On a Wednesday in 2021, Tim Wiederhake wrote:
>Locks a virMutex on creation and unlocks it in its destructor.
>
>Typical usage:
>
> void function(virMutex *m)
> {
> vir_g_autoptr(virLockGuard) lock = virLockGuardNew(m);
Since the developer does not need to refer to the 'lock' variable,
wrapping it in a VIR_MUTEX_LOCK macro would be more convenient.
(Even though it would not be usable outside the variable declaration
section, due to our enabled warnings)
Jano
> /* `m` is locked, and released automatically on scope exit */
>
> ...
> while (expression) {
> vir_g_autoptr(virLockGuard) lock2 = virLockGuardNew(...);
> /* similar */
> }
> }
>
>Signed-off-by: Tim Wiederhake <twiederh@redhat.com>
>---
> src/libvirt_private.syms | 3 +++
> src/util/virthread.c | 26 ++++++++++++++++++++++++++
> src/util/virthread.h | 10 ++++++++++
> 3 files changed, 39 insertions(+)
>
>diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
>index fa11ee3df5..d8170a59af 100644
>--- a/src/libvirt_private.syms
>+++ b/src/libvirt_private.syms
>@@ -3367,6 +3367,9 @@ virCondInit;
> virCondSignal;
> virCondWait;
> virCondWaitUntil;
>+virLockGuardFree;
>+virLockGuardNew;
>+virLockGuardUnlock;
> virMutexDestroy;
> virMutexInit;
> virMutexInitRecursive;
>diff --git a/src/util/virthread.c b/src/util/virthread.c
>index e89c1a09fb..a5a948985f 100644
>--- a/src/util/virthread.c
>+++ b/src/util/virthread.c
>@@ -96,6 +96,32 @@ void virMutexUnlock(virMutex *m)
> pthread_mutex_unlock(&m->lock);
> }
>
>+virLockGuard *virLockGuardNew(virMutex *m)
>+{
>+ virLockGuard *l = g_new0(virLockGuard, 1);
>+ l->mutex = m;
>+
>+ virMutexLock(l->mutex);
>+ return l;
>+}
>+
>+void virLockGuardFree(virLockGuard *l)
>+{
>+ if (!l)
>+ return;
>+
>+ virLockGuardUnlock(l);
>+ g_free(l);
>+}
>+
>+void virLockGuardUnlock(virLockGuard *l)
>+{
>+ if (!l)
>+ return;
>+
>+ virMutexUnlock(g_steal_pointer(&l->mutex));
>+}
>+
>
> int virRWLockInit(virRWLock *m)
> {
>diff --git a/src/util/virthread.h b/src/util/virthread.h
>index 55c8263ae6..b394dbd226 100644
>--- a/src/util/virthread.h
>+++ b/src/util/virthread.h
>@@ -31,6 +31,11 @@ struct virMutex {
> pthread_mutex_t lock;
> };
>
>+typedef struct virLockGuard virLockGuard;
>+struct virLockGuard {
>+ virMutex *mutex;
>+};
>+
> typedef struct virRWLock virRWLock;
> struct virRWLock {
> pthread_rwlock_t lock;
>@@ -121,6 +126,11 @@ void virMutexLock(virMutex *m);
> void virMutexUnlock(virMutex *m);
>
>
>+virLockGuard *virLockGuardNew(virMutex *m);
>+void virLockGuardFree(virLockGuard *l);
>+void virLockGuardUnlock(virLockGuard *l);
>+G_DEFINE_AUTOPTR_CLEANUP_FUNC(virLockGuard, virLockGuardFree);
>+
> int virRWLockInit(virRWLock *m) G_GNUC_WARN_UNUSED_RESULT;
> void virRWLockDestroy(virRWLock *m);
>
>--
>2.31.1
>