linux-kernel - Re: scheduling while atomic in z3fold

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Message-ID: <CAM4kBBJ2jqBKdTPWPZEfuc17yiARMr_NwOSoHL_r0eC9n7UpUQ@mail.gmail.com>
Date:   Mon, 7 Dec 2020 16:21:20 +0100
From:   Vitaly Wool <vitaly.wool@...sulko.com>
To:     Mike Galbraith <efault@....de>
Cc:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Oleksandr Natalenko <oleksandr@...alenko.name>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-rt-users@...r.kernel.org
Subject: Re: scheduling while atomic in z3fold

On Mon, Dec 7, 2020 at 1:34 PM Mike Galbraith <efault@....de> wrote:
>
> On Mon, 2020-12-07 at 12:52 +0100, Vitaly Wool wrote:
> >
> > Thanks. This trace beats me because I don't quite get how this could
> > have happened.
>
> I swear there's a mythical creature loose in there somewhere ;-)
> Everything looks just peachy up to the instant it goes boom, then you
> find in the wreckage that which was most definitely NOT there just a
> few ns ago.
>
> > Hitting write_unlock at line 341 would mean that HANDLES_ORPHANED bit
> > is set but obviously it isn't.
> > Could you please comment out the ".shrink = z3fold_zpool_shrink" line
> > and retry?
>
> Unfortunately, that made zero difference.

Okay, I suggest that you submit the patch that changes read_lock() to
write_lock() in __release_z3fold_page() and I'll ack it then.
I would like to rewrite the code so that write_lock is not necessary
there but I don't want to hold you back and it isn't likely that I'll
complete this today.

Best regards,
   Vitaly