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block: remove outdated AioContext locking comments

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The AioContext lock no longer exists.

There is one noteworthy change:

  - * More specifically, these functions use BDRV_POLL_WHILE(bs), which
  - * requires the caller to be either in the main thread and hold
  - * the BlockdriverState (bs) AioContext lock, or directly in the
  - * home thread that runs the bs AioContext. Calling them from
  - * another thread in another AioContext would cause deadlocks.
  + * More specifically, these functions use BDRV_POLL_WHILE(bs), which requires
  + * the caller to be either in the main thread or directly in the home thread
  + * that runs the bs AioContext. Calling them from another thread in another
  + * AioContext would cause deadlocks.

I am not sure whether deadlocks are still possible. Maybe they have just
moved to the fine-grained locks that have replaced the AioContext. Since
I am not sure if the deadlocks are gone, I have kept the substance
unchanged and just removed mention of the AioContext.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-ID: <20231205182011.1976568-15-stefanha@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2023-12-05 13:20:11 -05:00 • committed by Kevin Wolf
parent e91083cd3f
commit 23c983c8f6
8 changed files with 22 additions and 82 deletions
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2
tests/qemu-iotests/202
View file

@ -21,7 +21,7 @@
# Check that QMP 'transaction' blockdev-snapshot-sync with multiple drives on a
# single IOThread completes successfully. This particular command triggered a
# hang due to recursive AioContext locking and BDRV_POLL_WHILE(). Protect
# against regressions.
# against regressions even though the AioContext lock no longer exists.
import iotests

3
tests/qemu-iotests/203
View file

@ -21,7 +21,8 @@
# Check that QMP 'migrate' with multiple drives on a single IOThread completes
# successfully. This particular command triggered a hang in the source QEMU
# process due to recursive AioContext locking in bdrv_invalidate_all() and
# BDRV_POLL_WHILE().
# BDRV_POLL_WHILE(). Protect against regressions even though the AioContext
# lock no longer exists.
import iotests