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throttle-groups: protect throttled requests with a CoMutex

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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 <stefanha@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20170605123908.18777-10-pbonzini@redhat.com>
Signed-off-by: Fam Zheng <famz@redhat.com>
This commit is contained in:
Paolo Bonzini 2017-06-05 14:38:58 +02:00 committed by Fam Zheng
parent 3b170dc867
commit 93001e9d87
3 changed files with 13 additions and 7 deletions
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1
block/block-backend.c
View File

@ -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]);

12
block/throttle-groups.c
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@ -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]--;
}

7
include/sysemu/block-backend.h
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@ -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