Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 678476053B
Subject: Re: kernel BUG at kernel/sched/core.c:3490!
To:     Qian Cai <cai@lca.pw>, Oleg Nesterov <oleg@redhat.com>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        linux kernel <linux-kernel@vger.kernel.org>
References: <ba9c5ad8-d78c-904d-0430-a67d8e3ea729@lca.pw>
 <20190107135215.GG14122@hirez.programming.kicks-ass.net>
 <46089f1c-ad72-c96c-2f35-c2f60e726462@lca.pw>
 <20190107175644.GB7636@redhat.com>
 <3a6d8f4c-d7ed-e888-601b-a379efec306a@codeaurora.org>
 <1547223444.6911.19.camel@lca.pw>
From:   "Kohli, Gaurav" <gkohli@codeaurora.org>
Message-ID: <5a65a014-9013-cfbd-48a9-67199d33e719@codeaurora.org>
Date:   Sat, 12 Jan 2019 14:24:24 +0530
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:60.0) Gecko/20100101
 Thunderbird/60.4.0
MIME-Version: 1.0
In-Reply-To: <1547223444.6911.19.camel@lca.pw>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Language: en-US
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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
> 

-- 
Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center, 
Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project.