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[PULL 10/11] block: Start/end drain on correct AioContext
From: |
Kevin Wolf |
Subject: |
[PULL 10/11] block: Start/end drain on correct AioContext |
Date: |
Fri, 11 Nov 2022 16:27:43 +0100 |
From: Hanna Reitz <hreitz@redhat.com>
bdrv_parent_drained_{begin,end}_single() are supposed to operate on the
parent, not on the child, so they should not attempt to get the context
to poll from the child but the parent instead. BDRV_POLL_WHILE(c->bs)
does get the context from the child, so we should replace it with
AIO_WAIT_WHILE() on the parent's context instead.
This problem becomes apparent when bdrv_replace_child_noperm() invokes
bdrv_parent_drained_end_single() after removing a child from a subgraph
that is in an I/O thread. By the time bdrv_parent_drained_end_single()
is called, child->bs is NULL, and so BDRV_POLL_WHILE(c->bs, ...) will
poll the main loop instead of the I/O thread; but anything that
bdrv_parent_drained_end_single_no_poll() may have scheduled is going to
want to run in the I/O thread, but because we poll the main loop, the
I/O thread is never unpaused, and nothing is run, resulting in a
deadlock.
Closes: https://gitlab.com/qemu-project/qemu/-/issues/1215
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Hanna Reitz <hreitz@redhat.com>
Message-Id: <20221107151321.211175-4-hreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
block/io.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/block/io.c b/block/io.c
index 34b30e304e..b9424024f9 100644
--- a/block/io.c
+++ b/block/io.c
@@ -71,9 +71,10 @@ static void bdrv_parent_drained_end_single_no_poll(BdrvChild
*c,
void bdrv_parent_drained_end_single(BdrvChild *c)
{
int drained_end_counter = 0;
+ AioContext *ctx = bdrv_child_get_parent_aio_context(c);
IO_OR_GS_CODE();
bdrv_parent_drained_end_single_no_poll(c, &drained_end_counter);
- BDRV_POLL_WHILE(c->bs, qatomic_read(&drained_end_counter) > 0);
+ AIO_WAIT_WHILE(ctx, qatomic_read(&drained_end_counter) > 0);
}
static void bdrv_parent_drained_end(BlockDriverState *bs, BdrvChild *ignore,
@@ -116,13 +117,14 @@ static bool bdrv_parent_drained_poll(BlockDriverState
*bs, BdrvChild *ignore,
void bdrv_parent_drained_begin_single(BdrvChild *c, bool poll)
{
+ AioContext *ctx = bdrv_child_get_parent_aio_context(c);
IO_OR_GS_CODE();
c->parent_quiesce_counter++;
if (c->klass->drained_begin) {
c->klass->drained_begin(c);
}
if (poll) {
- BDRV_POLL_WHILE(c->bs, bdrv_parent_drained_poll_single(c));
+ AIO_WAIT_WHILE(ctx, bdrv_parent_drained_poll_single(c));
}
}
--
2.38.1
- [PULL 03/11] block/mirror: Fix NULL s->job in active writes, (continued)
- [PULL 03/11] block/mirror: Fix NULL s->job in active writes, Kevin Wolf, 2022/11/11
- [PULL 04/11] iotests/151: Test that active mirror progresses, Kevin Wolf, 2022/11/11
- [PULL 02/11] block/mirror: Drop mirror_wait_for_any_operation(), Kevin Wolf, 2022/11/11
- [PULL 01/11] block/mirror: Do not wait for active writes, Kevin Wolf, 2022/11/11
- [PULL 06/11] qapi/block-core: Fix BlockdevOptionsNvmeIoUring @path description, Kevin Wolf, 2022/11/11
- [PULL 05/11] iotests/151: Test active requests on mirror start, Kevin Wolf, 2022/11/11
- [PULL 07/11] block/blkio: Set BlockDriver::has_variable_length to false, Kevin Wolf, 2022/11/11
- [PULL 08/11] block: Make bdrv_child_get_parent_aio_context I/O, Kevin Wolf, 2022/11/11
- [PULL 09/11] block-backend: Update ctx immediately after root, Kevin Wolf, 2022/11/11
- [PULL 11/11] tests/stream-under-throttle: New test, Kevin Wolf, 2022/11/11
- [PULL 10/11] block: Start/end drain on correct AioContext,
Kevin Wolf <=
- Re: [PULL 00/11] Block layer patches, Stefan Hajnoczi, 2022/11/11