Re: [PATCH 4/5] blkdebug: do not suspend in the middle of QLIST_FOREACH_SAFE

[Paolo Bonzini <pbonzini@redhat.com>]

On 08/04/21 17:59, Emanuele Giuseppe Esposito wrote:

Perhaps insert here:

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 yeld to issue.
> 
> Co-developed-by: Paolo Bonzini <pbonzini@redhat.com>
> Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
> ---
>   block/blkdebug.c | 7 ++++++-
>   1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/block/blkdebug.c b/block/blkdebug.c
> index 388b5ed615..dffd869b32 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;
>   }
>   
>