Re: [FFmpeg-devel] [PATCH v2] hwcontext_vulkan: workaround MoltenVK's bug which leads to segmentation fault

["\"zhilizhao(赵志立)\"" <quinkblack@foxmail.com>]

> On Jan 27, 2022, at 5:07 PM, Lynne <dev@lynne.ee> wrote:
> 
> 27 Jan 2022, 09:38 by quinkblack@foxmail.com:
> 
>> MoltenVK doesn't reset instance when CreateInstance() failed,
>> then DestroyInstance() leads to segmentation fault. MoltenVK's bug
>> has been fixed by [1], which doesn't available on homebrew yet.
>> Regardless MoltenVK's bug, we shouldn't call DestroyInstance()
>> in the case of CreateInstance() failed, so reset instance making
>> sense.
>> 
>> [1] https://github.com/KhronosGroup/MoltenVK/commit/86a1fbdb8
>> ---
>> libavutil/hwcontext_vulkan.c | 2 ++
>> 1 file changed, 2 insertions(+)
>> 
>> diff --git a/libavutil/hwcontext_vulkan.c b/libavutil/hwcontext_vulkan.c
>> index 2e219511c9..d3bd37a6a7 100644
>> --- a/libavutil/hwcontext_vulkan.c
>> +++ b/libavutil/hwcontext_vulkan.c
>> @@ -719,6 +719,8 @@ static int create_instance(AVHWDeviceContext *ctx, AVDictionary *opts)
>> if (ret != VK_SUCCESS) {
>> av_log(ctx, AV_LOG_ERROR, "Instance creation failure: %s\n",
>> vk_ret2str(ret));
>> +        /* Workaround MoltenVK's bug which doesn't reset instance. */
>> +        hwctx->inst = VK_NULL_HANDLE;
>> err = AVERROR_EXTERNAL;
>> goto fail;
>> }
>> 
> 
> Not a fan of working around this implementation bug.
> Couldn't homebrew just update?

I don’t have strong opinion on the patch, feel free to drop it.

It’s a cheap workaround and it takes a lot of time for me to figure
out the crash. Other people may confront the same issue, then the
patch can be seen as a reference.

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