From 3edf660a9155848d1d7bc6ad2586ceb0285105e3 Mon Sep 17 00:00:00 2001 From: Stefan Hajnoczi Date: Tue, 4 Apr 2023 11:33:07 -0400 Subject: 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 Signed-off-by: Stefan Hajnoczi Message-Id: <20230404153307.458883-1-stefanha@redhat.com> Reviewed-by: Paolo Bonzini Reviewed-by: Emanuele Giuseppe Esposito Reviewed-by: Kevin Wolf Signed-off-by: Kevin Wolf --- hw/block/dataplane/virtio-blk.c | 3 ++- hw/scsi/virtio-scsi-dataplane.c | 2 -- include/block/aio-wait.h | 2 +- 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); } -- cgit v1.1