Another possibility is to use tg->lock, which we're holding anyway in
both schedule_next_request and throttle_group_co_io_limits_intercept.
This would require open-coding the CoQueue however, so I've chosen this
alternative.
Reviewed-by: Stefan Hajnoczi <stefa...@redhat.com>
Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
---
block/block-backend.c | 1 +
block/throttle-groups.c | 12 ++++++++++--
include/sysemu/block-backend.h | 7 ++-----
3 files changed, 13 insertions(+), 7 deletions(-)
diff --git a/block/block-backend.c b/block/block-backend.c
index e50ec03..be2ddf1 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -216,6 +216,7 @@ BlockBackend *blk_new(uint64_t perm, uint64_t shared_perm)
blk->shared_perm = shared_perm;
blk_set_enable_write_cache(blk, true);
+ qemu_co_mutex_init(&blk->public.throttled_reqs_lock);
qemu_co_queue_init(&blk->public.throttled_reqs[0]);
qemu_co_queue_init(&blk->public.throttled_reqs[1]);
diff --git a/block/throttle-groups.c b/block/throttle-groups.c
index 8bf1031..a181cb1 100644
--- a/block/throttle-groups.c
+++ b/block/throttle-groups.c
@@ -270,8 +270,13 @@ static bool coroutine_fn
throttle_group_co_restart_queue(BlockBackend *blk,
bool is_write)
{
BlockBackendPublic *blkp = blk_get_public(blk);
+ bool ret;
- return qemu_co_queue_next(&blkp->throttled_reqs[is_write]);
+ qemu_co_mutex_lock(&blkp->throttled_reqs_lock);
+ ret = qemu_co_queue_next(&blkp->throttled_reqs[is_write]);
+ qemu_co_mutex_unlock(&blkp->throttled_reqs_lock);
+
+ return ret;
}
/* Look for the next pending I/O request and schedule it.
@@ -340,7 +345,10 @@ void coroutine_fn
throttle_group_co_io_limits_intercept(BlockBackend *blk,
if (must_wait || blkp->pending_reqs[is_write]) {
blkp->pending_reqs[is_write]++;
qemu_mutex_unlock(&tg->lock);
- qemu_co_queue_wait(&blkp->throttled_reqs[is_write], NULL);
+ qemu_co_mutex_lock(&blkp->throttled_reqs_lock);
+ qemu_co_queue_wait(&blkp->throttled_reqs[is_write],
+ &blkp->throttled_reqs_lock);
+ qemu_co_mutex_unlock(&blkp->throttled_reqs_lock);
qemu_mutex_lock(&tg->lock);
blkp->pending_reqs[is_write]--;
}
diff --git a/include/sysemu/block-backend.h b/include/sysemu/block-backend.h
index 24b63d6..999eb23 100644
--- a/include/sysemu/block-backend.h
+++ b/include/sysemu/block-backend.h
@@ -72,11 +72,8 @@ typedef struct BlockDevOps {
* fields that must be public. This is in particular for QLIST_ENTRY() and
* friends so that BlockBackends can be kept in lists outside block-backend.c
*/
typedef struct BlockBackendPublic {
- /* I/O throttling has its own locking, but also some fields are
- * protected by the AioContext lock.
- */
-
- /* Protected by AioContext lock. */
+ /* throttled_reqs_lock protects the CoQueues for throttled requests. */
+ CoMutex throttled_reqs_lock;
CoQueue throttled_reqs[2];
/* Nonzero if the I/O limits are currently being ignored; generally
--
1.8.3.1
