this commit:
commit d243769d3f83b318813a04a9592bb7cfedc6c280
Author: Hugh Dickins <[email protected]>
Date: Mon Aug 27 16:06:19 2007 +0100
fix bogus hotplug cpu warning
Fix bogus DEBUG_PREEMPT warning on x86_64, when cpu brought online
after bootup: current_is_keventd is right to note its use of
smp_processor_id is preempt-safe, but should use
raw_smp_processor_id to avoid the warning.
- int cpu = smp_processor_id(); /* preempt-safe: keventd is per-cpu */
+ int cpu = raw_smp_processor_id(); /* preempt-safe: keventd is per-cpu */
is incorrect. smp_processor_id() will _not_ warn about true per-cpu
tasks:
/*
* Kernel threads bound to a single CPU can safely use
* smp_processor_id():
*/
this_mask = cpumask_of_cpu(this_cpu);
if (cpus_equal(current->cpus_allowed, this_mask))
goto out;
so if this check triggered for the cpu-offline code it's because keventd
was _not_ per-cpu (perhaps because the cpu offline code broke its
affinity?). So your patch hides a real bug.
Ingo
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