From: Remy Noel <remy.n...@blade-group.com>
It is still used for bottom halves though and to avoid concurent
set_fd_handlers (We could probably decorrelate the two, but
set_fd_handlers are quite rare so it probably isn't worth it).
Signed-off-by: Remy Noel <remy.n...@blade-group.com>
---
include/block/aio.h | 4 +++-
util/aio-posix.c | 20 --------------------
util/aio-win32.c | 9 ---------
util/async.c | 7 +++++--
4 files changed, 8 insertions(+), 32 deletions(-)
diff --git a/include/block/aio.h b/include/block/aio.h
index 0ca25dfec6..99c17a22f7 100644
--- a/include/block/aio.h
+++ b/include/block/aio.h
@@ -57,7 +57,9 @@ struct AioContext {
/* Used by AioContext users to protect from multi-threaded access. */
QemuRecMutex lock;
- /* The list of registered AIO handlers. Protected by ctx->list_lock. */
+ /* The list of registered AIO handlers.
+ * RCU-enabled, writes rotected by ctx->list_lock.
+ */
QLIST_HEAD(, AioHandler) aio_handlers;
/* Used to avoid unnecessary event_notifier_set calls in aio_notify;
diff --git a/util/aio-posix.c b/util/aio-posix.c
index 83db3f65f4..46b7c571cc 100644
--- a/util/aio-posix.c
+++ b/util/aio-posix.c
@@ -341,7 +341,6 @@ static void poll_set_started(AioContext *ctx, bool started)
ctx->poll_started = started;
- qemu_lockcnt_inc(&ctx->list_lock);
rcu_read_lock();
QLIST_FOREACH_RCU(node, &ctx->aio_handlers, node) {
IOHandler *fn;
@@ -357,7 +356,6 @@ static void poll_set_started(AioContext *ctx, bool started)
}
}
rcu_read_unlock();
- qemu_lockcnt_dec(&ctx->list_lock);
}
@@ -374,12 +372,6 @@ bool aio_pending(AioContext *ctx)
AioHandler *node;
bool result = false;
- /*
- * We have to walk very carefully in case aio_set_fd_handler is
- * called while we're walking.
- */
- qemu_lockcnt_inc(&ctx->list_lock);
-
rcu_read_lock();
QLIST_FOREACH_RCU(node, &ctx->aio_handlers, node) {
int revents;
@@ -397,7 +389,6 @@ bool aio_pending(AioContext *ctx)
}
}
rcu_read_unlock();
- qemu_lockcnt_dec(&ctx->list_lock);
return result;
}
@@ -438,10 +429,8 @@ static bool aio_dispatch_handlers(AioContext *ctx)
void aio_dispatch(AioContext *ctx)
{
- qemu_lockcnt_inc(&ctx->list_lock);
aio_bh_poll(ctx);
aio_dispatch_handlers(ctx);
- qemu_lockcnt_dec(&ctx->list_lock);
timerlistgroup_run_timers(&ctx->tlg);
}
@@ -524,8 +513,6 @@ static bool run_poll_handlers_once(AioContext *ctx, int64_t
*timeout)
* Note that ctx->notify_me must be non-zero so this function can detect
* aio_notify().
*
- * Note that the caller must have incremented ctx->list_lock.
- *
* Returns: true if progress was made, false otherwise
*/
static bool run_poll_handlers(AioContext *ctx, int64_t max_ns, int64_t
*timeout)
@@ -534,7 +521,6 @@ static bool run_poll_handlers(AioContext *ctx, int64_t
max_ns, int64_t *timeout)
int64_t start_time, elapsed_time;
assert(ctx->notify_me);
- assert(qemu_lockcnt_count(&ctx->list_lock) > 0);
trace_run_poll_handlers_begin(ctx, max_ns, *timeout);
@@ -563,8 +549,6 @@ static bool run_poll_handlers(AioContext *ctx, int64_t
max_ns, int64_t *timeout)
*
* ctx->notify_me must be non-zero so this function can detect aio_notify().
*
- * Note that the caller must have incremented ctx->list_lock.
