From: Frederic Weisbecker <frederic@kernel.org> To: "Paul E. McKenney" <paulmck@kernel.org> Cc: Zhouyi Zhou <zhouzhouyi@gmail.com>, fweisbec@gmail.com, tglx@linutronix.de, mingo@kernel.org, dave@stgolabs.net, josh@joshtriplett.org, mpe@ellerman.id.au, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH linux-next][RFC]torture: avoid offline tick_do_timer_cpu Date: Wed, 23 Nov 2022 23:25:43 +0100 [thread overview] Message-ID: <20221123222543.GB1395324@lothringen> (raw) In-Reply-To: <20221122013754.GY4001@paulmck-ThinkPad-P17-Gen-1> On Mon, Nov 21, 2022 at 05:37:54PM -0800, Paul E. McKenney wrote: > On Mon, Nov 21, 2022 at 11:51:40AM +0800, Zhouyi Zhou wrote: > > @@ -358,7 +359,16 @@ torture_onoff(void *arg) > > schedule_timeout_interruptible(HZ / 10); > > continue; > > } > > +#ifdef CONFIG_NO_HZ_FULL > > + /* do not offline tick do timer cpu */ > > + if (tick_nohz_full_running) { > > + cpu = (torture_random(&rand) >> 4) % maxcpu; > > + if (cpu >= tick_do_timer_cpu) > > Why is this ">=" instead of "=="? > > > + cpu = (cpu + 1) % (maxcpu + 1); > > + } else > > +#else > > cpu = (torture_random(&rand) >> 4) % (maxcpu + 1); > > +#endif > > What happens if the value of tick_do_timer_cpu changes between the time of > the check above and the call to torture_offline() below? Alternatively, > how is such a change in value prevented? It can't, currently tick_do_timer_cpu is fixed when nohz_full is running. It can however have special values at early boot such as TICK_DO_TIMER_NONE. But if rcutorture is initialized after smp, it should be ok. Thanks. > > Thanx, Paul > > > if (!torture_offline(cpu, > > &n_offline_attempts, &n_offline_successes, > > &sum_offline, &min_offline, &max_offline)) > > -- > > 2.34.1 > >
WARNING: multiple messages have this Message-ID (diff)
From: Frederic Weisbecker <frederic@kernel.org> To: "Paul E. McKenney" <paulmck@kernel.org> Cc: dave@stgolabs.net, Zhouyi Zhou <zhouzhouyi@gmail.com>, josh@joshtriplett.org, linux-kernel@vger.kernel.org, fweisbec@gmail.com, tglx@linutronix.de, linuxppc-dev@lists.ozlabs.org, mingo@kernel.org Subject: Re: [PATCH linux-next][RFC]torture: avoid offline tick_do_timer_cpu Date: Wed, 23 Nov 2022 23:25:43 +0100 [thread overview] Message-ID: <20221123222543.GB1395324@lothringen> (raw) In-Reply-To: <20221122013754.GY4001@paulmck-ThinkPad-P17-Gen-1> On Mon, Nov 21, 2022 at 05:37:54PM -0800, Paul E. McKenney wrote: > On Mon, Nov 21, 2022 at 11:51:40AM +0800, Zhouyi Zhou wrote: > > @@ -358,7 +359,16 @@ torture_onoff(void *arg) > > schedule_timeout_interruptible(HZ / 10); > > continue; > > } > > +#ifdef CONFIG_NO_HZ_FULL > > + /* do not offline tick do timer cpu */ > > + if (tick_nohz_full_running) { > > + cpu = (torture_random(&rand) >> 4) % maxcpu; > > + if (cpu >= tick_do_timer_cpu) > > Why is this ">=" instead of "=="? > > > + cpu = (cpu + 1) % (maxcpu + 1); > > + } else > > +#else > > cpu = (torture_random(&rand) >> 4) % (maxcpu + 1); > > +#endif > > What happens if the value of tick_do_timer_cpu changes between the time of > the check above and the call to torture_offline() below? Alternatively, > how is such a change in value prevented? It can't, currently tick_do_timer_cpu is fixed when nohz_full is running. It can however have special values at early boot such as TICK_DO_TIMER_NONE. But if rcutorture is initialized after smp, it should be ok. Thanks. > > Thanx, Paul > > > if (!torture_offline(cpu, > > &n_offline_attempts, &n_offline_successes, > > &sum_offline, &min_offline, &max_offline)) > > -- > > 2.34.1 > >
next prev parent reply other threads:[~2022-11-23 22:25 UTC|newest] Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-11-21 3:51 [PATCH linux-next][RFC]torture: avoid offline tick_do_timer_cpu Zhouyi Zhou 2022-11-22 1:37 ` Paul E. McKenney 2022-11-22 1:37 ` Paul E. McKenney 2022-11-23 2:23 ` Zhouyi Zhou 2022-11-23 2:23 ` Zhouyi Zhou 2022-11-23 18:49 ` Paul E. McKenney 2022-11-23 18:49 ` Paul E. McKenney 2022-11-24 2:35 ` Zhouyi Zhou 2022-11-24 2:35 ` Zhouyi Zhou 2022-11-23 22:25 ` Frederic Weisbecker [this message] 2022-11-23 22:25 ` Frederic Weisbecker 2022-11-23 23:00 ` Paul E. McKenney 2022-11-23 23:00 ` Paul E. McKenney 2022-11-23 22:36 ` Frederic Weisbecker 2022-11-23 22:36 ` Frederic Weisbecker 2022-11-24 2:18 ` Zhouyi Zhou 2022-11-24 2:18 ` Zhouyi Zhou 2022-11-26 17:05 ` Thomas Gleixner 2022-11-27 2:45 ` Zhouyi Zhou 2022-11-27 2:45 ` Zhouyi Zhou 2022-11-27 12:40 ` Thomas Gleixner 2022-11-27 12:40 ` Thomas Gleixner 2022-11-27 17:53 ` Paul E. McKenney 2022-11-27 17:53 ` Paul E. McKenney 2022-11-28 3:00 ` Zhouyi Zhou 2022-11-28 3:00 ` Zhouyi Zhou 2022-11-28 8:12 ` Thomas Gleixner 2022-11-28 8:12 ` Thomas Gleixner 2022-11-28 15:16 ` Paul E. McKenney 2022-11-28 15:16 ` Paul E. McKenney 2023-07-06 7:09 ` Christophe Leroy 2023-07-06 8:13 ` Zhouyi Zhou 2023-07-06 8:13 ` Zhouyi Zhou
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