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From: Vineet Gupta <vineet.gupta1@synopsys.com>
Subject: Re: [PATCH 1/2] ARC: show_regs: avoid page allocator
Date: Thu, 20 Dec 2018 18:43:08 +0000
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To: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>, Eugeniy Paltsev <eugeniy.paltsev@synopsys.com>, "linux-snps-arc@lists.infradead.org" <linux-snps-arc@lists.infradead.org>
Cc: "linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>, "linux-mm@kvack.org" <linux-mm@kvack.org>, "peterz@infradead.org" <peterz@infradead.org>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, Michal Hocko <mhocko@kernel.org>

On 12/20/18 5:30 AM, Tetsuo Handa wrote:=0A=
>> | Stack Trace:=0A=
>> |  arc_unwind_core+0xcc/0x100=0A=
>> |  ___might_sleep+0x17a/0x190=0A=
>> |  mmput+0x16/0xb8=0A=
> Then, does mmput_async() help?=0A=
>=0A=
=0A=
It helps, but then we get the next one (w/o my patch 2/2)=0A=
=0A=
BUG: sleeping function called from invalid context at kernel/locking/rwsem.=
c:23=0A=
in_atomic(): 1, irqs_disabled(): 0, pid: 69, name: segv-null-ptr=0A=
no locks held by segv-null-ptr/69.=0A=
CPU: 0 PID: 69 Comm: segv-null-ptr Not tainted 4.18.0+ #72=0A=
=0A=
Stack Trace:=0A=
  arc_unwind_core+0xcc/0x100=0A=
  ___might_sleep+0x17a/0x190=0A=
  down_read+0x18/0x38=0A=
  show_regs+0x102/0x310=0A=
  get_signal+0x5ee/0x610=0A=
  do_signal+0x2c/0x218=0A=
  resume_user_mode_begin+0x90/0xd8=0A=
    @off 0x103d4 in [/segv-null-pt=0A=