Commit 2f7016d9 authored by Jack Steiner's avatar Jack Steiner Committed by Linus Torvalds

[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: default avatarJack Steiner <>
Acked-by: default avatarIngo Molnar <>
Cc: Nathan Lynch <>
Cc: Paul Jackson <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 0f074961
......@@ -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);
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