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From: Petr Mladek <pmladek@suse.com>
To: Miroslav Benes <mbenes@suse.cz>
Cc: Peter Zijlstra <peterz@infradead.org>,
	gor@linux.ibm.com, jpoimboe@redhat.com, jikos@kernel.org,
	mingo@kernel.org, linux-kernel@vger.kernel.org,
	joe.lawrence@redhat.com, fweisbec@gmail.com, tglx@linutronix.de,
	hca@linux.ibm.com, svens@linux.ibm.com, sumanthk@linux.ibm.com,
	live-patching@vger.kernel.org, paulmck@kernel.org
Subject: Re: [RFC][PATCH 5/7] sched,livepatch: Use wake_up_if_idle()
Date: Thu, 23 Sep 2021 14:19:17 +0200	[thread overview]
Message-ID: <YUxwxUPLs0ig6d5S@alley> (raw)
In-Reply-To: <alpine.LSU.2.21.2109221458230.442@pobox.suse.cz>

On Wed 2021-09-22 15:05:03, Miroslav Benes wrote:
> > @@ -405,8 +405,10 @@ void klp_try_complete_transition(void)
> >  	for_each_possible_cpu(cpu) {
> >  		task = idle_task(cpu);
> >  		if (cpu_online(cpu)) {
> > -			if (!klp_try_switch_task(task))
> > -				complete = false;
> > +			int ret = klp_try_switch_task(task);
> > +			if (ret == -EBUSY)
> > +				wake_up_if_idle(cpu);
> > +			complete = !ret;
> 
> This is broken. You can basically change "complete" only to false (when it 
> applies). This could leave some tasks in the old patching state.

I was a bit confused by Mirek's comment ;-) Anyway, the following works for me:

@@ -406,9 +406,12 @@ void klp_try_complete_transition(void)
 		task = idle_task(cpu);
 		if (cpu_online(cpu)) {
 			int ret = klp_try_switch_task(task);
-			if (ret == -EBUSY)
-				wake_up_if_idle(cpu);
-			complete = !ret;
+			if (ret) {
+				complete = false;
+				/* Make idle task go through the main loop. */
+				if (ret == -EBUSY)
+					wake_up_if_idle(cpu);
+			}
 		} else if (task->patch_state != klp_target_state) {
 			/* offline idle tasks can be switched immediately */
 			clear_tsk_thread_flag(task, TIF_PATCH_PENDING);

Best Regards,
Petr

  reply	other threads:[~2021-09-23 12:19 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-22 11:05 [RFC][PATCH 0/7] sched,rcu,context_tracking,livepatch: Improve livepatch task transitions for idle and NOHZ_FULL cpus Peter Zijlstra
2021-09-22 11:05 ` [RFC][PATCH 1/7] sched,rcu: Rework try_invoke_on_locked_down_task() Peter Zijlstra
2021-09-22 11:05 ` [RFC][PATCH 2/7] sched: Fix task_try_func() Peter Zijlstra
2021-09-22 11:05 ` [RFC][PATCH 3/7] sched,livepatch: Use task_try_func() Peter Zijlstra
2021-09-23 12:05   ` Petr Mladek
2021-09-23 13:17     ` Peter Zijlstra
2021-09-23 13:47       ` Peter Zijlstra
2021-09-22 11:05 ` [RFC][PATCH 4/7] sched: Simplify wake_up_*idle*() Peter Zijlstra
2021-09-22 11:05 ` [RFC][PATCH 5/7] sched,livepatch: Use wake_up_if_idle() Peter Zijlstra
2021-09-22 13:05   ` Miroslav Benes
2021-09-23 12:19     ` Petr Mladek [this message]
2021-09-22 11:05 ` [RFC][PATCH 6/7] context_tracking: Provide SMP ordering using RCU Peter Zijlstra
2021-09-22 15:17   ` Paul E. McKenney
2021-09-22 19:33     ` Peter Zijlstra
2021-09-22 19:47       ` Peter Zijlstra
2021-09-22 19:59         ` Paul E. McKenney
2021-09-22 19:53       ` Paul E. McKenney
2021-09-22 20:02         ` Peter Zijlstra
2021-09-23 12:10   ` Petr Mladek
2021-09-24 18:57   ` Joel Savitz
2021-09-27 14:33     ` Petr Mladek
2021-09-22 11:05 ` [RFC][PATCH 7/7] livepatch,context_tracking: Avoid disturbing NOHZ_FULL tasks Peter Zijlstra
2021-09-23 13:14   ` Petr Mladek
2021-09-23 13:28     ` Peter Zijlstra
2021-09-24  7:33       ` Petr Mladek
2021-09-23 13:22 ` [RFC][PATCH 0/7] sched,rcu,context_tracking,livepatch: Improve livepatch task transitions for idle and NOHZ_FULL cpus Petr Mladek

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