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Message-ID: <4CD91A07.1060308@vmware.com> Date: Tue, 09 Nov 2010 10:53:11 +0100 From: Thomas Hellstrom <thellstrom@...are.com> To: Markus Trippelsdorf <markus@...ppelsdorf.de> CC: Jerome Glisse <j.glisse@...il.com>, "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "airlied@...ux.ie" <airlied@...ux.ie>, Michel Danzer <daenzer@...are.com> Subject: Re: Radeon RS780 - BUG: unable to handle kernel NULL pointer dereference On 11/09/2010 10:29 AM, Markus Trippelsdorf wrote: > On Mon, Nov 08, 2010 at 11:29:16PM +0100, Thomas Hellstrom wrote: > >> On 11/08/2010 09:53 PM, Jerome Glisse wrote: >> >>> On Mon, Nov 8, 2010 at 2:02 PM, Markus Trippelsdorf >>> <markus@...ppelsdorf.de> wrote: >>> >>>> On Mon, Nov 08, 2010 at 07:43:02PM +0100, Markus Trippelsdorf wrote: >>>> >>>>> On Mon, Nov 08, 2010 at 06:07:37PM +0100, Markus Trippelsdorf wrote: >>>>> >>>>>> On Mon, Nov 08, 2010 at 06:02:21PM +0100, Markus Trippelsdorf wrote: >>>>>> >>>>>>> I can trigger a kernel crash on my system by simply loading this png >>>>>>> image with firefox: >>>>>>> http://mediaarchive.cern.ch/MediaArchive/Photo/Public/2010/1011251/1011251_01/1011251_01-A4-at-144-dpi.jpg >>>>>>> >>>>>> Sorry the above link is wrong, this is the right one (that triggers the >>>>>> crash): >>>>>> http://cdsweb.cern.ch/record/1305179/files/HI-150431-630470-huge.png >>>>>> >>>>> I triggered it a few more times and took the attached picture. >>>>> It points to the BUG() call at drivers/gpu/drm/ttm/ttm_bo.c:1628 . >>>>> (Sorry for the bad picture quality) >>>>> >>>> And here the same BUG in plaintext (should be a bit easier to read): >>>> >>>> Nov 8 19:28:23 arch kernel: ------------[ cut here ]------------ >>>> Nov 8 19:28:23 arch kernel: kernel BUG at drivers/gpu/drm/ttm/ttm_bo.c:1628! >>>> >>>> >>> Thomas this bug seems to point to a case where we endup trying adding >>> an entry to >>> same offset in the rb tree for addr_space_mm. After reviewing >>> carefully the locking >>> around the rb tree modification& addr_space_mm i am fairly confident >>> that no race can >>> occur. Would you have any idea on what might go wrong here ? I guess i would >>> ultimately need to dump mm& rb tree state when BUG get trigger to try >>> to understand >>> states of things. >>> >> I agree there shouldn't be a race in this case. >> The locking around these operations is simple and straightforward. >> >> So this IMHO should either be a memory corruption or a bug in the >> range manager. I've never seen this BUG trigger before. Dumping mm / >> rb tree contents or bisecting should probably find the culprit. >> > OK I've found the buggy commit by bisection: > > e376573f7267390f4e1bdc552564b6fb913bce76 is the first bad commit > commit e376573f7267390f4e1bdc552564b6fb913bce76 > Author: Michel Dänzer<daenzer@...are.com> > Date: Thu Jul 8 12:43:28 2010 +1000 > > drm/radeon: fall back to GTT if bo creation/validation in VRAM fails. > > This fixes a problem where on low VRAM cards we'd run out of space for validation. > > [airlied: Tested on my M7, Thinkpad T42, compiz works with no problems.] > > Signed-off-by: Michel Dänzer<daenzer@...are.com> > Cc: stable@...nel.org > Signed-off-by: Dave Airlie<airlied@...hat.com> > > Please note that this is an old commit from 2.6.36-rc. When I revert it the > kernel no longer crashes. Instead I see the following in my dmesg: > > Hmm, so this sounds like something in the Radeon eviction error path is causing corruption. I had a similar problem with vmwgfx, when I tried to unref a BO _after_ ttm_bo_init() failed. ttm_bo_init() is really supposed to call unref itself for various reasons, so calling unref() or kfree() after a failed ttm_bo_init() will cause corruption. In any case, the error below also suggests something is a bit fragile in the Radeon driver: First, an accelerated eviction may fail, like in the message below, but then there must always be a backup plan, like unaccelerated eviction to system. On BO creation, there are a number of placement strategies, but if all else fails, it should be possible to initially place the BO in system memory. Second, If bo validation fails during a command submission, due to insufficient VRAM / TT, then the driver should retry the complete validation cycle after first blocking all other validators and then evicting everything not pinned, to avoid failures due to fragmentation. /Thomas > [TTM] Failed to find memory space for buffer 0xffff880113e10e48 eviction. > [TTM] No space for ffff880113e10e48 (25650 pages, 102600K, 100M) > [TTM] placement[0]=0x00070002 (1) > [TTM] has_type: 1 > [TTM] use_type: 1 > [TTM] flags: 0x0000000A > [TTM] gpu_offset: 0xA0000000 > [TTM] size: 131072 > [TTM] available_caching: 0x00070000 > [TTM] default_caching: 0x00010000 > [TTM] 0x00000000-0x00000001: 1: used > [TTM] 0x00000001-0x00000011: 16: used > [TTM] 0x00000011-0x00000111: 256: used > [TTM] 0x00000111-0x00000211: 256: used > [TTM] 0x00000211-0x00000248: 55: free > [TTM] 0x00000248-0x0000024c: 4: used > [TTM] 0x0000024c-0x00001976: 5930: free > [TTM] 0x00001976-0x000021aa: 2100: used > [TTM] 0x000021aa-0x0000285f: 1717: free > [TTM] 0x0000285f-0x00002860: 1: used > [TTM] 0x00002860-0x00002873: 19: free > [TTM] 0x00002873-0x000029b3: 320: used > [TTM] 0x000029b3-0x00020000: 120397: free > [TTM] total: 131072, used 2954 free 128118 > [drm:radeon_cs_ioctl] *ERROR* Failed to parse relocation -12! > radeon 0000:01:05.0: object_init failed for (117555200, 0x00000004) > [drm:radeon_gem_object_create] *ERROR* Failed to allocate GEM object (117555200, 4, 4096, -12) > radeon 0000:01:05.0: object_init failed for (117555200, 0x00000004) > [drm:radeon_gem_object_create] *ERROR* Failed to allocate GEM object (117555200, 4, 4096, -12) > radeon 0000:01:05.0: object_init failed for (117555200, 0x00000004) > [drm:radeon_gem_object_create] *ERROR* Failed to allocate GEM object (117555200, 4, 4096, -12) > radeon 0000:01:05.0: object_init failed for (117555200, 0x00000004) > [drm:radeon_gem_object_create] *ERROR* Failed to allocate GEM object (117555200, 4, 4096, -12) > radeon 0000:01:05.0: object_init failed for (117555200, 0x00000004) > ... > > And the following in the xorg log buffer: > > Failed to alloc memory > Failed to allocat: > size: : 117555200 bytes > alignment : 0 bytes > domains : 4 > ... > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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