From: "Paul E. McKenney" <paulmck@kernel.org> To: Thomas Gleixner <tglx@linutronix.de> Cc: Zhouyi Zhou <zhouzhouyi@gmail.com>, fweisbec@gmail.com, 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: Sun, 27 Nov 2022 09:53:17 -0800 [thread overview] Message-ID: <20221127175317.GF4001@paulmck-ThinkPad-P17-Gen-1> (raw) In-Reply-To: <87v8n0woxv.ffs@tglx> On Sun, Nov 27, 2022 at 01:40:28PM +0100, Thomas Gleixner wrote: [ . . . ] > >> No. We are not exporting this just to make a bogus test case happy. > >> > >> Fix the torture code to handle -EBUSY correctly. > > I am going to do a study on this, for now, I do a grep in the kernel tree: > > find . -name "*.c"|xargs grep cpuhp_setup_state|wc -l > > The result of the grep command shows that there are 268 > > cpuhp_setup_state* cases. > > which may make our task more complicated. > > Why? The whole point of this torture thing is to stress the > infrastructure. Indeed. > There are quite some reasons why a CPU-hotplug or a hot-unplug operation > can fail, which is not a fatal problem, really. > > So if a CPU hotplug operation fails, then why can't the torture test > just move on and validate that the system still behaves correctly? > > That gives us more coverage than just testing the good case and giving > up when something unexpected happens. Agreed, with access to a function like the tick_nohz_full_timekeeper() suggested earlier in this email thread, then yes, it would make sense to try to offline the CPU anyway, then forgive the failure in cases where the CPU matches that indicated by tick_nohz_full_timekeeper(). > I even argue that the torture test should inject random failures into > the hotplug state machine to achieve extended code coverage. I could imagine torture_onoff() telling various CPU-hotplug notifiers to refuse the transition using some TBD interface. That would better test the CPU-hotplug common code's ability to deal with failures. Or did you have something else/additional in mind? Thanx, Paul
WARNING: multiple messages have this Message-ID (diff)
From: "Paul E. McKenney" <paulmck@kernel.org> To: Thomas Gleixner <tglx@linutronix.de> Cc: dave@stgolabs.net, linuxppc-dev@lists.ozlabs.org, josh@joshtriplett.org, linux-kernel@vger.kernel.org, Zhouyi Zhou <zhouzhouyi@gmail.com>, fweisbec@gmail.com, mingo@kernel.org Subject: Re: [PATCH linux-next][RFC]torture: avoid offline tick_do_timer_cpu Date: Sun, 27 Nov 2022 09:53:17 -0800 [thread overview] Message-ID: <20221127175317.GF4001@paulmck-ThinkPad-P17-Gen-1> (raw) In-Reply-To: <87v8n0woxv.ffs@tglx> On Sun, Nov 27, 2022 at 01:40:28PM +0100, Thomas Gleixner wrote: [ . . . ] > >> No. We are not exporting this just to make a bogus test case happy. > >> > >> Fix the torture code to handle -EBUSY correctly. > > I am going to do a study on this, for now, I do a grep in the kernel tree: > > find . -name "*.c"|xargs grep cpuhp_setup_state|wc -l > > The result of the grep command shows that there are 268 > > cpuhp_setup_state* cases. > > which may make our task more complicated. > > Why? The whole point of this torture thing is to stress the > infrastructure. Indeed. > There are quite some reasons why a CPU-hotplug or a hot-unplug operation > can fail, which is not a fatal problem, really. > > So if a CPU hotplug operation fails, then why can't the torture test > just move on and validate that the system still behaves correctly? > > That gives us more coverage than just testing the good case and giving > up when something unexpected happens. Agreed, with access to a function like the tick_nohz_full_timekeeper() suggested earlier in this email thread, then yes, it would make sense to try to offline the CPU anyway, then forgive the failure in cases where the CPU matches that indicated by tick_nohz_full_timekeeper(). > I even argue that the torture test should inject random failures into > the hotplug state machine to achieve extended code coverage. I could imagine torture_onoff() telling various CPU-hotplug notifiers to refuse the transition using some TBD interface. That would better test the CPU-hotplug common code's ability to deal with failures. Or did you have something else/additional in mind? Thanx, Paul
next prev parent reply other threads:[~2022-11-27 17:53 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 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 [this message] 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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