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author | Paolo Bonzini <pbonzini@redhat.com> | 2017-01-12 19:07:53 +0100 |
---|---|---|
committer | Stefan Hajnoczi <stefanha@redhat.com> | 2017-01-16 13:25:17 +0000 |
commit | d7c99a1282ca2de1c344b8aa91be5364e9c6aa8f (patch) | |
tree | e7ea12e8f68e634eb89b7a4f98c739442f6745b6 /async.c | |
parent | 51dee5e465e1b3454a886792ca3e14b851e8e67d (diff) | |
download | qemu-d7c99a1282ca2de1c344b8aa91be5364e9c6aa8f.zip qemu-d7c99a1282ca2de1c344b8aa91be5364e9c6aa8f.tar.gz qemu-d7c99a1282ca2de1c344b8aa91be5364e9c6aa8f.tar.bz2 |
aio: make ctx->list_lock a QemuLockCnt, subsuming ctx->walking_bh
This will make it possible to walk the list of bottom halves without
holding the AioContext lock---and in turn to call bottom half
handlers without holding the lock.
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Message-id: 20170112180800.21085-4-pbonzini@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Diffstat (limited to 'async.c')
-rw-r--r-- | async.c | 35 |
1 files changed, 16 insertions, 19 deletions
@@ -53,14 +53,14 @@ void aio_bh_schedule_oneshot(AioContext *ctx, QEMUBHFunc *cb, void *opaque) .cb = cb, .opaque = opaque, }; - qemu_mutex_lock(&ctx->list_lock); + qemu_lockcnt_lock(&ctx->list_lock); bh->next = ctx->first_bh; bh->scheduled = 1; bh->deleted = 1; /* Make sure that the members are ready before putting bh into list */ smp_wmb(); ctx->first_bh = bh; - qemu_mutex_unlock(&ctx->list_lock); + qemu_lockcnt_unlock(&ctx->list_lock); aio_notify(ctx); } @@ -73,12 +73,12 @@ QEMUBH *aio_bh_new(AioContext *ctx, QEMUBHFunc *cb, void *opaque) .cb = cb, .opaque = opaque, }; - qemu_mutex_lock(&ctx->list_lock); + qemu_lockcnt_lock(&ctx->list_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->list_lock); + qemu_lockcnt_unlock(&ctx->list_lock); return bh; } @@ -93,13 +93,11 @@ int aio_bh_poll(AioContext *ctx) QEMUBH *bh, **bhp, *next; int ret; - ctx->walking_bh++; + qemu_lockcnt_inc(&ctx->list_lock); 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; + for (bh = atomic_rcu_read(&ctx->first_bh); bh; bh = next) { + next = atomic_rcu_read(&bh->next); /* The atomic_xchg is paired with the one in qemu_bh_schedule. The * implicit memory barrier ensures that the callback sees all writes * done by the scheduling thread. It also ensures that the scheduling @@ -116,11 +114,8 @@ int aio_bh_poll(AioContext *ctx) } } - ctx->walking_bh--; - /* remove deleted bhs */ - if (!ctx->walking_bh) { - qemu_mutex_lock(&ctx->list_lock); + if (qemu_lockcnt_dec_and_lock(&ctx->list_lock)) { bhp = &ctx->first_bh; while (*bhp) { bh = *bhp; @@ -131,7 +126,7 @@ int aio_bh_poll(AioContext *ctx) bhp = &bh->next; } } - qemu_mutex_unlock(&ctx->list_lock); + qemu_lockcnt_unlock(&ctx->list_lock); } return ret; @@ -187,7 +182,8 @@ aio_compute_timeout(AioContext *ctx) int timeout = -1; QEMUBH *bh; - for (bh = ctx->first_bh; bh; bh = bh->next) { + for (bh = atomic_rcu_read(&ctx->first_bh); bh; + bh = atomic_rcu_read(&bh->next)) { if (bh->scheduled) { if (bh->idle) { /* idle bottom halves will be polled at least @@ -270,7 +266,8 @@ aio_ctx_finalize(GSource *source) } #endif - qemu_mutex_lock(&ctx->list_lock); + qemu_lockcnt_lock(&ctx->list_lock); + assert(!qemu_lockcnt_count(&ctx->list_lock)); while (ctx->first_bh) { QEMUBH *next = ctx->first_bh->next; @@ -280,12 +277,12 @@ aio_ctx_finalize(GSource *source) g_free(ctx->first_bh); ctx->first_bh = next; } - qemu_mutex_unlock(&ctx->list_lock); + qemu_lockcnt_unlock(&ctx->list_lock); aio_set_event_notifier(ctx, &ctx->notifier, false, NULL, NULL); event_notifier_cleanup(&ctx->notifier); qemu_rec_mutex_destroy(&ctx->lock); - qemu_mutex_destroy(&ctx->list_lock); + qemu_lockcnt_destroy(&ctx->list_lock); timerlistgroup_deinit(&ctx->tlg); } @@ -372,6 +369,7 @@ AioContext *aio_context_new(Error **errp) goto fail; } g_source_set_can_recurse(&ctx->source, true); + qemu_lockcnt_init(&ctx->list_lock); aio_set_event_notifier(ctx, &ctx->notifier, false, (EventNotifierHandler *) @@ -381,7 +379,6 @@ AioContext *aio_context_new(Error **errp) ctx->linux_aio = NULL; #endif ctx->thread_pool = NULL; - qemu_mutex_init(&ctx->list_lock); qemu_rec_mutex_init(&ctx->lock); timerlistgroup_init(&ctx->tlg, aio_timerlist_notify, ctx); |