x86: Use preempt_disable_notrace() in cycles_2_ns()
authorSteven Rostedt <rostedt@goodmis.org>
Tue, 4 Feb 2014 19:13:15 +0000 (14:13 -0500)
committerIngo Molnar <mingo@kernel.org>
Sun, 9 Feb 2014 12:09:08 +0000 (13:09 +0100)
commit569d6557ab957d6ae7e97a46ae669174be4189e6
treece06766e54fdc96c68a61a2121e730df3f305a95
parent494479038d97f1b9f76fc633a360a681acdf035c
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>
arch/x86/kernel/tsc.c