Re: linux-next test error: BUG: using __this_cpu_read() in preemptible code in __mod_memcg_state

[Stephen Rothwell]

Hi Dmitry,

On Sat, 18 Apr 2020 09:04:38 +0200 Dmitry Vyukov <dvyukov@xxxxxxxxxx> wrote:
>
> On Mon, Mar 9, 2020 at 2:27 PM Alex Shi <alex.shi@xxxxxxxxxxxxxxxxx> wrote:
> > å 2020/3/9 äå5:56, Alex Shi åé:  
> > >
> > >
> > > å 2020/3/9 äå5:24, Kirill A. Shutemov åé:  
> > >>> check_preemption_disabled: 3 callbacks suppressed
> > >>> BUG: using __this_cpu_read() in preemptible [00000000] code: syz-fuzzer/9432
> > >>> caller is __mod_memcg_state+0x27/0x1a0 mm/memcontrol.c:689
> > >>> CPU: 1 PID: 9432 Comm: syz-fuzzer Not tainted 5.6.0-rc4-next-20200306-syzkaller #0
> > >>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> > >>> Call Trace:
> > >>>  __dump_stack lib/dump_stack.c:77 [inline]
> > >>>  dump_stack+0x188/0x20d lib/dump_stack.c:118
> > >>>  check_preemption_disabled lib/smp_processor_id.c:47 [inline]
> > >>>  __this_cpu_preempt_check.cold+0x84/0x90 lib/smp_processor_id.c:64
> > >>>  __mod_memcg_state+0x27/0x1a0 mm/memcontrol.c:689
> > >>>  __split_huge_page mm/huge_memory.c:2575 [inline]
> > >>>  split_huge_page_to_list+0x124b/0x3380 mm/huge_memory.c:2862
> > >>>  split_huge_page include/linux/huge_mm.h:167 [inline]  
> > >> It looks like a regression due to c8cba0cc2a80 ("mm/thp: narrow lru
> > >> locking").  
> > >
> > > yes, I guess so.  
> >
> > Yes, it is a stupid mistake to pull out lock for __mod_memcg_state which
> > should be in a lock.
> >
> > revert this patch should be all fine, since ClearPageCompound and page_ref_inc
> > later may related with lru_list valid issue in release_pges.
> >
> >
> > Sorry for the disaster!
> >
> > Alex  
> 
> +linux-next, Stephen for currently open linux-next build/boot failure
> 
> Hi Alex,
> 
> What's the status of this? Was the guilty patch reverted? If so,
> please mark it as invalid for syzbot, otherwise it still shows up as
> open bug.

The patch was removed from Andrew's tree in March and never made it to
Linus' tree.  I can't find how to tell syzbot that the patch went away ...

-- 
Cheers,
Stephen Rothwell

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