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e92f0e1910
BDRV_POLL_WHILE waits for the started I/O by releasing bs's ctx then polling
the main context, which relies on the yielded coroutine continuing on bs->ctx
before notifying qemu_aio_context with bdrv_wakeup().
Thus, using qemu_coroutine_enter to start I/O is wrong because if the coroutine
is entered from main loop, co->ctx will be qemu_aio_context, as a result of the
"release, poll, acquire" loop of BDRV_POLL_WHILE, race conditions happen when
both main thread and the iothread access the same BDS:
main loop iothread
-----------------------------------------------------------------------
blockdev_snapshot
aio_context_acquire(bs->ctx)
virtio_scsi_data_plane_handle_cmd
bdrv_drained_begin(bs->ctx)
bdrv_flush(bs)
bdrv_co_flush(bs) aio_context_acquire(bs->ctx).enter
...
qemu_coroutine_yield(co)
BDRV_POLL_WHILE()
aio_context_release(bs->ctx)
aio_context_acquire(bs->ctx).return
...
aio_co_wake(co)
aio_poll(qemu_aio_context) ...
co_schedule_bh_cb() ...
qemu_coroutine_enter(co) ...
/* (A) bdrv_co_flush(bs) /* (B) I/O on bs */
continues... */
aio_context_release(bs->ctx)
aio_context_acquire(bs->ctx)
Note that in above case, bdrv_drained_begin() doesn't do the "release,
poll, acquire" in BDRV_POLL_WHILE, because bs->in_flight == 0.
Fix this by using bdrv_coroutine_enter and enter coroutine in the right
context.
iotests 109 output is updated because the coroutine reenter flow during
mirror job complete is different (now through co_queue_wakeup, instead
of the unconditional qemu_coroutine_switch before), making the end job
len different.
Signed-off-by: Fam Zheng <famz@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
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| .. | ||
| accounting.c | ||
| backup.c | ||
| blkdebug.c | ||
| blkreplay.c | ||
| blkverify.c | ||
| block-backend.c | ||
| bochs.c | ||
| cloop.c | ||
| commit.c | ||
| crypto.c | ||
| curl.c | ||
| dirty-bitmap.c | ||
| dmg-bz2.c | ||
| dmg.c | ||
| dmg.h | ||
| file-posix.c | ||
| file-win32.c | ||
| gluster.c | ||
| io.c | ||
| iscsi-opts.c | ||
| iscsi.c | ||
| linux-aio.c | ||
| Makefile.objs | ||
| mirror.c | ||
| nbd-client.c | ||
| nbd-client.h | ||
| nbd.c | ||
| nfs.c | ||
| null.c | ||
| parallels.c | ||
| qapi.c | ||
| qcow2-cache.c | ||
| qcow2-cluster.c | ||
| qcow2-refcount.c | ||
| qcow2-snapshot.c | ||
| qcow2.c | ||
| qcow2.h | ||
| qcow.c | ||
| qed-check.c | ||
| qed-cluster.c | ||
| qed-gencb.c | ||
| qed-l2-cache.c | ||
| qed-table.c | ||
| qed.c | ||
| qed.h | ||
| quorum.c | ||
| raw-format.c | ||
| rbd.c | ||
| replication.c | ||
| sheepdog.c | ||
| snapshot.c | ||
| ssh.c | ||
| stream.c | ||
| throttle-groups.c | ||
| trace-events | ||
| vdi.c | ||
| vhdx-endian.c | ||
| vhdx-log.c | ||
| vhdx.c | ||
| vhdx.h | ||
| vmdk.c | ||
| vpc.c | ||
| vvfat.c | ||
| win32-aio.c | ||
| write-threshold.c | ||