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Message-ID: <20240822154923.GB17097@noisy.programming.kicks-ass.net>
Date: Thu, 22 Aug 2024 17:49:23 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Chen Yu <yu.c.chen@...el.com>
Cc: Oliver Sang <oliver.sang@...el.com>, oe-lkp@...ts.linux.dev,
lkp@...el.com, linux-kernel@...r.kernel.org,
aubrey.li@...ux.intel.com
Subject: Re: [peterz-queue:sched/core] [sched/fair] 420356c350:
WARNING:at_kernel/sched/core.c:#__might_sleep
On Mon, Aug 19, 2024 at 12:44:39PM +0800, Chen Yu wrote:
> On 2024-08-17 at 11:33:29 +0200, Peter Zijlstra wrote:
> > On Fri, Aug 16, 2024 at 05:15:12PM +0800, kernel test robot wrote:
> > > kernel test robot noticed "WARNING:at_kernel/sched/core.c:#__might_sleep" on:
> > >
> > > commit: 420356c3504091f0f6021974389df7c58f365dad ("sched/fair: Implement delayed dequeue")
> > > https://git.kernel.org/cgit/linux/kernel/git/peterz/queue.git sched/core
> >
> > > [ 86.252370][ T674] ------------[ cut here ]------------
> > > [ 86.252945][ T674] do not call blocking ops when !TASK_RUNNING; state=1 set at kthread_worker_fn (kernel/kthread.c:?)
> > > [ 86.254001][ T674] WARNING: CPU: 1 PID: 674 at kernel/sched/core.c:8469 __might_sleep (kernel/sched/core.c:8465)
> >
> > > [ 86.283398][ T674] ? handle_bug (arch/x86/kernel/traps.c:239)
> > > [ 86.283995][ T674] ? exc_invalid_op (arch/x86/kernel/traps.c:260)
> > > [ 86.284787][ T674] ? asm_exc_invalid_op (arch/x86/include/asm/idtentry.h:621)
> > > [ 86.285682][ T674] ? __might_sleep (kernel/sched/core.c:8465)
> > > [ 86.286380][ T674] ? __might_sleep (kernel/sched/core.c:8465)
> > > [ 86.287116][ T674] kthread_worker_fn (include/linux/kernel.h:73 include/linux/freezer.h:53 kernel/kthread.c:851)
> > > [ 86.287701][ T674] ? kthread_worker_fn (kernel/kthread.c:?)
> > > [ 86.288138][ T674] kthread (kernel/kthread.c:391)
> > > [ 86.288482][ T674] ? __cfi_kthread_worker_fn (kernel/kthread.c:803)
> > > [ 86.288951][ T674] ? __cfi_kthread (kernel/kthread.c:342)
> > > [ 86.289560][ T674] ret_from_fork (arch/x86/kernel/process.c:153)
> > > [ 86.290162][ T674] ? __cfi_kthread (kernel/kthread.c:342)
> > > [ 86.291465][ T674] ret_from_fork_asm (arch/x86/entry/entry_64.S:254)
> >
> > AFAICT this is a pre-existing issue. Notably that all transcribes to:
> >
> > kthread_worker_fn()
> > ...
> > repeat:
> > set_current_state(TASK_INTERRUPTIBLE);
> > ...
> > if (work) { // false
> > __set_current_state(TASK_RUNNING);
> > ...
> > } else if (!freezing(current)) // false -- we are freezing
> > schedule();
> >
> > // so state really is still TASK_INTERRUPTIBLE here
> > try_to_freeze()
> > might_sleep() <--- boom, per the above.
> >
>
> Would the following fix make sense?
Yeah, that looks fine. Could you write it up as a proper patch please?
>
> diff --git a/kernel/kthread.c b/kernel/kthread.c
> index f7be976ff88a..09850b2109c9 100644
> --- a/kernel/kthread.c
> +++ b/kernel/kthread.c
> @@ -848,6 +848,12 @@ int kthread_worker_fn(void *worker_ptr)
> } else if (!freezing(current))
> schedule();
>
> + /*
> + * Explictly set the running state in case we are being frozen
> + * and skip the schedule() above. try_to_freeze() expects the
> + * current task to be in running state.
> + */
> + __set_current_state(TASK_RUNNING);
> try_to_freeze();
> cond_resched();
> goto repeat;
> --
> 2.25.1
>
> Hi Oliver,
> Could you please help check if above change would make the warning go away?
>
> thanks,
> Chenyu
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