[Qemu-devel] [PATCH 08/17] throttle-groups: protect throttled requests with a CoMutex

[Paolo Bonzini]

Signed-off-by: Paolo Bonzini <address@hidden>
---
 block/block-backend.c          |  1 +
 block/throttle-groups.c        | 11 +++++++++--
 include/sysemu/block-backend.h |  7 ++-----
 3 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/block/block-backend.c b/block/block-backend.c
index 915ccc5..a37d74d 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -163,6 +163,7 @@ 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.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 d66bf62..695d28d 100644
--- a/block/throttle-groups.c
+++ b/block/throttle-groups.c
@@ -268,8 +268,13 @@ static bool throttle_group_schedule_timer(BlockBackend 
*blk, bool is_write)
 static bool 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->reqs_lock);
+    ret = qemu_co_queue_next(&blkp->throttled_reqs[is_write]);
+    qemu_co_mutex_unlock(&blkp->reqs_lock);
+
+    return ret;
 }
 
 /* Look for the next pending I/O request and schedule it.
@@ -338,7 +343,9 @@ 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->reqs_lock);
+        qemu_co_queue_wait(&blkp->throttled_reqs[is_write], &blkp->reqs_lock);
+        qemu_co_mutex_unlock(&blkp->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 87a43b0..e9529fb 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.  */
+    /* reqs_lock protects the CoQueues for throttled requests.  */
+    CoMutex      reqs_lock;
     CoQueue      throttled_reqs[2];
 
     /* Nonzero if the I/O limits are currently being ignored; generally
-- 
2.9.3