90 lines
2.5 KiB
Diff
90 lines
2.5 KiB
Diff
Subject: sched: Teach migrate_disable about atomic contexts
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From: Peter Zijlstra <peterz@infradead.org>
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Date: Fri, 02 Sep 2011 14:41:37 +0200
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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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Subject: sched: teach migrate_disable about atomic contexts
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From: Peter Zijlstra <a.p.zijlstra@chello.nl>
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Date: Fri Sep 02 14:29:27 CEST 2011
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<NMI> [<ffffffff812dafd8>] spin_bug+0x94/0xa8
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[<ffffffff812db07f>] do_raw_spin_lock+0x43/0xea
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[<ffffffff814fa9be>] _raw_spin_lock_irqsave+0x6b/0x85
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[<ffffffff8106ff9e>] ? migrate_disable+0x75/0x12d
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[<ffffffff81078aaf>] ? pin_current_cpu+0x36/0xb0
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[<ffffffff8106ff9e>] migrate_disable+0x75/0x12d
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[<ffffffff81115b9d>] pagefault_disable+0xe/0x1f
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[<ffffffff81047027>] copy_from_user_nmi+0x74/0xe6
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[<ffffffff810489d7>] perf_callchain_user+0xf3/0x135
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Now clearly we can't go around taking locks from NMI context, cure
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this by short-circuiting migrate_disable() when we're in an atomic
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context already.
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Add some extra debugging to avoid things like:
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preempt_disable()
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migrate_disable();
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preempt_enable();
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migrate_enable();
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Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
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Link: http://lkml.kernel.org/r/1314967297.1301.14.camel@twins
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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Link: http://lkml.kernel.org/n/tip-wbot4vsmwhi8vmbf83hsclk6@git.kernel.org
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---
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include/linux/sched.h | 3 +++
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kernel/sched/core.c | 21 +++++++++++++++++++++
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2 files changed, 24 insertions(+)
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--- a/include/linux/sched.h
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+++ b/include/linux/sched.h
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@@ -1321,6 +1321,9 @@ struct task_struct {
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unsigned int policy;
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#ifdef CONFIG_PREEMPT_RT_FULL
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int migrate_disable;
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+# ifdef CONFIG_SCHED_DEBUG
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+ int migrate_disable_atomic;
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+# endif
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#endif
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int nr_cpus_allowed;
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cpumask_t cpus_allowed;
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--- a/kernel/sched/core.c
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+++ b/kernel/sched/core.c
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@@ -4893,6 +4893,17 @@ void migrate_disable(void)
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unsigned long flags;
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struct rq *rq;
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+ if (in_atomic()) {
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+#ifdef CONFIG_SCHED_DEBUG
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+ p->migrate_disable_atomic++;
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+#endif
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+ return;
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+ }
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+
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+#ifdef CONFIG_SCHED_DEBUG
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+ WARN_ON_ONCE(p->migrate_disable_atomic);
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+#endif
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+
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preempt_disable();
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if (p->migrate_disable) {
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p->migrate_disable++;
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@@ -4941,6 +4952,16 @@ void migrate_enable(void)
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unsigned long flags;
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struct rq *rq;
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+ if (in_atomic()) {
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+#ifdef CONFIG_SCHED_DEBUG
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+ p->migrate_disable_atomic--;
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+#endif
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+ return;
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+ }
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+
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+#ifdef CONFIG_SCHED_DEBUG
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+ WARN_ON_ONCE(p->migrate_disable_atomic);
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+#endif
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WARN_ON_ONCE(p->migrate_disable <= 0);
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preempt_disable();
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