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[198.54.129.52]) by smtp.gmail.com with ESMTPSA id x18sm4147758pfi.22.2020.04.14.07.35.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 14 Apr 2020 07:35:22 -0700 (PDT) Date: Tue, 14 Apr 2020 07:35:18 -0700 From: Sultan Alsawaf To: Chris Wilson Cc: Greg KH , stable@vger.kernel.org, Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , David Airlie , Daniel Vetter , intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org Subject: Re: [PATCH v2] drm/i915: Fix ref->mutex deadlock in i915_active_wait() Message-ID: <20200414143518.GA2082@sultan-box.localdomain> References: <20200407065210.GA263852@kroah.com> <20200407071809.3148-1-sultan@kerneltoast.com> <20200410090838.GD1691838@kroah.com> <20200410141738.GB2025@sultan-box.localdomain> <20200411113957.GB2606747@kroah.com> <158685210730.16269.15932754047962572236@build.alporthouse.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <158685210730.16269.15932754047962572236@build.alporthouse.com> Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Tue, Apr 14, 2020 at 09:15:07AM +0100, Chris Wilson wrote: > The patch does not fix a deadlock. Greg, this patch is not a backport of > a bugfix, why is it in stable? > -Chris Here's the deadlock this supposedly doesn't fix: INFO: task kswapd0:178 blocked for more than 122 seconds. Tainted: G U 5.4.28-00014-gd1e04f91d2c5 #4 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. kswapd0 D 0 178 2 0x80004000 Call Trace: ? __schedule+0x2f3/0x750 schedule+0x39/0xa0 schedule_preempt_disabled+0xa/0x10 __mutex_lock.isra.0+0x19b/0x500 ? i915_request_wait+0x25b/0x370 active_retire+0x26/0x30 i915_active_wait+0xa3/0x1a0 i915_vma_unbind+0xe2/0x1c0 i915_gem_object_unbind+0x111/0x140 i915_gem_shrink+0x21b/0x530 i915_gem_shrinker_scan+0xfd/0x120 do_shrink_slab+0x154/0x2c0 shrink_slab+0xd0/0x2f0 shrink_node+0xdf/0x420 balance_pgdat+0x2e3/0x540 kswapd+0x200/0x3c0 ? __wake_up_common_lock+0xc0/0xc0 kthread+0xfb/0x130 ? balance_pgdat+0x540/0x540 ? __kthread_parkme+0x60/0x60 ret_from_fork+0x1f/0x40 INFO: task kworker/u32:5:222 blocked for more than 122 seconds. Tainted: G U 5.4.28-00014-gd1e04f91d2c5 #4 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. kworker/u32:5 D 0 222 2 0x80004000 Workqueue: i915 idle_work_handler Call Trace: ? __schedule+0x2f3/0x750 schedule+0x39/0xa0 schedule_preempt_disabled+0xa/0x10 __mutex_lock.isra.0+0x19b/0x500 idle_work_handler+0x34/0x120 process_one_work+0x1ea/0x3a0 worker_thread+0x4d/0x3f0 kthread+0xfb/0x130 ? process_one_work+0x3a0/0x3a0 ? __kthread_parkme+0x60/0x60 ret_from_fork+0x1f/0x40 INFO: task mpv:1535 blocked for more than 122 seconds. Tainted: G U 5.4.28-00014-gd1e04f91d2c5 #4 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. mpv D 0 1535 1 0x00000000 Call Trace: ? __schedule+0x2f3/0x750 schedule+0x39/0xa0 schedule_preempt_disabled+0xa/0x10 __mutex_lock.isra.0+0x19b/0x500 __i915_gem_free_objects+0x68/0x190 i915_gem_create_ioctl+0x18/0x30 ? i915_gem_dumb_create+0xa0/0xa0 drm_ioctl_kernel+0xb2/0x100 