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

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Date:   Tue, 26 Jan 2021 07:12:17 -0800
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Stephen Rothwell <sfr@...b.auug.org.au>
Cc:     Christian Borntraeger <borntraeger@...ibm.com>,
        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>,
        Thomas Gleixner <tglx@...utronix.de>,
        Frederic Weisbecker <frederic@...nel.org>
Subject: Re: [PATCH] s390: allow reschedule on syscall restart

On Tue, Jan 26, 2021 at 09:25:53PM +1100, Stephen Rothwell wrote:
> Hi all,
> 
> On Tue, 26 Jan 2021 07:59:51 +0100 Christian Borntraeger <borntraeger@...ibm.com> wrote:
> >
> > On 21.01.21 15:39, Sven Schnelle 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();  
> > 
> > Yesterdays next now fails with
> > 
> > 
> > arch/s390/kernel/syscall.c: In function '__do_syscall':
> > arch/s390/kernel/syscall.c:165:3: error: implicit declaration of function 'sched_resched_local_allow' [-Werror=implicit-function-declaration]
> >   165 |   sched_resched_local_allow();
> >       |   ^~~~~~~~~~~~~~~~~~~~~~~~~
> > cc1: some warnings being treated as errors
> > make[2]: *** [scripts/Makefile.build:288: arch/s390/kernel/syscall.o] Error 1
> > make[2]: *** Waiting for unfinished jobs....
> > make[1]: *** [scripts/Makefile.build:530: arch/s390/kernel] Error 2
> > make[1]: *** Waiting for unfinished jobs....
> 
> I have now removed the merge fix up for tomorrow.  It seems that the
> commits that needed it have been removed :-(

Review comments mean that they need rework, apologies for the hassle!

							Thanx, Paul