diff options
| -rw-r--r-- | async.c | 33 | ||||
| -rw-r--r-- | include/block/aio.h | 7 |
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. */ |