path: root/arch
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authorSteven Rostedt <rostedt@goodmis.org>2014-02-04 14:13:15 -0500
committerIngo Molnar <mingo@kernel.org>2014-02-09 13:09:08 +0100
commit569d6557ab957d6ae7e97a46ae669174be4189e6 (patch)
treece06766e54fdc96c68a61a2121e730df3f305a95 /arch
parent494479038d97f1b9f76fc633a360a681acdf035c (diff)
x86: Use preempt_disable_notrace() in cycles_2_ns()
When debug preempt is enabled, preempt_disable() can be traced by function and function graph tracing. There's a place in the function graph tracer that calls trace_clock() which eventually calls cycles_2_ns() outside of the recursion protection. When cycles_2_ns() calls preempt_disable() it gets traced and the graph tracer will go into a recursive loop causing a crash or worse, a triple fault. Simple fix is to use preempt_disable_notrace() in cycles_2_ns, which makes sense because the preempt_disable() tracing may use that code too, and it tracing it, even with recursion protection is rather pointless. Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Acked-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/20140204141315.2a968a72@gandalf.local.home Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch')
1 files changed, 2 insertions, 2 deletions
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 19e5adb49a27..acb3b606613e 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -209,7 +209,7 @@ static inline unsigned long long cycles_2_ns(unsigned long long cyc)
* dance when its actually needed.
- preempt_disable();
+ preempt_disable_notrace();
data = this_cpu_read(cyc2ns.head);
tail = this_cpu_read(cyc2ns.tail);
@@ -229,7 +229,7 @@ static inline unsigned long long cycles_2_ns(unsigned long long cyc)
if (!--data->__count)
this_cpu_write(cyc2ns.tail, data);
- preempt_enable();
+ preempt_enable_notrace();
return ns;