Re: Re: [linus:master] [sched/eevdf] 2227a957e1: BUG:kernel_NULL_pointer_dereference,address

[Oliver Sang]

hi, Abel,

On Wed, Jan 31, 2024 at 08:34:09PM +0800, Abel Wu wrote:
> On 1/30/24 10:09 PM, Oliver Sang Wrote:
> > hi, Abel,
> > 
> > On Tue, Jan 30, 2024 at 06:13:32PM +0800, Abel Wu wrote:
> > > On 1/30/24 3:24 PM, kernel test robot Wrote:
> > > > 
> > > > we found this issue happens in very random way (23 out of 999 runs).
> > > > but keeps clean on parent.
> > > 
> > > Thanks for reporting, I will try to reproduce the issue. Does the 'parent'
> > > mean the same code branch without this commit?
> > 
> > 
> > it just means the parent in git log.
> > 
> > xsang@inn:/c/repo/linux$ git log --oneline --graph 2227a957e1
> > * 2227a957e1d5b sched/eevdf: Sort the rbtree by virtual deadline
> > * 84db47ca7146d sched/numa: Fix mm numa_scan_seq based unconditional scan  <-- parent
> 
> Thanks for clarifying, Oliver. And can you please check the parent's
> dmesg for the log:
> 
> 	pr_err("EEVDF scheduling fail, picking leftmost\n");
> 
> which potentially turns a kernel panic to a message.

yeah, there is. and there are 27 runs have this log from 999 runs, almost same
rate as the crash we reported for 2227a957e1 (which is 23 out of 999 runs).

attached one FYI.

[  600.569585][   T16] EEVDF scheduling fail, picking leftmost
[  600.569900][   T16]
[  600.569902][   T16] ======================================================
[  600.569903][   T16] WARNING: possible circular locking dependency detected
[  600.569905][   T16] 6.7.0-rc1-00005-g84db47ca7146 #1 Tainted: G        W        N
[  600.569907][   T16] ------------------------------------------------------
[  600.569908][   T16] rcu_preempt/16 is trying to acquire lock:
[  600.569910][   T16] c3bb4a48 (console_owner){-.-.}-{0:0}, at: console_lock_spinning_enable+0x27/0x50
[  600.569937][   T16]
[  600.569937][   T16] but task is already holding lock:
[  600.569938][   T16] e75ff0b0 (&rq->__lock){-.-.}-{2:2}, at: rq_lock+0x1f/0xe0
...

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