Messages in this thread Patch in this message | | | Date | Sun, 29 Jan 2006 07:51:04 -0600 | From | Jack Steiner <> | Subject | [PATCH] - sys_sched_getaffinity & hotplug |
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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.
Signed-off-by: Jack Steiner <steiner@sgi.com> Acked-by: Ingo Molnar <mingo@elte.hu>
--- 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 :-)
Index: linux/kernel/sched.c =================================================================== --- linux.orig/kernel/sched.c 2006-01-28 10:13:01.834293691 -0600 +++ linux/kernel/sched.c 2006-01-29 07:15:11.217227453 -0600 @@ -4031,7 +4031,7 @@ long sched_getaffinity(pid_t pid, cpumas 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); - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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