linux-kernel - Re: kernel BUG at kernel/sched/core.c:3490!

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Date:   Sat, 12 Jan 2019 14:24:24 +0530
From:   "Kohli, Gaurav" <gkohli@...eaurora.org>
To:     Qian Cai <cai@....pw>, Oleg Nesterov <oleg@...hat.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        linux kernel <linux-kernel@...r.kernel.org>
Subject: Re: kernel BUG at kernel/sched/core.c:3490!

HI Peter, Oleg,

as per flag and state this seems to be possible only from below code:
XXX: 0 1 0x40844c
PF_NOFREEZE
PF_RANDOMIZE
PF_SIGNALED
PF_FORKNOEXEC
PF_EXITING
PF_EXITPIDONE

above state shows do_exit runs properely and  if somehow after parked 
stated , TASK_WAKEKILL got set and signal_pending_state returns 1 in 
below case:

  switch_count = &prev->nivcsw;
         if (!preempt && prev->state) {
                 if (unlikely(signal_pending_state(prev->state, prev))) {
                         prev->state = TASK_RUNNING;
                 } else {
                         deactivate_task(rq, prev, DEQUEUE_SLEEP | 
DEQUEUE_NOCLOCK);

Regards
Gaurav


On 1/11/2019 9:47 PM, Qian Cai wrote:
> On Fri, 2019-01-11 at 16:07 +0530, Kohli, Gaurav wrote:
>>
>> On 1/7/2019 11:26 PM, Oleg Nesterov wrote:
>>> pr_crit("XXX: %ld %d\n", current->state, current->on_rq);
>>
>> Can we also add flags, this may help to know the path of problem:
>>
>>    pr_crit("XXX: %ld %d 0x%x\n", current->state, current->on_rq, 	
>> current->flags);
>>
> 
> XXX: 0 1 0x40844c
> 

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