From: Thomas Gleixner <tglx@linutronix.de>
To: Peter Zijlstra <peterz@infradead.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
Frederic Weisbecker <frederic@kernel.org>,
Paul McKenney <paulmck@kernel.org>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Subject: Re: [patch V2 7/9] softirq: Replace barrier() with cpu_relax() in tasklet_unlock_wait()
Date: Mon, 07 Dec 2020 16:21:21 +0100 [thread overview]
Message-ID: <87wnxt63ri.fsf@nanos.tec.linutronix.de> (raw)
In-Reply-To: <20201207113958.GJ3040@hirez.programming.kicks-ass.net>
On Mon, Dec 07 2020 at 12:39, Peter Zijlstra wrote:
> On Fri, Dec 04, 2020 at 06:01:58PM +0100, Thomas Gleixner wrote:
>> static inline void tasklet_unlock_wait(struct tasklet_struct *t)
>> {
>> - while (test_bit(TASKLET_STATE_RUN, &(t)->state)) { barrier(); }
>> + while (test_bit(TASKLET_STATE_RUN, &(t)->state))
>> + cpu_relax();
>> }
>
> Wouldn't it be nicer to stick a completion in tasklet_struct ? Or at the
> very least use wait_var_event() or something?
It would be nicer. Just need to audit all possible callers. That would
lose the implicit boosting of the preempted softirq thread, but these
wait pathes should not be in any way relevant for user task
latencies. Emphasis on should.
Lemme stare at the callers including the ones which have it wrapped into
some other inline just because.
Thanks,
tglx
next prev parent reply other threads:[~2020-12-07 15:22 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-04 17:01 [patch V2 0/9] softirq: Make it RT aware Thomas Gleixner
2020-12-04 17:01 ` [patch V2 1/9] softirq: Add RT specific softirq accounting Thomas Gleixner
2020-12-07 13:06 ` Frederic Weisbecker
2020-12-04 17:01 ` [patch V2 2/9] irqtime: Make accounting correct on RT Thomas Gleixner
2020-12-07 0:23 ` Frederic Weisbecker
2020-12-07 0:57 ` Thomas Gleixner
2020-12-07 1:14 ` Frederic Weisbecker
2020-12-07 13:27 ` Frederic Weisbecker
2020-12-07 14:44 ` Thomas Gleixner
2020-12-04 17:01 ` [patch V2 3/9] softirq: Move various protections into inline helpers Thomas Gleixner
2020-12-07 13:37 ` Frederic Weisbecker
2020-12-04 17:01 ` [patch V2 4/9] softirq: Make softirq control and processing RT aware Thomas Gleixner
2020-12-07 14:16 ` Frederic Weisbecker
2020-12-07 15:08 ` Thomas Gleixner
2020-12-08 0:08 ` Frederic Weisbecker
2020-12-09 10:11 ` Peter Zijlstra
2020-12-09 12:36 ` Thomas Gleixner
2020-12-09 12:42 ` Peter Zijlstra
2020-12-09 13:30 ` Thomas Gleixner
2020-12-09 10:34 ` Peter Zijlstra
2020-12-04 17:01 ` [patch V2 5/9] tick/sched: Prevent false positive softirq pending warnings on RT Thomas Gleixner
2020-12-08 12:23 ` Frederic Weisbecker
2020-12-04 17:01 ` [patch V2 6/9] rcu: Prevent false positive softirq warning " Thomas Gleixner
2020-12-04 17:59 ` Paul E. McKenney
2020-12-04 17:01 ` [patch V2 7/9] softirq: Replace barrier() with cpu_relax() in tasklet_unlock_wait() Thomas Gleixner
2020-12-07 11:39 ` Peter Zijlstra
2020-12-07 15:21 ` Thomas Gleixner [this message]
2020-12-04 17:01 ` [patch V2 8/9] tasklets: Use static inlines for stub implementations Thomas Gleixner
2020-12-04 17:02 ` [patch V2 9/9] tasklets: Prevent kill/unlock_wait deadlock on RT Thomas Gleixner
2020-12-07 11:47 ` Peter Zijlstra
2020-12-07 14:00 ` Sebastian Andrzej Siewior
2020-12-07 14:27 ` Peter Zijlstra
2020-12-07 17:55 ` Thomas Gleixner
2020-12-07 15:22 ` Thomas Gleixner
2020-12-07 15:39 ` Sebastian Andrzej Siewior
2020-12-07 17:49 ` Thomas Gleixner
2020-12-07 17:50 ` Thomas Gleixner
2020-12-06 10:05 ` [patch V2 0/9] softirq: Make it RT aware Sebastian Andrzej Siewior
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