diff mbox

[09/18] throttle-groups: protect throttled requests with a CoMutex

Message ID 20170525163225.29954-10-pbonzini@redhat.com
State New
Headers show

Commit Message

Paolo Bonzini May 25, 2017, 4:32 p.m. UTC 
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>
---
 block/block-backend.c          |  1 +
 block/throttle-groups.c        | 12 ++++++++++--
 include/sysemu/block-backend.h |  7 ++-----
 3 files changed, 13 insertions(+), 7 deletions(-)

Comments

Alberto Garcia May 29, 2017, 2:24 p.m. UTC | #1 
On Thu 25 May 2017 06:32:16 PM CEST, Paolo Bonzini wrote:
> 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>

Reviewed-by: Alberto Garcia <berto@igalia.com>

Berto
diff mbox

Patch

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