op 07-03-14 12:18, Sebastian Andrzej Siewior schreef:
* Fernando Lopez-Lezcano | 2014-03-01 17:48:29 [-0800]:
On 02/23/2014 10:47 AM, Sebastian Andrzej Siewior wrote:
Dear RT folks!
I'm pleased to announce the v3.12.12-rt19 patch set.
Just hit this Oops in my desktop at home:
[22328.388996] BUG: unable to handle kernel NULL pointer dereference
at 0000000000000008
[22328.389013] IP: [<ffffffffa011a912>]
nouveau_fence_wait_uevent.isra.2+0x22/0x440 [nouveau]
This is
| static int
| nouveau_fence_wait_uevent(struct nouveau_fence *fence, bool intr)
|
| {
| struct nouveau_channel *chan = fence->channel;
| struct nouveau_fifo *pfifo = nouveau_fifo(chan->drm->device);
and chan is NULL.
[22328.389046] RAX: 0000000000000000 RBX: ffff8807a68f8fa8 RCX:
0000000000000000
[22328.389046] RDX: 0000000000000001 RSI: ffff8807a68f8fb0 RDI:
ffff8807a68f8fa8
[22328.389047] RBP: ffff8807c09bdca0 R08: 000000000000045e R09:
000000000000e200
[22328.389047] R10: ffffffffa0157d80 R11: ffff8807c09bdde0 R12:
0000000000000001
[22328.389047] R13: 0000000000000000 R14: ffff8807d8493a80 R15:
ffff8807a68f8fb0
[22328.389053] Call Trace:
[22328.389069] [<ffffffffa011af56>] nouveau_fence_wait+0x86/0x1a0 [nouveau]
[22328.389081] [<ffffffffa011ca35>] nouveau_bo_fence_wait+0x15/0x20
[nouveau]
[22328.389084] [<ffffffffa00867c6>] ttm_bo_wait+0x96/0x1a0 [ttm]
[22328.389095] [<ffffffffa0121dac>]
nouveau_gem_ioctl_cpu_prep+0x5c/0xf0 [nouveau]
[22328.389101] [<ffffffffa002cd42>] drm_ioctl+0x502/0x630 [drm]
[22328.389114] [<ffffffffa01180a1>] nouveau_drm_ioctl+0x51/0x90 [nouveau]
I can't find any kind of locking so my question is what ensures that chan is
not set to NULL between nouveau_fence_done() and
nouveau_fence_wait_uevent()? There are just a few opcodes in between but
nothing that pauses nouveau_fence_signal().
Absolutely nothing. :-) Worse still, there's no guarantee that channel isn't freed, but hopefully that is less likely to be an issue.
~Maarten
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