drm_ioctl+0x209/0x360 ? i915_gem_dumb_create+0xa0/0xa0 do_vfs_ioctl+0x43f/0x6c0 ksys_ioctl+0x5e/0x90 __x64_sys_ioctl+0x16/0x20 do_syscall_64+0x4e/0x140 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x7fb49f1b32eb Code: Bad RIP value. RSP: 002b:00007ffef9eb0948 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007ffef9eb09c0 RCX: 00007fb49f1b32eb RDX: 00007ffef9eb09c0 RSI: 00000000c010645b RDI: 0000000000000008 RBP: 00000000c010645b R08: 000055fdb80c1370 R09: 000055fdb80c14e0 R10: 0000000000000000 R11: 0000000000000246 R12: 00007fb4781e56b0 R13: 0000000000000008 R14: 00007fb4781e5560 R15: 00007fb4781e56b0 INFO: task kswapd0:178 blocked for more than 245 seconds. Tainted: G U 5.4.28-00014-gd1e04f91d2c5 #4 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. kswapd0 D 0 178 2 0x80004000 Call Trace: ? __schedule+0x2f3/0x750 schedule+0x39/0xa0 schedule_preempt_disabled+0xa/0x10 __mutex_lock.isra.0+0x19b/0x500 ? i915_request_wait+0x25b/0x370 active_retire+0x26/0x30 i915_active_wait+0xa3/0x1a0 i915_vma_unbind+0xe2/0x1c0 i915_gem_object_unbind+0x111/0x140 i915_gem_shrink+0x21b/0x530 i915_gem_shrinker_scan+0xfd/0x120 do_shrink_slab+0x154/0x2c0 shrink_slab+0xd0/0x2f0 shrink_node+0xdf/0x420 balance_pgdat+0x2e3/0x540 kswapd+0x200/0x3c0 ? __wake_up_common_lock+0xc0/0xc0 kthread+0xfb/0x130 ? balance_pgdat+0x540/0x540 ? __kthread_parkme+0x60/0x60 ret_from_fork+0x1f/0x40 INFO: task kworker/u32:5:222 blocked for more than 245 seconds. Tainted: G U 5.4.28-00014-gd1e04f91d2c5 #4 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. kworker/u32:5 D 0 222 2 0x80004000 Workqueue: i915 idle_work_handler Call Trace: ? __schedule+0x2f3/0x750 schedule+0x39/0xa0 schedule_preempt_disabled+0xa/0x10 __mutex_lock.isra.0+0x19b/0x500 idle_work_handler+0x34/0x120 process_one_work+0x1ea/0x3a0 worker_thread+0x4d/0x3f0 kthread+0xfb/0x130 ? process_one_work+0x3a0/0x3a0 ? __kthread_parkme+0x60/0x60 ret_from_fork+0x1f/0x40 INFO: task mpv:1535 blocked for more than 245 seconds. Tainted: G U 5.4.28-00014-gd1e04f91d2c5 #4 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. mpv D 0 1535 1 0x00000000 Call Trace: ? __schedule+0x2f3/0x750 schedule+0x39/0xa0 schedule_preempt_disabled+0xa/0x10 __mutex_lock.isra.0+0x19b/0x500 __i915_gem_free_objects+0x68/0x190 i915_gem_create_ioctl+0x18/0x30 ? i915_gem_dumb_create+0xa0/0xa0 drm_ioctl_kernel+0xb2/0x100 drm_ioctl+0x209/0x360 ? i915_gem_dumb_create+0xa0/0xa0 do_vfs_ioctl+0x43f/0x6c0 ksys_ioctl+0x5e/0x90 __x64_sys_ioctl+0x16/0x20 do_syscall_64+0x4e/0x140 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x7fb49f1b32eb Code: Bad RIP value. RSP: 002b:00007ffef9eb0948 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007ffef9eb09c0 RCX: 00007fb49f1b32eb RDX: 00007ffef9eb09c0 RSI: 00000000c010645b RDI: 0000000000000008 RBP: 00000000c010645b R08: 000055fdb80c1370 R09: 000055fdb80c14e0 R10: 0000000000000000 R11: 0000000000000246 R12: 00007fb4781e56b0 R13: 0000000000000008 R14: 00007fb4781e5560 R15: 00007fb4781e56b0 Dead inside the shrinker, and very easy to reproduce. Sultan