan Hajnoczi <address@hidden>
Signed-off-by: Paolo Bonzini <address@hidden>
---
include/qemu/lockable.h | 65 +++++++++++++++++++++++++++++++++++++++++++++++++
util/qemu-timer.c | 23 +++++++++--------
2 files changed, 76 insertions(+), 12 deletions(-)
diff --git a/include/qemu/lockable.h b/include/qemu/lockable.h
index 84ea794..2b52c7c 100644
--- a/include/qemu/lockable.h
+++ b/include/qemu/lockable.h
@@ -93,4 +93,69 @@ static inline void qemu_lockable_unlock(QemuLockable *x)
x->unlock(x->object);
}
+static inline QemuLockable *qemu_lockable_auto_lock(QemuLockable *x)
+{
+ qemu_lockable_lock(x);
+ return x;
+}
+
+static inline void qemu_lockable_auto_unlock(QemuLockable *x)
+{
+ if (x) {
+ qemu_lockable_unlock(x);
+ }
+}
+
+G_DEFINE_AUTOPTR_CLEANUP_FUNC(QemuLockable, qemu_lockable_auto_unlock)
+
+#define WITH_QEMU_LOCK_GUARD_(x, var) \
+ for (g_autoptr(QemuLockable) var = \
+ qemu_lockable_auto_lock(QEMU_MAKE_LOCKABLE((x))); \
+ var; \
+ qemu_lockable_auto_unlock(var), var = NULL)
+
+/**
+ * WITH_QEMU_LOCK_GUARD - Lock a lock object for scope
+ *
+ * @x: a lock object (currently one of QemuMutex, CoMutex, QemuSpin).
+ *
+ * This macro defines a lock scope such that entering the scope takes the lock
+ * and leaving the scope releases the lock. Return statements are allowed
+ * within the scope and release the lock. Break and continue statements leave
+ * the scope early and release the lock.
+ *
+ * WITH_QEMU_LOCK_GUARD(&mutex) {
+ * ...
+ * if (error) {
+ * return; <-- mutex is automatically unlocked
+ * }
+ *
+ * if (early_exit) {
+ * break; <-- leave this scope early
+ * }
+ * ...
+ * }
+ */
+#define WITH_QEMU_LOCK_GUARD(x) \
+ WITH_QEMU_LOCK_GUARD_((x), qemu_lockable_auto##__COUNTER__)
+
+/**
+ * QEMU_LOCK_GUARD - Lock an object until the end of the scope
+ *
+ * @x: a lock object (currently one of QemuMutex, CoMutex, QemuSpin).
+ *
+ * This macro takes a lock until the end of the scope. Return statements
+ * release the lock.
+ *
+ * ... <-- mutex not locked
+ * QEMU_LOCK_GUARD(&mutex); <-- mutex locked from here onwards
+ * ...
+ * if (error) {
+ * return; <-- mutex is automatically unlocked
+ * }
+ */
+#define QEMU_LOCK_GUARD(x) \
+ g_autoptr(QemuLockable) qemu_lockable_auto##__COUNTER__ = \
+ qemu_lockable_auto_lock(QEMU_MAKE_LOCKABLE((x)))
+
#endif
diff --git a/util/qemu-timer.c b/util/qemu-timer.c
index ef52d28..d548d3c 100644
--- a/util/qemu-timer.c
+++ b/util/qemu-timer.c
@@ -25,6 +25,7 @@
#include "qemu/osdep.h"
#include "qemu/main-loop.h"
#include "qemu/timer.h"
+#include "qemu/lockable.h"
#include "sysemu/replay.h"
#include "sysemu/cpus.h"
@@ -186,13 +187,12 @@ bool timerlist_expired(QEMUTimerList *timer_list)
return false;
}
- qemu_mutex_lock(&timer_list->active_timers_lock);
- if (!timer_list->active_timers) {
- qemu_mutex_unlock(&timer_list->active_timers_lock);
- return false;
+ WITH_QEMU_LOCK_GUARD(&timer_list->active_timers_lock) {
+ if (!timer_list->active_timers) {
+ return false;
+ }
+ expire_time = timer_list->active_timers->expire_time;
}
- expire_time = timer_list->active_timers->expire_time;
- qemu_mutex_unlock(&timer_list->active_timers_lock);
return expire_time <= qemu_clock_get_ns(timer_list->clock->type);
}
@@ -225,13 +225,12 @@ int64_t timerlist_deadline_ns(QEMUTimerList *timer_list)
* value but ->notify_cb() is called when the deadline changes. Therefore
* the caller should notice the change and there is no race condition.
