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Open Source and information security mailing list archives
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Date: Tue, 8 Oct 2013 12:21:42 +0200 From: Peter Zijlstra <peterz@...radead.org> To: Ingo Molnar <mingo@...nel.org> Cc: Christoph Lameter <cl@...ux.com>, Tejun Heo <tj@...nel.org>, akpm@...uxfoundation.org, Eric Dumazet <edumazet@...gle.com>, netdev@...r.kernel.org, Steven Rostedt <srostedt@...hat.com>, linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de> Subject: Re: [raw v1 2/4] [NET] Use raw_cpu ops for SNMP stats On Tue, Oct 08, 2013 at 09:21:14AM +0200, Ingo Molnar wrote: > > * Christoph Lameter <cl@...ux.com> wrote: > > > SNMP stats are not protected by preemption but by bh handling. > > Most forms of bh exclusion work via the preemption count though, and > softirq contexts themselves are generally not preemptible [to other CPUs] > either. > > So the warnings should, in most cases, not trigger. Right, so softirqs run either in the irq tail at which point preempt_count += SOFTIRQ_OFFSET and thus preemption is disabled, or it runs in ksoftirqd which has strict cpu affinity which also disables the warning, and it also increments preempt_count with SOFTIRQ_OFFSET to exclude the softirq from interrupts while its running, also disabling the warning. So it should very much not trigger.. if it does you want to know about it. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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