* Re: [PATCH -next] fork: silence a false postive warning in __mmdrop
[not found] ` <20200908165043.GD5147@lca.pw>
@ 2020-09-08 17:58 ` peterz
0 siblings, 0 replies; only message in thread
From: peterz @ 2020-09-08 17:58 UTC (permalink / raw)
To: Qian Cai; +Cc: mark.rutland, akpm, linux-kernel, linux-mm, mpe, linuxppc-dev
On Tue, Sep 08, 2020 at 12:50:44PM -0400, Qian Cai wrote:
> > No, you're talking nonsense. We must not free @mm when
> > 'current->active_mm == mm', never.
>
> Yes, you are right. It still trigger this below on powerpc with today's
> linux-next by fuzzing for a while (saw a few times on recent linux-next before
> as well but so far mostly reproducible on powerpc here). Any idea?
If you can reliably reproduce this, the next thing is to trace mm_count
and figure out where it goes side-ways. I suppose we're looking for an
'extra' decrement.
Mark tried this for a while but gave up because he couldn't reliably
reproduce.
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