*/
- qemu_mutex_lock(&timer_list->active_timers_lock);
- if (!timer_list->active_timers) {
- qemu_mutex_unlock(&timer_list->active_timers_lock);
- return -1;
+ WITH_QEMU_LOCK_GUARD(&timer_list->active_timers_lock) {
+ if (!timer_list->active_timers) {
+ return -1;
+ }
+ expire_time = timer_list->active_timers->expire_time;
}
- expire_time = timer_list->active_timers->expire_time;
- qemu_mutex_unlock(&timer_list->active_timers_lock);
delta = expire_time - qemu_clock_get_ns(timer_list->clock->type);
--
1.8.3.1
- [PULL 25/61] hw/audio/fmopl: Move ENV_CURVE to .heap to save 32KiB of .bss, (continued)
- [PULL 25/61] hw/audio/fmopl: Move ENV_CURVE to .heap to save 32KiB of .bss, Paolo Bonzini, 2020/03/16
- [PULL 26/61] hw/audio/intel-hda: Use memory region alias to reduce .rodata by 4.34MB, Paolo Bonzini, 2020/03/16
- [PULL 27/61] hw/usb/quirks: Use smaller types to reduce .rodata by 10KiB, Paolo Bonzini, 2020/03/16
- [PULL 28/61] ui/curses: Make control_characters[] array const, Paolo Bonzini, 2020/03/16
- [PULL 32/61] Use -isystem for linux-headers dir, Paolo Bonzini, 2020/03/16
- [PULL 29/61] ui/curses: Move arrays to .heap to save 74KiB of .bss, Paolo Bonzini, 2020/03/16
- [PULL 31/61] softmmu/vl.c: Handle '-cpu help' and '-device help' before 'no default machine', Paolo Bonzini, 2020/03/16
- [PULL 33/61] exec/rom_reset: Free rom data during inmigrate skip, Paolo Bonzini, 2020/03/16
- [PULL 36/61] lockable: add QemuRecMutex support, Paolo Bonzini, 2020/03/16
- [PULL 40/61] scripts/cocci: Patch to replace memory_region_init_{ram, readonly -> rom}, Paolo Bonzini, 2020/03/16
- [PULL 35/61] lockable: add lock guards,
Paolo Bonzini <=
- [PULL 42/61] hw/display: Use memory_region_init_rom() with read-only regions, Paolo Bonzini, 2020/03/16
- [PULL 30/61] qemu-cpu-models.rst: Document -noTSX, mds-no, taa-no, and tsx-ctrl, Paolo Bonzini, 2020/03/16
- [PULL 34/61] cpus: avoid pause_all_vcpus getting stuck due to race, Paolo Bonzini, 2020/03/16
- [PULL 37/61] memory: Correctly return alias region type, Paolo Bonzini, 2020/03/16
- [PULL 38/61] memory: Simplify memory_region_init_rom_nomigrate() to ease review, Paolo Bonzini, 2020/03/16
- [PULL 39/61] scripts/cocci: Rename memory-region-{init-ram -> housekeeping}, Paolo Bonzini, 2020/03/16
- [PULL 41/61] hw/arm: Use memory_region_init_rom() with read-only regions, Paolo Bonzini, 2020/03/16
- [PULL 44/61] hw/net: Use memory_region_init_rom() with read-only regions, Paolo Bonzini, 2020/03/16
- [PULL 45/61] hw/pci-host: Use memory_region_init_rom() with read-only regions, Paolo Bonzini, 2020/03/16
- [PULL 46/61] hw/ppc: Use memory_region_init_rom() with read-only regions, Paolo Bonzini, 2020/03/16