[PULL 4/6] blkdebug: do not suspend in the middle of QLIST_FOREACH_SAFE

From: Max Reitz <mreitz@redhat.com>
To: qemu-block@nongnu.org
Cc: Kevin Wolf <kwolf@redhat.com>,
	Peter Maydell <peter.maydell@linaro.org>,
	qemu-devel@nongnu.org, Max Reitz <mreitz@redhat.com>
Subject: [PULL 4/6] blkdebug: do not suspend in the middle of QLIST_FOREACH_SAFE
Date: Mon, 19 Jul 2021 19:26:56 +0200	[thread overview]
Message-ID: <20210719172658.715442-5-mreitz@redhat.com> (raw)
In-Reply-To: <20210719172658.715442-1-mreitz@redhat.com>

From: Emanuele Giuseppe Esposito <eesposit@redhat.com>

That would be unsafe in case a rule other than the current one
is removed while the coroutine has yielded.
Keep FOREACH_SAFE because suspend_request deletes the current rule.

After this patch, *all* matching rules are deleted before suspending
the coroutine, rather than just one.
This doesn't affect the existing testcases.

Use actions_count to see how many yield to issue.

Co-developed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20210614082931.24925-5-eesposit@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
---
 block/blkdebug.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/block/blkdebug.c b/block/blkdebug.c
index 6bdeb2c7b3..dd82131d1e 100644
--- a/block/blkdebug.c
+++ b/block/blkdebug.c
@@ -789,7 +789,6 @@ static void suspend_request(BlockDriverState *bs, BlkdebugRule *rule)
     if (!qtest_enabled()) {
         printf("blkdebug: Suspended request '%s'\n", r->tag);
     }
-    qemu_coroutine_yield();
 }
 
 static void process_rule(BlockDriverState *bs, struct BlkdebugRule *rule,
@@ -834,6 +833,12 @@ static void blkdebug_debug_event(BlockDriverState *bs, BlkdebugEvent event)
     QLIST_FOREACH_SAFE(rule, &s->rules[event], next, next) {
         process_rule(bs, rule, actions_count);
     }
+
+    while (actions_count[ACTION_SUSPEND] > 0) {
+        qemu_coroutine_yield();
+        actions_count[ACTION_SUSPEND]--;
+    }
+
     s->state = s->new_state;
 }
 
-- 
2.31.1


