50 lines
1.7 KiB
Diff
50 lines
1.7 KiB
Diff
Subject: sched: Do not clear PF_NO_SETAFFINITY flag in select_fallback_rq()
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From: Steven Rostedt <rostedt@goodmis.org>
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Date: Tue, 1 Jul 2014 11:14:44 -0400
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.0/patches-4.0.5-rt3.tar.xz
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I talked with Peter Zijlstra about this, and he told me that the clearing
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of the PF_NO_SETAFFINITY flag was to deal with the optimization of
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migrate_disable/enable() that ignores tasks that have that flag set. But
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that optimization was removed when I did a rework of the cpu hotplug code.
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I found that ignoring tasks that had that flag set would cause those tasks
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to not sync with the hotplug code and cause the kernel to crash. Thus it
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needed to not treat them special and those tasks had to go though the same
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work as tasks without that flag set.
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Now that those tasks are not treated special, there's no reason to clear the
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flag.
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May still need to be tested as the migrate_me() code does not ignore those
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flags.
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Cc: stable-rt@vger.kernel.org
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Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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Cc: Clark Williams <williams@redhat.com>
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Cc: Peter Zijlstra <peterz@infradead.org>
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Link: http://lkml.kernel.org/r/20140701111444.0cfebaa1@gandalf.local.home
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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---
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---
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kernel/sched/core.c | 6 ------
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1 file changed, 6 deletions(-)
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--- a/kernel/sched/core.c
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+++ b/kernel/sched/core.c
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@@ -1433,12 +1433,6 @@ static int select_fallback_rq(int cpu, s
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}
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}
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- /*
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- * Clear PF_NO_SETAFFINITY, otherwise we wreckage
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- * migrate_disable/enable. See optimization for
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- * PF_NO_SETAFFINITY tasks there.
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- */
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- p->flags &= ~PF_NO_SETAFFINITY;
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return dest_cpu;
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}
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