Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
---
docs/multiple-iothreads.txt | 5 ++---
include/block/aio.h | 24 +++++++++++-------------
2 files changed, 13 insertions(+), 16 deletions(-)
diff --git a/docs/multiple-iothreads.txt b/docs/multiple-iothreads.txt
index 723cc7e..4197f62 100644
--- a/docs/multiple-iothreads.txt
+++ b/docs/multiple-iothreads.txt
@@ -84,9 +84,8 @@ How to synchronize with an IOThread
AioContext is not thread-safe so some rules must be followed when using file
descriptors, event notifiers, timers, or BHs across threads:
-1. AioContext functions can be called safely from file descriptor, event
-notifier, timer, or BH callbacks invoked by the AioContext. No locking is
-necessary.
+1. AioContext functions can always be called safely. They handle their
+own locking internally.
2. Other threads wishing to access the AioContext must use
aio_context_acquire()/aio_context_release() for mutual exclusion. Once the
diff --git a/include/block/aio.h b/include/block/aio.h
index 3988d28..5d4ca01 100644
--- a/include/block/aio.h
+++ b/include/block/aio.h
@@ -51,18 +51,12 @@ typedef void IOHandler(void *opaque);
struct AioContext {
GSource source;
- /* Protects all fields from multi-threaded access */
+ /* Used by AioContext users to protect from multi-threaded access. */
RFifoLock lock;
- /* The list of registered AIO handlers */
+ /* The list of registered AIO handlers. Protected by ctx->list_lock. */
QLIST_HEAD(, AioHandler) aio_handlers;
- /* This is a simple lock used to protect the aio_handlers list.
- * Specifically, it's used to ensure that no callbacks are removed while
- * we're walking and dispatching callbacks.
- */
- int walking_handlers;
-
/* Used to avoid unnecessary event_notifier_set calls in aio_notify;
* accessed with atomic primitives. If this field is 0, everything
* (file descriptors, bottom halves, timers) will be re-evaluated
@@ -88,9 +82,9 @@ struct AioContext {
*/
uint32_t notify_me;
- /* A lock to protect between bh's adders and deleter, and to ensure
- * that no callbacks are removed while we're walking and dispatching
- * them.
+ /* A lock to protect between QEMUBH and AioHandler adders and deleter,
+ * and to ensure that no callbacks are removed while we're walking and
+ * dispatching them.
*/
QemuLockCnt list_lock;
@@ -112,10 +106,14 @@ struct AioContext {
bool notified;
EventNotifier notifier;
- /* Thread pool for performing work and receiving completion callbacks */
+ /* Thread pool for performing work and receiving completion callbacks.
+ * Has its own locking.
+ */
struct ThreadPool *thread_pool;
- /* TimerLists for calling timers - one per clock type */
+ /* TimerLists for calling timers - one per clock type. Has its own
+ * locking.
+ */
QEMUTimerListGroup tlg;
};
--
2.4.3
