linux-kernel - Re: [PATCH] s390: allow reschedule on syscall restart

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Message-ID: <20210121214358.GX2743@paulmck-ThinkPad-P72>
Date:   Thu, 21 Jan 2021 13:43:58 -0800
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Stephen Rothwell <sfr@...b.auug.org.au>
Cc:     Sven Schnelle <svens@...ux.ibm.com>,
        Linux Next Mailing List <linux-next@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Frederic Weisbecker <frederic@...nel.org>
Subject: Re: [PATCH] s390: allow reschedule on syscall restart

On Fri, Jan 22, 2021 at 08:32:49AM +1100, Stephen Rothwell wrote:
> Hi all,
> 
> On Thu, 21 Jan 2021 15:39:26 +0100 Sven Schnelle <svens@...ux.ibm.com> wrote:
> >
> > Commit 845f44e8ef28 ("sched: Report local wake up on resched blind zone
> > within idle loop") from next-20210121 causes a warning because s390
> > doesn't call sched_resched_local_allow() when restarting a syscall.
> > 
> > Signed-off-by: Sven Schnelle <svens@...ux.ibm.com>
> > ---
> >  arch/s390/kernel/syscall.c | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/arch/s390/kernel/syscall.c b/arch/s390/kernel/syscall.c
> > index bc8e650e377d..2b39ac40f970 100644
> > --- a/arch/s390/kernel/syscall.c
> > +++ b/arch/s390/kernel/syscall.c
> > @@ -162,6 +162,7 @@ void noinstr __do_syscall(struct pt_regs *regs, int per_trap)
> >  		do_syscall(regs);
> >  		if (!test_pt_regs_flag(regs, PIF_SYSCALL_RESTART))
> >  			break;
> > +		sched_resched_local_allow();
> >  		local_irq_enable();
> >  	}
> >  	exit_to_user_mode();
> 
> I add that today as a merge fixup patch to the merge of the rcu tree
> (which contains commit 845f44e8ef28 ("sched: Report local wake up on
> resched blind zone within idle loop") ).

If Frederic has no objections, I will fold this in with attribution.

Either way, good catch!

							Thanx, Paul