diff options
author | Oleg Nesterov <oleg@redhat.com> | 2014-10-05 16:23:22 -0400 |
---|---|---|
committer | Ingo Molnar <mingo@kernel.org> | 2014-10-28 05:46:05 -0400 |
commit | 009f60e2763568cdcd75bd1cf360c7c7165e2e60 (patch) | |
tree | 190e6cb5857bd0c2788939fe4004a128e655ec49 /kernel/sched | |
parent | 6419265899d9bd27e5ff9f8b43db3715407fc2ba (diff) |
sched: stop the unbound recursion in preempt_schedule_context()
preempt_schedule_context() does preempt_enable_notrace() at the end
and this can call the same function again; exception_exit() is heavy
and it is quite possible that need-resched is true again.
1. Change this code to dec preempt_count() and check need_resched()
by hand.
2. As Linus suggested, we can use the PREEMPT_ACTIVE bit and avoid
the enable/disable dance around __schedule(). But in this case
we need to move into sched/core.c.
3. Cosmetic, but x86 forgets to declare this function. This doesn't
really matter because it is only called by asm helpers, still it
make sense to add the declaration into asm/preempt.h to match
preempt_schedule().
Reported-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Graf <agraf@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Anvin <hpa@zytor.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Chuck Ebbert <cebbert.lkml@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/20141005202322.GB27962@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/sched')
-rw-r--r-- | kernel/sched/core.c | 41 |
1 files changed, 41 insertions, 0 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index dde8adb7d0c0..240157c13ddc 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c | |||
@@ -2951,6 +2951,47 @@ asmlinkage __visible void __sched notrace preempt_schedule(void) | |||
2951 | } | 2951 | } |
2952 | NOKPROBE_SYMBOL(preempt_schedule); | 2952 | NOKPROBE_SYMBOL(preempt_schedule); |
2953 | EXPORT_SYMBOL(preempt_schedule); | 2953 | EXPORT_SYMBOL(preempt_schedule); |
2954 | |||
2955 | #ifdef CONFIG_CONTEXT_TRACKING | ||
2956 | /** | ||
2957 | * preempt_schedule_context - preempt_schedule called by tracing | ||
2958 | * | ||
2959 | * The tracing infrastructure uses preempt_enable_notrace to prevent | ||
2960 | * recursion and tracing preempt enabling caused by the tracing | ||
2961 | * infrastructure itself. But as tracing can happen in areas coming | ||
2962 | * from userspace or just about to enter userspace, a preempt enable | ||
2963 | * can occur before user_exit() is called. This will cause the scheduler | ||
2964 | * to be called when the system is still in usermode. | ||
2965 | * | ||
2966 | * To prevent this, the preempt_enable_notrace will use this function | ||
2967 | * instead of preempt_schedule() to exit user context if needed before | ||
2968 | * calling the scheduler. | ||
2969 | */ | ||
2970 | asmlinkage __visible void __sched notrace preempt_schedule_context(void) | ||
2971 | { | ||
2972 | enum ctx_state prev_ctx; | ||
2973 | |||
2974 | if (likely(!preemptible())) | ||
2975 | return; | ||
2976 | |||
2977 | do { | ||
2978 | __preempt_count_add(PREEMPT_ACTIVE); | ||
2979 | /* | ||
2980 | * Needs preempt disabled in case user_exit() is traced | ||
2981 | * and the tracer calls preempt_enable_notrace() causing | ||
2982 | * an infinite recursion. | ||
2983 | */ | ||
2984 | prev_ctx = exception_enter(); | ||
2985 | __schedule(); | ||
2986 | exception_exit(prev_ctx); | ||
2987 | |||
2988 | __preempt_count_sub(PREEMPT_ACTIVE); | ||
2989 | barrier(); | ||
2990 | } while (need_resched()); | ||
2991 | } | ||
2992 | EXPORT_SYMBOL_GPL(preempt_schedule_context); | ||
2993 | #endif /* CONFIG_CONTEXT_TRACKING */ | ||
2994 | |||
2954 | #endif /* CONFIG_PREEMPT */ | 2995 | #endif /* CONFIG_PREEMPT */ |
2955 | 2996 | ||
2956 | /* | 2997 | /* |