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Message-ID: <ZsLNtymGVe5wk5vP@chenyu5-mobl2>
Date: Mon, 19 Aug 2024 12:44:39 +0800
From: Chen Yu <yu.c.chen@...el.com>
To: Peter Zijlstra <peterz@...radead.org>, Oliver Sang <oliver.sang@...el.com>
CC: kernel test robot <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 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?
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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