linux-kernel - Re: [PATCH v0.9.1 3/6] sched/umcg: implement UMCG syscalls

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Date:   Mon, 29 Nov 2021 16:05:52 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Peter Oskolkov <posk@...k.io>, Ingo Molnar <mingo@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-api@...r.kernel.org, Paul Turner <pjt@...gle.com>,
        Ben Segall <bsegall@...gle.com>,
        Peter Oskolkov <posk@...gle.com>,
        Andrei Vagin <avagin@...gle.com>, Jann Horn <jannh@...gle.com>,
        Thierry Delisle <tdelisle@...terloo.ca>
Subject: Re: [PATCH v0.9.1 3/6] sched/umcg: implement UMCG syscalls

On Sat, Nov 27, 2021 at 01:45:20AM +0100, Thomas Gleixner wrote:
> On Fri, Nov 26 2021 at 22:59, Peter Zijlstra wrote:
> > On Fri, Nov 26, 2021 at 10:08:14PM +0100, Thomas Gleixner wrote:
> >> > +		if (timo)
> >> > +			hrtimer_sleeper_start_expires(&timeout, HRTIMER_MODE_ABS);
> >> > +
> >> > +		freezable_schedule();
> >> 
> >> You can replace the whole hrtimer foo with
> >> 
> >>                 if (!schedule_hrtimeout_range_clock(timo ? &timo : NULL,
> >>                                                     tsk->timer_slack_ns,
> >>                                                     HRTIMER_MODE_ABS,
> >>                                                     tsk->umcg_clock)) {
> >>                 	ret = -ETIMEOUT;
> >>                         break;
> >>                 }
> >
> > That seems to loose the freezable crud.. then again, since we're
> > interruptible, that shouldn't matter. Lemme go do that.
> 
> We could add a freezable wrapper for that if necessary.

I should just finish rewriting that freezer crap and then we can delete
it all :-) But I don't think that's needed in this case, as long as
we're interruptible we'll pass through the signal path which has a
try_to_freezer() in it.