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[PATCH] sys_sched_getaffinity() & hotplug 

Change sched_getaffinity() so that it returns a bitmap that indicates the
legally schedulable cpus that a task is allowed to run on.

Without this patch, if CONFIG_HOTPLUG_CPU is enabled, sched_getaffinity()
unconditionally returns (at least on IA64) a mask with NR_CPUS bits set.
This conveys no useful infornmation except for a kernel compile option.

This fixes a breakage we obseved running recent kernels. We have MPI jobs
that use sched_getaffinity() to determine where to place their threads.
Placing them on non-existant cpus is problematic :-)

Signed-off-by: Jack Steiner <steiner@sgi.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: Nathan Lynch <ntl@pobox.com>
Cc: Paul Jackson <pj@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Jack Steiner 2006-02-01 03:05:18 -08:00 committed by Linus Torvalds
parent 0f07496144
commit 2f7016d917
1 changed files with 1 additions and 1 deletions
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2
kernel/sched.c
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@ -4031,7 +4031,7 @@ long sched_getaffinity(pid_t pid, cpumask_t *mask)
goto out_unlock;
retval = 0;
cpus_and(*mask, p->cpus_allowed, cpu_possible_map);
cpus_and(*mask, p->cpus_allowed, cpu_online_map);
out_unlock:
read_unlock(&tasklist_lock);