Messages in this thread Patch in this message | | | Date | Sun, 28 Apr 2019 23:39:03 -0700 | From | tip-bot for Peter Zijlstra <> | Subject | [tip:sched/core] trace: Fix preempt_enable_no_resched() abuse |
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Commit-ID: e8bd5814989b994cf1b0cb179e1c777e40c0f02c Gitweb: https://git.kernel.org/tip/e8bd5814989b994cf1b0cb179e1c777e40c0f02c Author: Peter Zijlstra <peterz@infradead.org> AuthorDate: Tue, 23 Apr 2019 22:03:18 +0200 Committer: Ingo Molnar <mingo@kernel.org> CommitDate: Mon, 29 Apr 2019 08:27:09 +0200
trace: Fix preempt_enable_no_resched() abuse
Unless there is a call into schedule() in the immediate (deterministic) future, one must not use preempt_enable_no_resched(). It can cause a preemption to go missing and thereby cause arbitrary delays, breaking the PREEMPT=y invariant.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Alexei Starovoitov <ast@kernel.org> Cc: Daniel Borkmann <daniel@iogearbox.net> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Roman Gushchin <guro@fb.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Tim Chen <tim.c.chen@linux.intel.com> Cc: Waiman Long <longman@redhat.com> Cc: Will Deacon <will.deacon@arm.com> Cc: huang ying <huang.ying.caritas@gmail.com> Fixes: 2c2d7329d8af ("tracing/ftrace: use preempt_enable_no_resched_notrace in ring_buffer_time_stamp()") Link: https://lkml.kernel.org/r/20190423200318.GY14281@hirez.programming.kicks-ass.net Signed-off-by: Ingo Molnar <mingo@kernel.org> --- kernel/trace/ring_buffer.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 41b6f96e5366..4ee8d8aa3d0f 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -762,7 +762,7 @@ u64 ring_buffer_time_stamp(struct ring_buffer *buffer, int cpu) preempt_disable_notrace(); time = rb_time_stamp(buffer); - preempt_enable_no_resched_notrace(); + preempt_enable_notrace(); return time; }
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