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Mon, 23 Nov 2020 22:39:35 +0000 From: Alex Belits To: "frederic@kernel.org" Subject: Re: [EXT] Re: [PATCH v5 9/9] task_isolation: kick_all_cpus_sync: don't kick isolated cpus Thread-Topic: [EXT] Re: [PATCH v5 9/9] task_isolation: kick_all_cpus_sync: don't kick isolated cpus Thread-Index: AQHWwcJHihlNClCxdEOODDjRi5wCaKnWTJeAgAAC64A= Date: Mon, 23 Nov 2020 22:39:34 +0000 Message-ID: References: <8d887e59ca713726f4fcb25a316e1e932b02823e.camel@marvell.com> <3236b13f42679031960c5605be20664e90e75223.camel@marvell.com> <20201123222907.GC1751@lothringen> In-Reply-To: <20201123222907.GC1751@lothringen> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: kernel.org; dkim=none (message not signed) header.d=none;kernel.org; dmarc=none action=none header.from=marvell.com; x-originating-ip: [173.228.7.197] x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: 0e70b603-e4ee-469c-a3a8-08d89000a712 x-ms-traffictypediagnostic: MWHPR1801MB1967: x-ms-exchange-transport-forked: True x-microsoft-antispam-prvs: x-ms-oob-tlc-oobclassifiers: OLM:8273; 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charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, 2020-11-23 at 23:29 +0100, Frederic Weisbecker wrote: > External Email > > ------------------------------------------------------------------- > --- > On Mon, Nov 23, 2020 at 05:58:42PM +0000, Alex Belits wrote: > > From: Yuri Norov > > > > Make sure that kick_all_cpus_sync() does not call CPUs that are > > running > > isolated tasks. > > > > Signed-off-by: Yuri Norov > > [abelits@marvell.com: use safe task_isolation_cpumask() > > implementation] > > Signed-off-by: Alex Belits > > --- > > kernel/smp.c | 14 +++++++++++++- > > 1 file changed, 13 insertions(+), 1 deletion(-) > > > > diff --git a/kernel/smp.c b/kernel/smp.c > > index 4d17501433be..b2faecf58ed0 100644 > > --- a/kernel/smp.c > > +++ b/kernel/smp.c > > @@ -932,9 +932,21 @@ static void do_nothing(void *unused) > > */ > > void kick_all_cpus_sync(void) > > { > > + struct cpumask mask; > > + > > /* Make sure the change is visible before we kick the cpus */ > > smp_mb(); > > - smp_call_function(do_nothing, NULL, 1); > > + > > + preempt_disable(); > > +#ifdef CONFIG_TASK_ISOLATION > > + cpumask_clear(&mask); > > + task_isolation_cpumask(&mask); > > + cpumask_complement(&mask, &mask); > > +#else > > + cpumask_setall(&mask); > > +#endif > > + smp_call_function_many(&mask, do_nothing, NULL, 1); > > + preempt_enable(); > > Same comment about IPIs here. This is different from timers. The original design was based on the idea that every CPU should be able to enter kernel at any time and run kernel code with no additional preparation. Then the only solution is to always do full broadcast and require all CPUs to process it. What I am trying to introduce is the idea of CPU that is not likely to run kernel code any soon, and can afford to go through an additional synchronization procedure on the next entry into kernel. The synchronization is not skipped, it simply happens later, early in kernel entry code. -- Alex _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel