Re: [PATCH] drm/syncobj: Avoid kmalloc(GFP_KERNEL) under spinlock

[zhoucm1 <zhoucm1@amd.com>]

Thanks, Could you help to submit to drm-misc again?

-David


On 2018年10月26日 15:43, Christian König wrote:
> Am 26.10.18 um 08:20 schrieb Chunming Zhou:
>> drivers/gpu/drm/drm_syncobj.c:202:4-14: ERROR: function 
>> drm_syncobj_find_signal_pt_for_point called on line 390 inside lock 
>> on line 389 but uses GFP_KERNEL
>>
>>    Find functions that refer to GFP_KERNEL but are called with locks 
>> held.
>>
>> Generated by: scripts/coccinelle/locks/call_kern.cocci
>>
>> v2:
>> syncobj->timeline still needs protect.
>>
>> v3:
>> use a global signaled fence instead of re-allocation.
>>
>> v4:
>> Don't need moving lock.
>> Don't expose func.
>>
>> v5:
>> rename func and directly return.
>>
>> Tested by: syncobj_wait and ./deqp-vk -n dEQP-VK.*semaphore* with
>> lock debug kernel options enabled.
>>
>> Signed-off-by: Chunming Zhou <david1.zhou@amd.com>
>> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
>> Cc: intel-gfx@lists.freedesktop.org
>> Cc: Christian König <easy2remember.chk@googlemail.com>
>> Cc: Chris Wilson <chris@chris-wilson.co.uk>
>> CC: Julia Lawall <julia.lawall@lip6.fr>
>> Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
>
> Reviewed-by: Christian König <christian.koenig@amd.com>
>
>> ---
>>   drivers/gpu/drm/drm_syncobj.c | 36 ++++++++++++++++++-----------------
>>   1 file changed, 19 insertions(+), 17 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_syncobj.c 
>> b/drivers/gpu/drm/drm_syncobj.c
>> index b7eaa603f368..d1c6f21c72b5 100644
>> --- a/drivers/gpu/drm/drm_syncobj.c
>> +++ b/drivers/gpu/drm/drm_syncobj.c
>> @@ -80,6 +80,23 @@ struct drm_syncobj_signal_pt {
>>       struct list_head list;
>>   };
>>   +static DEFINE_SPINLOCK(signaled_fence_lock);
>> +static struct dma_fence signaled_fence;
>> +
>> +static struct dma_fence *drm_syncobj_get_stub_fence(void)
>> +{
>> +    spin_lock(&signaled_fence_lock);
>> +    if (!signaled_fence.ops) {
>> +        dma_fence_init(&signaled_fence,
>> +                   &drm_syncobj_stub_fence_ops,
>> +                   &signaled_fence_lock,
>> +                   0, 0);
>> +        dma_fence_signal_locked(&signaled_fence);
>> +    }
>> +    spin_unlock(&signaled_fence_lock);
>> +
>> +    return dma_fence_get(&signaled_fence);
>> +}
>>   /**
>>    * drm_syncobj_find - lookup and reference a sync object.
>>    * @file_private: drm file private pointer
>> @@ -113,23 +130,8 @@ static struct dma_fence
>>       struct drm_syncobj_signal_pt *signal_pt;
>>         if ((syncobj->type == DRM_SYNCOBJ_TYPE_TIMELINE) &&
>> -        (point <= syncobj->timeline)) {
>> -        struct drm_syncobj_stub_fence *fence =
>> -            kzalloc(sizeof(struct drm_syncobj_stub_fence),
>> -                GFP_KERNEL);
>> -
>> -        if (!fence)
>> -            return NULL;
>> -        spin_lock_init(&fence->lock);
>> -        dma_fence_init(&fence->base,
>> -                   &drm_syncobj_stub_fence_ops,
>> -                   &fence->lock,
>> -                   syncobj->timeline_context,
>> -                   point);
>> -
>> -        dma_fence_signal(&fence->base);
>> -        return &fence->base;
>> -    }
>> +        (point <= syncobj->timeline))
>> +        return drm_syncobj_get_stub_fence();
>>         list_for_each_entry(signal_pt, &syncobj->signal_pt_list, list) {
>>           if (point > signal_pt->value)
>

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