diff mbox series

[v5,5/6] block/blkdebug: remove new_state field and instead use a local variable

Message ID 20210614082931.24925-6-eesposit@redhat.com
State New
Headers show
Series blkdebug: fix racing condition when iterating on | expand

Commit Message

Emanuele Giuseppe Esposito June 14, 2021, 8:29 a.m. UTC 
There seems to be no benefit in using a field. Replace it with a local
variable, and move the state update before the yields.

The state update has do be done before the yields because now using
a local variable does not allow the new updated state to be visible
by the other yields.

Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
---
 block/blkdebug.c | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

Comments

Vladimir Sementsov-Ogievskiy June 19, 2021, 12:38 p.m. UTC | #1 
14.06.2021 11:29, Emanuele Giuseppe Esposito wrote:
> There seems to be no benefit in using a field. Replace it with a local
> variable, and move the state update before the yields.
> 
> The state update has do be done before the yields because now using
> a local variable does not allow the new updated state to be visible
> by the other yields.

Not sure that this sentence helps.. I just can't imagine how state update should work keeping in mind these yields :) And making state update more atomically makes sense to me just because it's simpler to understand.

> 
> Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>

Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
diff mbox series

Patch

diff --git a/block/blkdebug.c b/block/blkdebug.c
index dd82131d1e..b47c3fd97c 100644
--- a/block/blkdebug.c
+++ b/block/blkdebug.c
@@ -40,7 +40,6 @@ 
 
 typedef struct BDRVBlkdebugState {
     int state;
-    int new_state;
     uint64_t align;
     uint64_t max_transfer;
     uint64_t opt_write_zero;
@@ -792,7 +791,7 @@  static void suspend_request(BlockDriverState *bs, BlkdebugRule *rule)
 }
 
 static void process_rule(BlockDriverState *bs, struct BlkdebugRule *rule,
-                         int *action_count)
+                         int *action_count, int *new_state)
 {
     BDRVBlkdebugState *s = bs->opaque;
 
@@ -812,7 +811,7 @@  static void process_rule(BlockDriverState *bs, struct BlkdebugRule *rule,
         break;
 
     case ACTION_SET_STATE:
-        s->new_state = rule->options.set_state.new_state;
+        *new_state = rule->options.set_state.new_state;
         break;
 
     case ACTION_SUSPEND:
@@ -825,21 +824,21 @@  static void blkdebug_debug_event(BlockDriverState *bs, BlkdebugEvent event)
 {
     BDRVBlkdebugState *s = bs->opaque;
     struct BlkdebugRule *rule, *next;
+    int new_state;
     int actions_count[ACTION__MAX] = { 0 };
 
     assert((int)event >= 0 && event < BLKDBG__MAX);
 
-    s->new_state = s->state;
+    new_state = s->state;
     QLIST_FOREACH_SAFE(rule, &s->rules[event], next, next) {
-        process_rule(bs, rule, actions_count);
+        process_rule(bs, rule, actions_count, &new_state);
     }
+    s->state = new_state;
 
     while (actions_count[ACTION_SUSPEND] > 0) {
         qemu_coroutine_yield();
         actions_count[ACTION_SUSPEND]--;
     }
-
-    s->state = s->new_state;
 }
 
 static int blkdebug_debug_breakpoint(BlockDriverState *bs, const char *event,