[vlc-devel] [PATCH] video_output: vout_subpictures: prevent deadlock when subpicture heap is full

[Steve Lhomme]

LGTM too but Francois may know better about this code.

On 12/10/2018 08:00, Thomas Guillem wrote:
> Hello,
>
> Thanks for this patch. It is fine for me.
> Waiting reviews from other devs though.
>
> On Fri, Oct 12, 2018, at 03:45, Juan Lledo wrote:
>> In SpuSelectSubpictures(), SpuHeapDeleteAt() only runs when selecting
>> valid subpictures to display. If the subpicture heap is full and all
>> entries are rejected, there will not be any valid subpictures so the
>> for loop is skipped due to "channel_count" being 0.
>>
>> This fix should yield a similar result while avoiding the deadlock due
>> to running in an earlier loop.
>>
>> Fixes #19353. I believe scrolling on a trackpad on Mac could sometimes
>> send events quickly enough that the whole heap would fill up and get
>> invalidated before SpuSelectSubpictures() could run again.
>> ---
>>   src/video_output/vout_subpictures.c | 10 +++++-----
>>   1 file changed, 5 insertions(+), 5 deletions(-)
>>
>> diff --git a/src/video_output/vout_subpictures.c b/src/video_output/
>> vout_subpictures.c
>> index 682461a..04c241f 100644
>> --- a/src/video_output/vout_subpictures.c
>> +++ b/src/video_output/vout_subpictures.c
>> @@ -547,8 +547,11 @@ static void SpuSelectSubpictures(spu_t *spu,
>>   
>>       for (int index = 0; index < VOUT_MAX_SUBPICTURES; index++) {
>>           spu_heap_entry_t *entry = &sys->heap.entry[index];
>> -        if (!entry->subpicture || entry->reject)
>> +        if (!entry->subpicture || entry->reject) {
>> +            if (entry->reject)
>> +                SpuHeapDeleteAt(&sys->heap, index);
>>               continue;
>> +        }
>>           const int i_channel = entry->subpicture->i_channel;
>>           int i;
>>           for (i = 0; i < channel_count; i++) {
>> @@ -578,11 +581,8 @@ static void SpuSelectSubpictures(spu_t *spu,
>>               bool is_stop_valid;
>>               bool is_late;
>>   
>> -            if (!current || entry->reject) {
>> -                if (entry->reject)
>> -                    SpuHeapDeleteAt(&sys->heap, index);
>> +            if (!current || entry->reject)
>>                   continue;
>> -            }
>>   
>>               if (current->i_channel != channel[i] ||
>>                  (ignore_osd && !current->b_subtitle))
>> -- 
>> 2.6.4
>>
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