lkml.org 
[lkml]   [2008]   [Oct]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: [PATCH 1/7] work_on_cpu: helper for doing task on a CPU.
Date
On Friday 24 October 2008 01:36:05 Gautham R Shenoy wrote:
> OK, how about doing the following? That will solve the problem
> of deadlock you pointed out in patch 6.
>
> get_online_cpus();
> if (likely(per_cpu(cpu_state, cpuid) == CPU_ONLINE)) {
> schedule_work_on(cpu, &wfc.work);
> flush_work(&wfc.work);
> } else if (per_cpu(cpu_state, cpuid) != CPU_DEAD)) {
> /*
> * We're the CPU-Hotplug thread. Call the
> * function synchronously so that we don't
> * deadlock with any pending work-item blocked
> * on get_online_cpus()
> */
> cpumask_t orignal_mask = current->cpus_allowed;
> set_cpus_allowed_ptr(current, &cpumask_of_cpu(cpu);
> wfc.ret = fn(arg);
> set_cpus_allowed_ptr(current, &original_mask);
> }

Hi Gautham, Oleg,

Unfortunately that's exactly what I'm trying to get away from: another cpumask
on the stack :(

The cpu hotplug thread is just whoever wrote 0 to "online" in sys. And in
fact it already plays with its cpumask, which should be fixed too.

I think we should BUG_ON(per_cpu(cpu_state, cpuid) != CPU_DEAD) to ensure we
never use work_on_cpu in the hotplug cpu path. Then we use
smp_call_function() for that hard intel_cacheinfo case. Finally, we fix the
cpu hotplug path to use schedule_work_on() itself rather than playing games
with cpumask.

If you agree, I'll spin the patches...

Thanks for the brainpower,
Rusty.


\
 
 \ /
  Last update: 2008-10-24 05:07    [W:0.193 / U:0.672 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site