From: Peter Zijlstra <peterz@infradead.org>
To: Nadav Amit <namit@vmware.com>
Cc: Dave Hansen <dave.hansen@intel.com>,
Andy Lutomirski <luto@kernel.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
the arch/x86 maintainers <x86@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Rik van Riel <riel@surriel.com>,
Josh Poimboeuf <jpoimboe@redhat.com>
Subject: Re: [PATCH v3 1/9] smp: Run functions concurrently in smp_call_function_many()
Date: Mon, 22 Jul 2019 21:34:14 +0200 [thread overview]
Message-ID: <20190722193414.GG6698@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <CF32049E-D6AA-4AD5-A276-0CEC84B6DB11@vmware.com>
On Mon, Jul 22, 2019 at 06:41:44PM +0000, Nadav Amit wrote:
> > On Jul 22, 2019, at 11:16 AM, Peter Zijlstra <peterz@infradead.org> wrote:
> >
> > On Fri, Jul 19, 2019 at 11:23:06AM -0700, Dave Hansen wrote:
> >> On 7/18/19 5:58 PM, Nadav Amit wrote:
> >>> @@ -624,16 +622,11 @@ EXPORT_SYMBOL(on_each_cpu);
> >>> void on_each_cpu_mask(const struct cpumask *mask, smp_call_func_t func,
> >>> void *info, bool wait)
> >>> {
> >>> - int cpu = get_cpu();
> >>> + preempt_disable();
> >>>
> >>> - smp_call_function_many(mask, func, info, wait);
> >>> - if (cpumask_test_cpu(cpu, mask)) {
> >>> - unsigned long flags;
> >>> - local_irq_save(flags);
> >>> - func(info);
> >>> - local_irq_restore(flags);
> >>> - }
> >>> - put_cpu();
> >>> + __smp_call_function_many(mask, func, func, info, wait);
> >>> +
> >>> + preempt_enable();
> >>> }
> >>
> >> The get_cpu() was missing it too, but it would be nice to add some
> >> comments about why preempt needs to be off. I was also thinking it
> >> might make sense to do:
> >>
> >> cfd = get_cpu_var(cfd_data);
> >> __smp_call_function_many(cfd, ...);
> >> put_cpu_var(cfd_data);
> >>
> >> instead of the explicit preempt_enable/disable(), but I don't feel too
> >> strongly about it.
> >
> > It is also required for cpu hotplug.
>
> But then smpcfd_dead_cpu() will not respect the “cpu” argument. Do you still
> prefer it this way (instead of the current preempt_enable() /
> preempt_disable())?
I just meant that the preempt_disable() (either form) is required for
hotplug (we must not send IPIs to offline CPUs, that gets things upset).
Personally I don't mind the bare preempt_disable() as you have; but I
think Dave's idea of a comment has merrit.
next prev parent reply other threads:[~2019-07-22 19:34 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-19 0:58 [PATCH v3 0/9] x86: Concurrent TLB flushes Nadav Amit
2019-07-19 0:58 ` [PATCH v3 1/9] smp: Run functions concurrently in smp_call_function_many() Nadav Amit
2019-07-19 18:23 ` Dave Hansen
2019-07-22 18:16 ` Peter Zijlstra
2019-07-22 18:41 ` Nadav Amit
2019-07-22 19:34 ` Peter Zijlstra [this message]
2019-07-22 18:21 ` Peter Zijlstra
2019-07-22 18:34 ` Nadav Amit
2019-07-22 19:19 ` Peter Zijlstra
2019-07-22 18:37 ` Thomas Gleixner
2019-07-22 18:40 ` Nadav Amit
2019-07-22 18:51 ` Thomas Gleixner
2019-07-22 19:02 ` Nadav Amit
2019-07-25 12:36 ` Thomas Gleixner
2019-07-25 19:10 ` Nadav Amit
2019-07-19 0:58 ` [PATCH v3 2/9] x86/mm/tlb: Remove reason as argument for flush_tlb_func_local() Nadav Amit
2019-07-19 0:58 ` [PATCH v3 3/9] x86/mm/tlb: Open-code on_each_cpu_cond_mask() for tlb_is_not_lazy() Nadav Amit
2019-07-19 18:36 ` Dave Hansen
2019-07-19 18:41 ` Nadav Amit
2019-07-19 22:44 ` Joe Perches
2019-07-19 23:02 ` Nadav Amit
2019-07-22 18:27 ` Peter Zijlstra
2019-07-22 19:47 ` Rasmus Villemoes
2019-07-22 19:51 ` Nadav Amit
2019-07-19 0:58 ` [PATCH v3 4/9] x86/mm/tlb: Flush remote and local TLBs concurrently Nadav Amit
2019-07-22 19:14 ` Peter Zijlstra
2019-07-22 19:27 ` Nadav Amit
2019-07-22 19:32 ` Peter Zijlstra
2019-07-26 7:28 ` Juergen Gross
2019-07-31 0:13 ` Michael Kelley
2019-07-19 0:58 ` [PATCH v3 5/9] x86/mm/tlb: Privatize cpu_tlbstate Nadav Amit
2019-07-19 18:38 ` Dave Hansen
2019-07-19 18:43 ` Nadav Amit
2019-07-19 18:48 ` Dave Hansen
2019-07-19 18:54 ` Nadav Amit
2019-07-20 13:58 ` Andy Lutomirski
2019-07-21 20:21 ` Nadav Amit
2019-07-19 0:58 ` [PATCH v3 6/9] x86/mm/tlb: Do not make is_lazy dirty for no reason Nadav Amit
2019-07-19 0:58 ` [PATCH v3 7/9] cpumask: Mark functions as pure Nadav Amit
2019-07-19 0:58 ` [PATCH v3 8/9] x86/mm/tlb: Remove UV special case Nadav Amit
2019-07-19 2:25 ` Mike Travis
2019-07-19 4:58 ` Nadav Amit
2019-07-31 3:11 ` Nadav Amit
2019-07-19 0:58 ` [PATCH v3 9/9] x86/mm/tlb: Remove unnecessary uses of the inline keyword Nadav Amit
2019-07-19 21:36 ` [PATCH v3 0/9] x86: Concurrent TLB flushes Dave Hansen
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