Commit a33d7d94 authored by Steven Rostedt (VMware)'s avatar Steven Rostedt (VMware)
Browse files

tracing: Make sure RCU is watching before calling a stack trace 

As stack tracing now requires "rcu watching", force RCU to be watching when
recording a stack trace.

Link: http://lkml.kernel.org/r/20170512172449.879684501@goodmis.org



Acked-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
parent 545a0281

kernel/trace/trace.c

+30 −1
Original line number Diff line number Diff line
@@ -2568,7 +2568,36 @@ static inline void ftrace_trace_stack(struct trace_array *tr, 
void __trace_stack(struct trace_array *tr, unsigned long flags, int skip,

		   int pc)

{

	__ftrace_trace_stack(tr->trace_buffer.buffer, flags, skip, pc, NULL);

	struct ring_buffer *buffer = tr->trace_buffer.buffer;



	if (rcu_is_watching()) {

		__ftrace_trace_stack(buffer, flags, skip, pc, NULL);

		return;

	}



	/*

	 * When an NMI triggers, RCU is enabled via rcu_nmi_enter(),

	 * but if the above rcu_is_watching() failed, then the NMI

	 * triggered someplace critical, and rcu_irq_enter() should

	 * not be called from NMI.

	 */

	if (unlikely(in_nmi()))

		return;



	/*

	 * It is possible that a function is being traced in a

	 * location that RCU is not watching. A call to

	 * rcu_irq_enter() will make sure that it is, but there's

	 * a few internal rcu functions that could be traced

	 * where that wont work either. In those cases, we just

	 * do nothing.

	 */

	if (unlikely(rcu_irq_enter_disabled()))

		return;



	rcu_irq_enter_irqson();

	__ftrace_trace_stack(buffer, flags, skip, pc, NULL);

	rcu_irq_exit_irqson();

}



/**