Messages in this thread | | | Subject | Re: [PATCH 1/1] sched/debug: fix potential deadlock when write to sched_features | From | Dietmar Eggemann <> | Date | Tue, 31 Jul 2018 13:38:07 +0200 |
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On 07/31/2018 12:34 PM, Peter Zijlstra wrote: > > Leaving a lot of quoted crud for Viresh.. > > On Tue, Jul 31, 2018 at 06:22:19PM +0900, jiada_wang@mentor.com wrote: >> From: Jiada Wang <jiada_wang@mentor.com> >> >> Following lockdep report can be triggered by write to >> /sys/kernel/debug/sched_features > > Only if you're using this dt_cpufreq thing of course.. I wonder why this > hasn't been reported before. >
[...]
> > I don't much care for all the _cpuslocked renaming done, but otherwise I > suppose this is the easiest fix. > > Note however that this doesn't apply, you're missing that match_string() > patch. Please use tip/sched/core or something.
With the patch tweaked onto tip/sched/core.
w/o the patch:
root@h960:~# echo NO_LB_BIAS > /sys/kernel/debug/sched_features [ 293.052451] [ 293.053978] ====================================================== [ 293.060166] WARNING: possible circular locking dependency detected [ 293.066358] 4.18.0-rc5-00064-gae48698275b3 #1 Tainted: G S [ 293.073153] ------------------------------------------------------ [ 293.079340] bash/3490 is trying to acquire lock: [ 293.083966] 00000000155b9437 (cpu_hotplug_lock.rw_sem){++++}, at: static_key_disable+0x1c/0x38 [ 293.092620] [ 293.092620] but task is already holding lock: [ 293.098459] 0000000084a95e1c (&sb->s_type->i_mutex_key#3){+.+.}, at: sched_feat_write+0xc4/0x1e0 [ 293.107277] [ 293.107277] which lock already depends on the new lock. ...
w/ the patch:
root@h960:~# echo NO_LB_BIAS > /sys/kernel/debug/sched_features root@h960:~#
Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
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