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author | Stefan Hajnoczi <stefanha@redhat.com> | 2023-04-04 11:33:07 -0400 |
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committer | Kevin Wolf <kwolf@redhat.com> | 2023-05-10 14:15:13 +0200 |
commit | 3edf660a9155848d1d7bc6ad2586ceb0285105e3 (patch) | |
tree | 0c2d12be814859368da9f478aa300b20fb7cae0f | |
parent | 17ac39c3e726173f737bb6cd898c160b406532d4 (diff) | |
download | qemu-3edf660a9155848d1d7bc6ad2586ceb0285105e3.zip qemu-3edf660a9155848d1d7bc6ad2586ceb0285105e3.tar.gz qemu-3edf660a9155848d1d7bc6ad2586ceb0285105e3.tar.bz2 |
aio-wait: avoid AioContext lock in aio_wait_bh_oneshot()
There is no need for the AioContext lock in aio_wait_bh_oneshot().
It's easy to remove the lock from existing callers and then switch from
AIO_WAIT_WHILE() to AIO_WAIT_WHILE_UNLOCKED() in aio_wait_bh_oneshot().
Document that the AioContext lock should not be held across
aio_wait_bh_oneshot(). Holding a lock across aio_poll() can cause
deadlock so we don't want callers to do that.
This is a step towards getting rid of the AioContext lock.
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20230404153307.458883-1-stefanha@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
-rw-r--r-- | hw/block/dataplane/virtio-blk.c | 3 | ||||
-rw-r--r-- | hw/scsi/virtio-scsi-dataplane.c | 2 | ||||
-rw-r--r-- | include/block/aio-wait.h | 2 | ||||
-rw-r--r-- | util/aio-wait.c | 2 |
4 files changed, 4 insertions, 5 deletions
diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c index a620299..af1c24c 100644 --- a/hw/block/dataplane/virtio-blk.c +++ b/hw/block/dataplane/virtio-blk.c @@ -315,9 +315,10 @@ void virtio_blk_data_plane_stop(VirtIODevice *vdev) s->stopping = true; trace_virtio_blk_data_plane_stop(s); - aio_context_acquire(s->ctx); aio_wait_bh_oneshot(s->ctx, virtio_blk_data_plane_stop_bh, s); + aio_context_acquire(s->ctx); + /* Wait for virtio_blk_dma_restart_bh() and in flight I/O to complete */ blk_drain(s->conf->conf.blk); diff --git a/hw/scsi/virtio-scsi-dataplane.c b/hw/scsi/virtio-scsi-dataplane.c index 20bb917..f3214e1 100644 --- a/hw/scsi/virtio-scsi-dataplane.c +++ b/hw/scsi/virtio-scsi-dataplane.c @@ -197,9 +197,7 @@ void virtio_scsi_dataplane_stop(VirtIODevice *vdev) } s->dataplane_stopping = true; - aio_context_acquire(s->ctx); aio_wait_bh_oneshot(s->ctx, virtio_scsi_dataplane_stop_bh, s); - aio_context_release(s->ctx); blk_drain_all(); /* ensure there are no in-flight requests */ diff --git a/include/block/aio-wait.h b/include/block/aio-wait.h index 6e43e3b..5449b6d 100644 --- a/include/block/aio-wait.h +++ b/include/block/aio-wait.h @@ -131,7 +131,7 @@ void aio_wait_kick(void); * * Run a BH in @ctx and wait for it to complete. * - * Must be called from the main loop thread with @ctx acquired exactly once. + * Must be called from the main loop thread without @ctx acquired. * Note that main loop event processing may occur. */ void aio_wait_bh_oneshot(AioContext *ctx, QEMUBHFunc *cb, void *opaque); diff --git a/util/aio-wait.c b/util/aio-wait.c index 98c5acc..b5336cf 100644 --- a/util/aio-wait.c +++ b/util/aio-wait.c @@ -82,5 +82,5 @@ void aio_wait_bh_oneshot(AioContext *ctx, QEMUBHFunc *cb, void *opaque) assert(qemu_get_current_aio_context() == qemu_get_aio_context()); aio_bh_schedule_oneshot(ctx, aio_wait_bh, &data); - AIO_WAIT_WHILE(ctx, !data.done); + AIO_WAIT_WHILE_UNLOCKED(NULL, !data.done); } |