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Revert "drm/i915: Fix context/engine cleanup order"
This reverts commit 1803c03. It seems to blow up on module unload due to a use-after free hitting a BUG_ON with CONFIG_DEBUG_SG. Quoting from Tvrtko's mail: "I've decoded the instructions and it pointed to SG_MAGIC checking: 488b8098010000 mov 0x198(%rax),%rax ba21436587 mov $0x87654321,%edx 488b00 mov (%rax),%rax *** CRASH "Grep showed 0x87654321 is SG_MAGIC, so likely candidate for this code pattern is: static inline struct page *sg_page(struct scatterlist *sg) { BUG_ON(sg->sg_magic != SG_MAGIC); BUG_ON(sg_is_chain(sg)); return (struct page *)((sg)->page_link & ~0x3); } "Which would mean the offender is in intel_logical_ring_cleanup is most likely: ... if (ring->status_page.obj) { kunmap(sg_page(ring->status_page.obj->pages->sgl)); ring->status_page.obj = NULL; } ... "I think that the i915_gem_context_fini will do a final unref on dev_priv->kernel_context and then the ring buff has a copy which is left dangling because: lrc_setup_hardware_status_page(ring, dev_priv->kernel_context->engine[ring->id].state); and: ring->status_page.obj = default_ctx_obj; "Where default_ctx_obj == dev_priv->kernel_context->engine[ring->id].state So indeed looks like the unload ordering is the trigger. In fact it is almost the same fragility wrt/ kernel_context hidden dependency I expressed my worry about in an e-mail yesterday or so. It only shows if CONFIG_DEBUG_SG is set, otherwise it accesses freed memory and probably just survives." This causes serious trouble in our CI system since it took out all gen8+ machines. Not yet clear why this wasn't caught in pre-merge testing. Backtrace from CI, for posterity: [ 163.737836] general protection fault: 0000 [#1] PREEMPT SMP [ 163.737849] Modules linked in: ax88179_178a usbnet mii snd_hda_codec_hdmi snd_hda_codec_realtek snd_hda_codec_generic i915(-) x86_pkg_temp_thermal intel_powerclamp coretemp crct10dif_pclmul crc32_pclmul ghash_clmulni_intel snd_hda_codec snd_hwdep snd_hda_core snd_pcm mei_me mei i2c_hid e1000e ptp pps_core [last unloaded: snd_hda_intel] [ 163.737902] CPU: 0 PID: 5812 Comm: rmmod Tainted: G U W 4.5.0-rc1-gfxbench+ #1 [ 163.737911] Hardware name: System manufacturer System Product Name/Z170M-PLUS, BIOS 0505 11/16/2015 [ 163.737920] task: ffff8800bb99cf80 ti: ffff88022ff2c000 task.ti: ffff88022ff2c000 [ 163.737928] RIP: 0010:[<ffffffffa018f723>] [<ffffffffa018f723>] intel_logical_ring_cleanup+0x83/0x100 [i915] [ 163.737969] RSP: 0018:ffff88022ff2fd30 EFLAGS: 00010282 [ 163.737975] RAX: 6b6b6b6b6b6b6b6b RBX: ffff8800bb2f31b8 RCX: 0000000000000002 [ 163.737982] RDX: 0000000087654321 RSI: 000000000000000d RDI: ffff8800bb2f31f0 [ 163.737989] RBP: ffff88022ff2fd40 R08: 0000000000000000 R09: 0000000000000001 [ 163.737996] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8800bb2f0000 [ 163.738003] R13: ffff8800bb2f8fc8 R14: ffff8800bb285668 R15: 000055af1ae55210 [ 163.738010] FS: 00007f187014b700(0000) GS:ffff88023bc00000(0000) knlGS:0000000000000000 [ 163.738021] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 163.738030] CR2: 0000558f84e4cbc8 CR3: 000000022cd55000 CR4: 00000000003406f0 [ 163.738039] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 163.738048] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 163.738057] Stack: [ 163.738062] ffff8800bb2f31b8 ffff8800bb2f0000 ffff88022ff2fd70 ffffffffa0180414 [ 163.738079] ffff8800bb2f0000 ffff8800bb285668 ffff8800bb2856c8 ffffffffa0242460 [ 163.738094] ffff88022ff2fd98 ffffffffa0202d30 ffff8800bb285668 ffff8800bb285668 [ 163.738109] Call Trace: [ 163.738140] [<ffffffffa0180414>] i915_gem_cleanup_engines+0x34/0x60 [i915] [ 163.738185] [<ffffffffa0202d30>] i915_driver_unload+0x150/0x270 [i915] [ 163.738198] [<ffffffff815100f4>] drm_dev_unregister+0x24/0xa0 [ 163.738208] [<ffffffff815106ce>] drm_put_dev+0x1e/0x60 [ 163.738225] [<ffffffffa01412a0>] i915_pci_remove+0x10/0x20 [i915] [ 163.738237] [<ffffffff8143d9b4>] pci_device_remove+0x34/0xb0 [ 163.738249] [<ffffffff81533d15>] __device_release_driver+0x95/0x140 [ 163.738259] [<ffffffff81533eb6>] driver_detach+0xb6/0xc0 [ 163.738268] [<ffffffff81532de3>] bus_remove_driver+0x53/0xd0 [ 163.738278] [<ffffffff815348d7>] driver_unregister+0x27/0x50 [ 163.738289] [<ffffffff8143ca15>] pci_unregister_driver+0x25/0x70 [ 163.738299] [<ffffffff81511de4>] drm_pci_exit+0x74/0x90 [ 163.738337] [<ffffffffa02034a9>] i915_exit+0x20/0x1a5 [i915] [ 163.738349] [<ffffffff8110400f>] SyS_delete_module+0x18f/0x1f0 [ 163.738361] [<ffffffff817b8a9b>] entry_SYSCALL_64_fastpath+0x16/0x73 [ 163.738370] Code: ff d0 48 89 df e8 de a1 fd ff 48 8d 7b 38 e8 25 ab fd ff 48 8b 83 90 00 00 00 48 85 c0 74 25 48 8b 80 98 01 00 00 ba 21 43 65 87 <48> 8b 00 48 39 10 75 3c f6 40 08 01 75 38 48 c7 83 90 00 00 00 [ 163.738459] RIP [<ffffffffa018f723>] intel_logical_ring_cleanup+0x83/0x100 [i915] [ 163.738498] RSP <ffff88022ff2fd30> [ 163.738507] ---[ end trace 68f69ce4740fa44f ]--- Cc: Nick Hoath <[email protected]> Cc: Dave Gordon <[email protected]> Cc: Chris Wilson <[email protected]> Cc: Tvrtko Ursulin <[email protected]> Cc: Mika Kuoppala <[email protected]> Reviewed-by: Mika Kuoppala <[email protected]> Tested-by: Mika Kuoppala <[email protected]> Signed-off-by: Daniel Vetter <[email protected]>
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