- *
* Returns: true if progress was made, false otherwise
*/
static bool try_poll_mode(AioContext *ctx, int64_t *timeout)
@@ -609,8 +593,6 @@ bool aio_poll(AioContext *ctx, bool blocking)
atomic_add(&ctx->notify_me, 2);
}
- qemu_lockcnt_inc(&ctx->list_lock);
-
if (ctx->poll_max_ns) {
start = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
}
@@ -713,8 +695,6 @@ bool aio_poll(AioContext *ctx, bool blocking)
progress |= aio_dispatch_handlers(ctx);
}
- qemu_lockcnt_dec(&ctx->list_lock);
-
progress |= timerlistgroup_run_timers(&ctx->tlg);
return progress;
diff --git a/util/aio-win32.c b/util/aio-win32.c
index d7c694e5ac..881bad0c28 100644
--- a/util/aio-win32.c
+++ b/util/aio-win32.c
@@ -176,7 +176,6 @@ bool aio_prepare(AioContext *ctx)
* We have to walk very carefully in case aio_set_fd_handler is
* called while we're walking.
*/
- qemu_lockcnt_inc(&ctx->list_lock);
rcu_read_lock();
/* fill fd sets */
@@ -206,7 +205,6 @@ bool aio_prepare(AioContext *ctx)
}
}
rcu_read_unlock();
- qemu_lockcnt_dec(&ctx->list_lock);
return have_select_revents;
}
@@ -219,7 +217,6 @@ bool aio_pending(AioContext *ctx)
* We have to walk very carefully in case aio_set_fd_handler is
* called while we're walking.
*/
- qemu_lockcnt_inc(&ctx->list_lock);
rcu_read_lock();
QLIST_FOREACH_RCU(node, &ctx->aio_handlers, node) {
if (node->pfd.revents && node->io_notify) {
@@ -238,7 +235,6 @@ bool aio_pending(AioContext *ctx)
}
rcu_read_unlock();
- qemu_lockcnt_dec(&ctx->list_lock);
return result;
}
@@ -296,10 +292,8 @@ static bool aio_dispatch_handlers(AioContext *ctx, HANDLE
event)
void aio_dispatch(AioContext *ctx)
{
- qemu_lockcnt_inc(&ctx->list_lock);
aio_bh_poll(ctx);
aio_dispatch_handlers(ctx, INVALID_HANDLE_VALUE);
- qemu_lockcnt_dec(&ctx->list_lock);
timerlistgroup_run_timers(&ctx->tlg);
}
@@ -324,7 +318,6 @@ bool aio_poll(AioContext *ctx, bool blocking)
atomic_add(&ctx->notify_me, 2);
}
- qemu_lockcnt_inc(&ctx->list_lock);
have_select_revents = aio_prepare(ctx);
/* fill fd sets */
@@ -381,8 +374,6 @@ bool aio_poll(AioContext *ctx, bool blocking)
progress |= aio_dispatch_handlers(ctx, event);
} while (count > 0);
- qemu_lockcnt_dec(&ctx->list_lock);
-
progress |= timerlistgroup_run_timers(&ctx->tlg);
return progress;
}
diff --git a/util/async.c b/util/async.c
index c10642a385..5078deed83 100644
--- a/util/async.c
+++ b/util/async.c
@@ -100,6 +100,8 @@ int aio_bh_poll(AioContext *ctx)
int ret;
bool deleted = false;
+ qemu_lockcnt_inc(&ctx->list_lock);
+
ret = 0;
for (bh = atomic_rcu_read(&ctx->first_bh); bh; bh = next) {
next = atomic_rcu_read(&bh->next);
@@ -124,10 +126,11 @@ int aio_bh_poll(AioContext *ctx)
/* remove deleted bhs */
if (!deleted) {
+ qemu_lockcnt_dec(&ctx->list_lock);
return ret;
}
- if (qemu_lockcnt_dec_if_lock(&ctx->list_lock)) {
+ if (qemu_lockcnt_dec_and_lock(&ctx->list_lock)) {
bhp = &ctx->first_bh;
while (*bhp) {
bh = *bhp;
@@ -138,7 +141,7 @@ int aio_bh_poll(AioContext *ctx)
bhp = &bh->next;
}
}
- qemu_lockcnt_inc_and_unlock(&ctx->list_lock);
+ qemu_lockcnt_unlock(&ctx->list_lock);
}
return ret;
}
--
2.19.1
