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From: "Christian König" <christian.koenig@amd.com>
To: "Thomas Hellström" <thomas.hellstrom@linux.intel.com>,
	"Maarten Lankhorst" <maarten.lankhorst@linux.intel.com>,
	intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org
Cc: linaro-mm-sig@lists.linaro.org, matthew.auld@intel.com
Subject: Re: [RFC PATCH 1/2] dma-fence: Avoid establishing a locking order between fence classes
Date: Tue, 30 Nov 2021 13:42:04 +0100	[thread overview]
Message-ID: <52a7cf8c-59c7-fec0-2274-d19bdc505314@amd.com> (raw)
In-Reply-To: <b440cfbc-2b9a-1aa2-76d6-17337f835777@linux.intel.com>

Am 30.11.21 um 13:31 schrieb Thomas Hellström:
> [SNIP]
>> Other than that, I didn't investigate the nesting fails enough to say 
>> I can accurately review this. :)
>
> Basically the problem is that within enable_signaling() which is 
> called with the dma_fence lock held, we take the dma_fence lock of 
> another fence. If that other fence is a dma_fence_array, or a 
> dma_fence_chain which in turn tries to lock a dma_fence_array we hit a 
> splat.

Yeah, I already thought that you constructed something like that.

You get the splat because what you do here is illegal, you can't mix 
dma_fence_array and dma_fence_chain like this or you can end up in a 
stack corruption.

Regards,
Christian.

>
> But I'll update the commit message with a typical splat.
>
> /Thomas


  reply	other threads:[~2021-11-30 12:42 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-30 12:19 [RFC PATCH 0/2] Attempt to avoid dma-fence-[chain|array] lockdep splats Thomas Hellström
2021-11-30 12:19 ` [RFC PATCH 1/2] dma-fence: Avoid establishing a locking order between fence classes Thomas Hellström
2021-11-30 12:25   ` Maarten Lankhorst
2021-11-30 12:31     ` Thomas Hellström
2021-11-30 12:42       ` Christian König [this message]
2021-11-30 12:56         ` Thomas Hellström
2021-11-30 13:26           ` Christian König
2021-11-30 14:35             ` Thomas Hellström
2021-11-30 15:02               ` Christian König
2021-11-30 18:12                 ` Thomas Hellström
2021-11-30 19:27                   ` Thomas Hellström
2021-12-01  7:05                     ` Christian König
2021-12-01  8:23                       ` [Linaro-mm-sig] " Thomas Hellström (Intel)
2021-12-01  8:36                         ` Christian König
2021-12-01 10:15                           ` Thomas Hellström (Intel)
2021-12-01 10:32                             ` Christian König
2021-12-01 11:04                               ` Thomas Hellström (Intel)
2021-12-01 11:25                                 ` Christian König
2021-12-01 12:16                                   ` Thomas Hellström (Intel)
2021-12-03 13:08                                     ` Christian König
2021-12-03 14:18                                       ` Thomas Hellström
2021-12-03 14:26                                         ` Christian König
2021-12-03 14:50                                           ` Thomas Hellström
2021-12-03 15:00                                             ` Christian König
2021-12-03 15:13                                               ` Thomas Hellström (Intel)
2021-12-07 18:08                                         ` [Intel-gfx] " Daniel Vetter
2021-12-07 20:46                                           ` Thomas Hellström
2021-12-20  9:37                                             ` Daniel Vetter
2021-11-30 12:32   ` Thomas Hellström
2021-11-30 12:19 ` [RFC PATCH 2/2] dma-fence: Avoid excessive recursive fence locking from enable_signaling() callbacks Thomas Hellström
2021-11-30 12:36 ` [RFC PATCH 0/2] Attempt to avoid dma-fence-[chain|array] lockdep splats Christian König

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