linux-kernel - Re: [PATCH 09/19] drm/radeon: handle lockup in delayed work, v2

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Message-ID: <53DFBD2E.5070001@amd.com>
Date:	Mon, 4 Aug 2014 19:04:46 +0200
From:	Christian König <christian.koenig@....com>
To:	Maarten Lankhorst <maarten.lankhorst@...onical.com>,
	<airlied@...ux.ie>
CC:	<thellstrom@...are.com>, <nouveau@...ts.freedesktop.org>,
	<linux-kernel@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>,
	<bskeggs@...hat.com>, <alexander.deucher@....com>
Subject: Re: [PATCH 09/19] drm/radeon: handle lockup in delayed work, v2

Am 04.08.2014 um 17:09 schrieb Maarten Lankhorst:
> op 04-08-14 17:04, Christian König schreef:
>> Am 04.08.2014 um 16:58 schrieb Maarten Lankhorst:
>>> op 04-08-14 16:45, Christian König schreef:
>>>> Am 04.08.2014 um 16:40 schrieb Maarten Lankhorst:
>>>>> op 04-08-14 16:37, Christian König schreef:
>>>>>>> It'a pain to deal with gpu reset.
>>>>>> Yeah, well that's nothing new.
>>>>>>
>>>>>>> I've now tried other solutions but that would mean reverting to the old style during gpu lockup recovery, and only running the delayed work when !lockup.
>>>>>>> But this meant that the timeout was useless to add. I think the cleanest is keeping the v2 patch, because potentially any waiting code can be called during lockup recovery.
>>>>>> The lockup code itself should never call any waiting code and V2 doesn't seem to handle a couple of cases correctly either.
>>>>>>
>>>>>> How about moving the fence waiting out of the reset code?
>>>>> What cases did I miss then?
>>>>>
>>>>> I'm curious how you want to move the fence waiting out of reset, when there are so many places that could potentially wait, like radeon_ib_get can call radeon_sa_bo_new which can do a wait, or radeon_ring_alloc that can wait on radeon_fence_wait_next, etc.
>>>> The IB test itself doesn't needs to be protected by the exclusive lock. Only everything between radeon_save_bios_scratch_regs and radeon_ring_restore.
>>> I'm not sure about that, what do you want to do if the ring tests fail? Do you have to retake the exclusive lock?
>> Just set need_reset again and return -EAGAIN, that should have mostly the same effect as what we are doing right now.
> Yeah, except for the locking the ttm delayed workqueue, but that bool should be easy to save/restore.
> I think this could work.

Actually you could activate the delayed workqueue much earlier as well.

Thinking more about it that sounds like a bug in the current code, 
because we probably want the workqueue activated before waiting for the 
fence.

Christian.

>
> ~Maarten
>

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