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-rw-r--r--async.c33
-rw-r--r--include/block/aio.h7
2 files changed, 38 insertions, 2 deletions
diff --git a/async.c b/async.c
index 90fe906539..5ce3633010 100644
--- a/async.c
+++ b/async.c
@@ -47,11 +47,16 @@ QEMUBH *aio_bh_new(AioContext *ctx, QEMUBHFunc *cb, void *opaque)
bh->ctx = ctx;
bh->cb = cb;
bh->opaque = opaque;
+ qemu_mutex_lock(&ctx->bh_lock);
bh->next = ctx->first_bh;
+ /* Make sure that the members are ready before putting bh into list */
+ smp_wmb();
ctx->first_bh = bh;
+ qemu_mutex_unlock(&ctx->bh_lock);
return bh;
}
+/* Multiple occurrences of aio_bh_poll cannot be called concurrently */
int aio_bh_poll(AioContext *ctx)
{
QEMUBH *bh, **bhp, *next;
@@ -61,9 +66,15 @@ int aio_bh_poll(AioContext *ctx)
ret = 0;
for (bh = ctx->first_bh; bh; bh = next) {
+ /* Make sure that fetching bh happens before accessing its members */
+ smp_read_barrier_depends();
next = bh->next;
if (!bh->deleted && bh->scheduled) {
bh->scheduled = 0;
+ /* Paired with write barrier in bh schedule to ensure reading for
+ * idle & callbacks coming after bh's scheduling.
+ */
+ smp_rmb();
if (!bh->idle)
ret = 1;
bh->idle = 0;
@@ -75,6 +86,7 @@ int aio_bh_poll(AioContext *ctx)
/* remove deleted bhs */
if (!ctx->walking_bh) {
+ qemu_mutex_lock(&ctx->bh_lock);
bhp = &ctx->first_bh;
while (*bhp) {
bh = *bhp;
@@ -85,6 +97,7 @@ int aio_bh_poll(AioContext *ctx)
bhp = &bh->next;
}
}
+ qemu_mutex_unlock(&ctx->bh_lock);
}
return ret;
@@ -94,24 +107,38 @@ void qemu_bh_schedule_idle(QEMUBH *bh)
{
if (bh->scheduled)
return;
- bh->scheduled = 1;
bh->idle = 1;
+ /* Make sure that idle & any writes needed by the callback are done
+ * before the locations are read in the aio_bh_poll.
+ */
+ smp_wmb();
+ bh->scheduled = 1;
}
void qemu_bh_schedule(QEMUBH *bh)
{
if (bh->scheduled)
return;
- bh->scheduled = 1;
bh->idle = 0;
+ /* Make sure that idle & any writes needed by the callback are done
+ * before the locations are read in the aio_bh_poll.
+ */
+ smp_wmb();
+ bh->scheduled = 1;
aio_notify(bh->ctx);
}
+
+/* This func is async.
+ */
void qemu_bh_cancel(QEMUBH *bh)
{
bh->scheduled = 0;
}
+/* This func is async.The bottom half will do the delete action at the finial
+ * end.
+ */
void qemu_bh_delete(QEMUBH *bh)
{
bh->scheduled = 0;
@@ -176,6 +203,7 @@ aio_ctx_finalize(GSource *source)
thread_pool_free(ctx->thread_pool);
aio_set_event_notifier(ctx, &ctx->notifier, NULL, NULL);
event_notifier_cleanup(&ctx->notifier);
+ qemu_mutex_destroy(&ctx->bh_lock);
g_array_free(ctx->pollfds, TRUE);
}
@@ -211,6 +239,7 @@ AioContext *aio_context_new(void)
ctx = (AioContext *) g_source_new(&aio_source_funcs, sizeof(AioContext));
ctx->pollfds = g_array_new(FALSE, FALSE, sizeof(GPollFD));
ctx->thread_pool = NULL;
+ qemu_mutex_init(&ctx->bh_lock);
event_notifier_init(&ctx->notifier, false);
aio_set_event_notifier(ctx, &ctx->notifier,
(EventNotifierHandler *)
diff --git a/include/block/aio.h b/include/block/aio.h
index 183679374f..cc77771c46 100644
--- a/include/block/aio.h
+++ b/include/block/aio.h
@@ -17,6 +17,7 @@
#include "qemu-common.h"
#include "qemu/queue.h"
#include "qemu/event_notifier.h"
+#include "qemu/thread.h"
typedef struct BlockDriverAIOCB BlockDriverAIOCB;
typedef void BlockDriverCompletionFunc(void *opaque, int ret);
@@ -53,6 +54,8 @@ typedef struct AioContext {
*/
int walking_handlers;
+ /* lock to protect between bh's adders and deleter */
+ QemuMutex bh_lock;
/* Anchor of the list of Bottom Halves belonging to the context */
struct QEMUBH *first_bh;
@@ -127,6 +130,8 @@ void aio_notify(AioContext *ctx);
* aio_bh_poll: Poll bottom halves for an AioContext.
*
* These are internal functions used by the QEMU main loop.
+ * And notice that multiple occurrences of aio_bh_poll cannot
+ * be called concurrently
*/
int aio_bh_poll(AioContext *ctx);
@@ -163,6 +168,8 @@ void qemu_bh_cancel(QEMUBH *bh);
* Deleting a bottom half frees the memory that was allocated for it by
* qemu_bh_new. It also implies canceling the bottom half if it was
* scheduled.
+ * This func is async. The bottom half will do the delete action at the finial
+ * end.
*
* @bh: The bottom half to be deleted.
*/