| Subject: sched: Teach migrate_disable about atomic contexts |
| From: Peter Zijlstra <peterz@infradead.org> |
| Date: Fri, 02 Sep 2011 14:41:37 +0200 |
| |
| Subject: sched: teach migrate_disable about atomic contexts |
| From: Peter Zijlstra <a.p.zijlstra@chello.nl> |
| Date: Fri Sep 02 14:29:27 CEST 2011 |
| |
| <NMI> [<ffffffff812dafd8>] spin_bug+0x94/0xa8 |
| [<ffffffff812db07f>] do_raw_spin_lock+0x43/0xea |
| [<ffffffff814fa9be>] _raw_spin_lock_irqsave+0x6b/0x85 |
| [<ffffffff8106ff9e>] ? migrate_disable+0x75/0x12d |
| [<ffffffff81078aaf>] ? pin_current_cpu+0x36/0xb0 |
| [<ffffffff8106ff9e>] migrate_disable+0x75/0x12d |
| [<ffffffff81115b9d>] pagefault_disable+0xe/0x1f |
| [<ffffffff81047027>] copy_from_user_nmi+0x74/0xe6 |
| [<ffffffff810489d7>] perf_callchain_user+0xf3/0x135 |
| |
| Now clearly we can't go around taking locks from NMI context, cure |
| this by short-circuiting migrate_disable() when we're in an atomic |
| context already. |
| |
| Add some extra debugging to avoid things like: |
| |
| preempt_disable() |
| migrate_disable(); |
| |
| preempt_enable(); |
| migrate_enable(); |
| |
| Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> |
| Link: http://lkml.kernel.org/r/1314967297.1301.14.camel@twins |
| Signed-off-by: Thomas Gleixner <tglx@linutronix.de> |
| Link: http://lkml.kernel.org/n/tip-wbot4vsmwhi8vmbf83hsclk6@git.kernel.org |
| --- |
| include/linux/sched.h | 3 +++ |
| kernel/sched/core.c | 21 +++++++++++++++++++++ |
| 2 files changed, 24 insertions(+) |
| |
| Index: linux-stable/include/linux/sched.h |
| =================================================================== |
| --- linux-stable.orig/include/linux/sched.h |
| +++ linux-stable/include/linux/sched.h |
| @@ -1277,6 +1277,9 @@ struct task_struct { |
| unsigned int policy; |
| #ifdef CONFIG_PREEMPT_RT_FULL |
| int migrate_disable; |
| +# ifdef CONFIG_SCHED_DEBUG |
| + int migrate_disable_atomic; |
| +# endif |
| #endif |
| int nr_cpus_allowed; |
| cpumask_t cpus_allowed; |
| Index: linux-stable/kernel/sched/core.c |
| =================================================================== |
| --- linux-stable.orig/kernel/sched/core.c |
| +++ linux-stable/kernel/sched/core.c |
| @@ -5286,6 +5286,17 @@ void migrate_disable(void) |
| unsigned long flags; |
| struct rq *rq; |
| |
| + if (in_atomic()) { |
| +#ifdef CONFIG_SCHED_DEBUG |
| + p->migrate_disable_atomic++; |
| +#endif |
| + return; |
| + } |
| + |
| +#ifdef CONFIG_SCHED_DEBUG |
| + WARN_ON_ONCE(p->migrate_disable_atomic); |
| +#endif |
| + |
| preempt_disable(); |
| if (p->migrate_disable) { |
| p->migrate_disable++; |
| @@ -5334,6 +5345,16 @@ void migrate_enable(void) |
| unsigned long flags; |
| struct rq *rq; |
| |
| + if (in_atomic()) { |
| +#ifdef CONFIG_SCHED_DEBUG |
| + p->migrate_disable_atomic--; |
| +#endif |
| + return; |
| + } |
| + |
| +#ifdef CONFIG_SCHED_DEBUG |
| + WARN_ON_ONCE(p->migrate_disable_atomic); |
| +#endif |
| WARN_ON_ONCE(p->migrate_disable <= 0); |
| |
| preempt_disable(); |