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[Qemu-devel] [PATCH v3 08/19] block: Add missing locking in bdrv_co_drai
From: |
Kevin Wolf |
Subject: |
[Qemu-devel] [PATCH v3 08/19] block: Add missing locking in bdrv_co_drain_bh_cb() |
Date: |
Thu, 20 Sep 2018 18:19:47 +0200 |
bdrv_do_drained_begin/end() assume that they are called with the
AioContext lock of bs held. If we call drain functions from a coroutine
with the AioContext lock held, we yield and schedule a BH to move out of
coroutine context. This means that the lock for the home context of the
coroutine is released and must be re-acquired in the bottom half.
Signed-off-by: Kevin Wolf <address@hidden>
Reviewed-by: Max Reitz <address@hidden>
---
include/qemu/coroutine.h | 5 +++++
block/io.c | 15 +++++++++++++++
util/qemu-coroutine.c | 5 +++++
3 files changed, 25 insertions(+)
diff --git a/include/qemu/coroutine.h b/include/qemu/coroutine.h
index 6f8a487041..9801e7f5a4 100644
--- a/include/qemu/coroutine.h
+++ b/include/qemu/coroutine.h
@@ -90,6 +90,11 @@ void qemu_aio_coroutine_enter(AioContext *ctx, Coroutine
*co);
void coroutine_fn qemu_coroutine_yield(void);
/**
+ * Get the AioContext of the given coroutine
+ */
+AioContext *coroutine_fn qemu_coroutine_get_aio_context(Coroutine *co);
+
+/**
* Get the currently executing coroutine
*/
Coroutine *coroutine_fn qemu_coroutine_self(void);
diff --git a/block/io.c b/block/io.c
index 7100344c7b..914ba78f1a 100644
--- a/block/io.c
+++ b/block/io.c
@@ -288,6 +288,18 @@ static void bdrv_co_drain_bh_cb(void *opaque)
BlockDriverState *bs = data->bs;
if (bs) {
+ AioContext *ctx = bdrv_get_aio_context(bs);
+ AioContext *co_ctx = qemu_coroutine_get_aio_context(co);
+
+ /*
+ * When the coroutine yielded, the lock for its home context was
+ * released, so we need to re-acquire it here. If it explicitly
+ * acquired a different context, the lock is still held and we don't
+ * want to lock it a second time (or AIO_WAIT_WHILE() would hang).
+ */
+ if (ctx == co_ctx) {
+ aio_context_acquire(ctx);
+ }
bdrv_dec_in_flight(bs);
if (data->begin) {
bdrv_do_drained_begin(bs, data->recursive, data->parent,
@@ -296,6 +308,9 @@ static void bdrv_co_drain_bh_cb(void *opaque)
bdrv_do_drained_end(bs, data->recursive, data->parent,
data->ignore_bds_parents);
}
+ if (ctx == co_ctx) {
+ aio_context_release(ctx);
+ }
} else {
assert(data->begin);
bdrv_drain_all_begin();
diff --git a/util/qemu-coroutine.c b/util/qemu-coroutine.c
index 1ba4191b84..2295928d33 100644
--- a/util/qemu-coroutine.c
+++ b/util/qemu-coroutine.c
@@ -198,3 +198,8 @@ bool qemu_coroutine_entered(Coroutine *co)
{
return co->caller;
}
+
+AioContext *coroutine_fn qemu_coroutine_get_aio_context(Coroutine *co)
+{
+ return co->ctx;
+}
--
2.13.6
- [Qemu-devel] [PATCH v3 00/19] Fix some jobs/drain/aio_poll related hangs, Kevin Wolf, 2018/09/20
- [Qemu-devel] [PATCH v3 02/19] blockjob: Wake up BDS when job becomes idle, Kevin Wolf, 2018/09/20
- [Qemu-devel] [PATCH v3 01/19] job: Fix missing locking due to mismerge, Kevin Wolf, 2018/09/20
- [Qemu-devel] [PATCH v3 03/19] aio-wait: Increase num_waiters even in home thread, Kevin Wolf, 2018/09/20
- [Qemu-devel] [PATCH v3 05/19] test-blockjob: Acquire AioContext around job_cancel_sync(), Kevin Wolf, 2018/09/20
- [Qemu-devel] [PATCH v3 04/19] test-bdrv-drain: Drain with block jobs in an I/O thread, Kevin Wolf, 2018/09/20
- [Qemu-devel] [PATCH v3 06/19] job: Use AIO_WAIT_WHILE() in job_finish_sync(), Kevin Wolf, 2018/09/20
- [Qemu-devel] [PATCH v3 09/19] block-backend: Add .drained_poll callback, Kevin Wolf, 2018/09/20
- [Qemu-devel] [PATCH v3 11/19] block-backend: Decrease in_flight only after callback, Kevin Wolf, 2018/09/20
- [Qemu-devel] [PATCH v3 08/19] block: Add missing locking in bdrv_co_drain_bh_cb(),
Kevin Wolf <=
- [Qemu-devel] [PATCH v3 12/19] blockjob: Lie better in child_job_drained_poll(), Kevin Wolf, 2018/09/20
- [Qemu-devel] [PATCH v3 13/19] block: Remove aio_poll() in bdrv_drain_poll variants, Kevin Wolf, 2018/09/20
- [Qemu-devel] [PATCH v3 10/19] block-backend: Fix potential double blk_delete(), Kevin Wolf, 2018/09/20
- [Qemu-devel] [PATCH v3 14/19] test-bdrv-drain: Test nested poll in bdrv_drain_poll_top_level(), Kevin Wolf, 2018/09/20
- [Qemu-devel] [PATCH v3 07/19] test-bdrv-drain: Test AIO_WAIT_WHILE() in completion callback, Kevin Wolf, 2018/09/20
- [Qemu-devel] [PATCH v3 15/19] job: Avoid deadlocks in job_completed_txn_abort(), Kevin Wolf, 2018/09/20
- [Qemu-devel] [PATCH v3 16/19] test-bdrv-drain: AIO_WAIT_WHILE() in job .commit/.abort, Kevin Wolf, 2018/09/20
- [Qemu-devel] [PATCH v3 17/19] test-bdrv-drain: Fix outdated comments, Kevin Wolf, 2018/09/20
- [Qemu-devel] [PATCH v3 19/19] test-bdrv-drain: Test draining job source child and parent, Kevin Wolf, 2018/09/20