linux-kernel - Re: [PATCH 1/2] ARC: show_regs: avoid page allocator

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

On 12/20/18 5:30 AM, Tetsuo Handa wrote:
>> | Stack Trace:
>> |  arc_unwind_core+0xcc/0x100
>> |  ___might_sleep+0x17a/0x190
>> |  mmput+0x16/0xb8
> Then, does mmput_async() help?
>

It helps, but then we get the next one (w/o my patch 2/2)

BUG: sleeping function called from invalid context at kernel/locking/rwsem.c:23
in_atomic(): 1, irqs_disabled(): 0, pid: 69, name: segv-null-ptr
no locks held by segv-null-ptr/69.
CPU: 0 PID: 69 Comm: segv-null-ptr Not tainted 4.18.0+ #72

Stack Trace:
  arc_unwind_core+0xcc/0x100
  ___might_sleep+0x17a/0x190
  down_read+0x18/0x38
  show_regs+0x102/0x310
  get_signal+0x5ee/0x610
  do_signal+0x2c/0x218
  resume_user_mode_begin+0x90/0xd8
    @off 0x103d4 in [/segv-null-pt