Messages in this thread | | | Date | Tue, 24 Jun 2014 14:35:35 -0600 | From | Stephen Warren <> | Subject | Re: [PATCH 2/6] irq_work: Implement remote queueing |
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On 06/24/2014 02:33 PM, Stephen Warren wrote: > On 06/10/2014 09:15 AM, Frederic Weisbecker wrote: >> irq work currently only supports local callbacks. However its code >> is mostly ready to run remote callbacks and we have some potential user. >> >> The full nohz subsystem currently open codes its own remote irq work >> on top of the scheduler ipi when it wants a CPU to reevaluate its next >> tick. However this ad hoc solution bloats the scheduler IPI. >> >> Lets just extend the irq work subsystem to support remote queuing on top >> of the generic SMP IPI to handle this kind of user. This shouldn't add >> noticeable overhead. > > I'm running next-20140624 on an ARM system, and this patch causes CPU > hot(un)plug to Oops for me; the following fires: > > void irq_work_run(void) > { > BUG_ON(!in_irq()); > > I found that Linus's master (8b8f5d971584 "Merge tag 'compress-3.16-rc3' > of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core") > works fine. I found that this commit inside the tip(?) tree works fine > (478850160636 "irq_work: Implement remote queueing"). However, if I > merge the two together, I hit that BUG_ON.
I forgot to mention that the conflicting commit from Linus' tree is 8d056c48e486 "CPU hotplug, smp: flush any pending IPI callbacks before CPU offline".
> I think the issue is: > > This commit adds a call from > generic_smp_call_function_single_interrupt() to irq_work_run(). > > Srivatsa's patch adds a call from hotplug_cfd() to > flush_smp_call_function_queue() to, which I imagine happens in > non-interrupt context. Note that this patch moves most of the body of > generic_smp_call_function_single_interrupt() into > flush_smp_call_function_queue().
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