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
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