Messages in this thread Patch in this message | | | From | Kuyo Chang (張建文) <> | Subject | Re: [PATCH 1/1] sched/core: Fix stuck on completion for affine_move_task() when stopper disable | Date | Wed, 27 Sep 2023 15:57:35 +0000 |
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On Wed, 2023-09-27 at 10:08 +0200, Peter Zijlstra wrote: > > External email : Please do not click links or open attachments until > you have verified the sender or the content. > On Wed, Sep 27, 2023 at 11:34:28AM +0800, Kuyo Chang wrote: > > From: kuyo chang <kuyo.chang@mediatek.com> > > > > [Syndrome] hung detect shows below warning msg > > [ 4320.666557] [ T56] khungtaskd: [name:hung_task&]INFO: task > stressapptest:17803 blocked for more than 3600 seconds. > > [ 4320.666589] [ T56] khungtaskd: > [name:core&]task:stressapptest state:D stack:0 pid:17803 > ppid:17579 flags:0x04000008 > > [ 4320.666601] [ T56] khungtaskd: Call trace: > > [ 4320.666607] [ T56] khungtaskd: __switch_to+0x17c/0x338 > > [ 4320.666642] [ T56] khungtaskd: __schedule+0x54c/0x8ec > > [ 4320.666651] [ T56] khungtaskd: schedule+0x74/0xd4 > > [ 4320.666656] [ T56] khungtaskd: schedule_timeout+0x34/0x108 > > [ 4320.666672] [ T56] khungtaskd: do_wait_for_common+0xe0/0x154 > > [ 4320.666678] [ T56] khungtaskd: wait_for_completion+0x44/0x58 > > [ 4320.666681] [ T56] > khungtaskd: __set_cpus_allowed_ptr_locked+0x344/0x730 > > [ 4320.666702] [ T56] > khungtaskd: __sched_setaffinity+0x118/0x160 > > [ 4320.666709] [ T56] khungtaskd: sched_setaffinity+0x10c/0x248 > > [ 4320.666715] [ T56] > khungtaskd: __arm64_sys_sched_setaffinity+0x15c/0x1c0 > > [ 4320.666719] [ T56] khungtaskd: invoke_syscall+0x3c/0xf8 > > [ 4320.666743] [ T56] khungtaskd: el0_svc_common+0xb0/0xe8 > > [ 4320.666749] [ T56] khungtaskd: do_el0_svc+0x28/0xa8 > > [ 4320.666755] [ T56] khungtaskd: el0_svc+0x28/0x9c > > [ 4320.666761] [ T56] khungtaskd: el0t_64_sync_handler+0x7c/0xe4 > > [ 4320.666766] [ T56] khungtaskd: el0t_64_sync+0x18c/0x190 > > > > [Analysis] > > > > After add some debug footprint massage, this issue happened at > stopper > > disable case. > > It cannot exec migration_cpu_stop fun to complete migration. > > This will cause stuck on wait_for_completion. > > How did you get in this situation? >
This issue occurs at CPU hotplug/set_affinity stress test. The reproduce ratio is very low(about once a week).
So I add/record some debug message to snapshot the task status while it stuck on wait_for_completion.
Below is the snapshot status while issue happened:
cpu_active_mask is 0xFC new_mask is 0x8 pending->arg.dest_cpu is 0x3 task_on_cpu(rq,p) is 1 task_cpu is 0x2 p__state = TASK_RUNNING flag is SCA_CHACK|SCA_USER stop_one_cpu_nowait(stopper->enabled) return value is false.
I also record the footprint at migration_cpu_stop. It shows the migration_cpu_stop is not execute.
> > Signed-off-by: kuyo chang <kuyo.chang@mediatek.com> > > --- > > kernel/sched/core.c | 5 +++-- > > 1 file changed, 3 insertions(+), 2 deletions(-) > > > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > > index 1dc0b0287e30..98c217a1caa0 100644 > > --- a/kernel/sched/core.c > > +++ b/kernel/sched/core.c > > @@ -3041,8 +3041,9 @@ static int affine_move_task(struct rq *rq, > struct task_struct *p, struct rq_flag > > task_rq_unlock(rq, p, rf); > > > > if (!stop_pending) { > > -stop_one_cpu_nowait(cpu_of(rq), migration_cpu_stop, > > - &pending->arg, &pending->stop_work); > > +if (!stop_one_cpu_nowait(cpu_of(rq), migration_cpu_stop, > > + &pending->arg, &pending->stop_work)) > > +return -ENOENT; > > And -ENOENT is the right return code for when the target CPU is not > available? > > I suspect you're missing more than halp the picture and this is a > band-aid solution at best. Please try harder. >
I think -ENOENT means stopper is not execute? Perhaps the error code is abused, or could you kindly give me some suggestions?
Thanks, Kuyo
> > } > > > > if (flags & SCA_MIGRATE_ENABLE) > > -- > > 2.18.0 > >
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