Re: 回复: [PATCH] drm/amdgpu: fix a bug NULL pointer dereference

[Nirmoy]

Hi Monk,

How  can I reproduce this bug ?

Regards,

Nirmoy

On 2/20/20 4:15 PM, Nirmoy wrote:
>
> On 2/20/20 2:35 PM, Liu, Monk wrote:
>> Sorry, my previous idea still leave RQ null, please check if below 
>> method works:
>>
>> 29 static struct drm_sched_rq *
>> 130 drm_sched_entity_get_free_sched(struct drm_sched_entity *entity)
>> 131 {
>> 132     struct drm_sched_rq *rq = NULL;
>> 133     unsigned int min_jobs = UINT_MAX, num_jobs;
>> 134     int i;
>>
>> 135
>>         While (!mutex_trylock(....))
>>             Sleep()
> We can't do that drm_sched_entity_get_free_sched is in another 
> module(drm scheduler) independent of amdgpu
>> 136     for (i = 0; i < entity->num_rq_list; ++i) {
>> 137         struct drm_gpu_scheduler *sched = entity->rq_list[i]->sched;
>> 138
>> 139         if (!entity->rq_list[i]->sched->ready) { //we take the 
>> gpu reset mutex lock, so now sched->ready won't be set to "not ready"
>> 140             DRM_WARN("sched%s is not ready, skipping", sched->name);
>> 141             continue;
>> 142         }
>> 143
>> 144         num_jobs = atomic_read(&sched->num_jobs);
>> 145         if (num_jobs < min_jobs) {
>> 146             min_jobs = num_jobs;
>> 147             rq = entity->rq_list[i];
>> 148         }
>> 149     }
>>
>>         Mutex_unlock(...)
>>
>> 150
>> 151     return rq;
>> 152 }
>>
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