linux-kernel - Re: [PATCH V2] mm, memory_failure: don't send BUS_MCEERR

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Date:   Mon, 1 Jun 2020 03:11:25 +0000
From:   HORIGUCHI NAOYA(堀口　直也) 
        <naoya.horiguchi@....com>
To:     Pankaj Gupta <pankaj.gupta.linux@...il.com>
CC:     Wetp Zhang <wetp.zy@...ux.alibaba.com>,
        "n-horiguchi@...jp.nec.com" <n-horiguchi@...jp.nec.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V2] mm, memory_failure: don't send BUS_MCEERR_AO for
 action required error

On Sat, May 30, 2020 at 09:08:43AM +0200, Pankaj Gupta wrote:
> > Some processes dont't want to be killed early, but in "Action Required"
> > case, those also may be killed by BUS_MCEERR_AO when sharing memory
> > with other which is accessing the fail memory.
> > And sending SIGBUS with BUS_MCEERR_AO for action required error is
> > strange, so ignore the non-current processes here.
> >
> > Suggested-by: Naoya Horiguchi <naoya.horiguchi@....com>
> > Signed-off-by: Wetp Zhang <wetp.zy@...ux.alibaba.com>
> > ---
> >  mm/memory-failure.c | 15 +++++++++------
> >  1 file changed, 9 insertions(+), 6 deletions(-)
> >
> > diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> > index a96364be8ab4..dd3862fcf2e9 100644
> > --- a/mm/memory-failure.c
> > +++ b/mm/memory-failure.c
> > @@ -210,14 +210,17 @@ static int kill_proc(struct to_kill *tk, unsigned long pfn, int flags)
> >  {
> >         struct task_struct *t = tk->tsk;
> >         short addr_lsb = tk->size_shift;
> > -       int ret;
> > +       int ret = 0;
> >
> > -       pr_err("Memory failure: %#lx: Sending SIGBUS to %s:%d due to hardware memory corruption\n",
> > -               pfn, t->comm, t->pid);
> > +       if ((t->mm == current->mm) || !(flags & MF_ACTION_REQUIRED))
> > +               pr_err("Memory failure: %#lx: Sending SIGBUS to %s:%d due to hardware memory corruption\n",
> > +                       pfn, t->comm, t->pid);
> 
> Maybe we can generalize the message condition for better readability.
> Thought a bit but did not get any other idea.

This odd condition might imply that we could have better fix in
task_early_kill(), but that should come after fixing priority issue of
early-kill flag, so let's go with this fix for now.

> >
> > -       if ((flags & MF_ACTION_REQUIRED) && t->mm == current->mm) {
> > -               ret = force_sig_mceerr(BUS_MCEERR_AR, (void __user *)tk->addr,
> > -                                      addr_lsb);
> > +       if (flags & MF_ACTION_REQUIRED) {
> > +               if (t->mm == current->mm)
> > +                       ret = force_sig_mceerr(BUS_MCEERR_AR,
> > +                                        (void __user *)tk->addr, addr_lsb);
> > +               /* send no signal to non-current processes */
> >         } else {
> >                 /*
> >                  * Don't use force here, it's convenient if the signal
> > --
> 
> Looks good to me.
> Acked-by: Pankaj Gupta <pankaj.gupta.linux@...il.com>

Thanks!

Acked-by: Naoya Horiguchi <naoya.horiguchi@....com>