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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: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (VMware) 2017-05-12 13:15:45 -04:00
parent 545a028190
commit a33d7d94ee
1 changed files with 30 additions and 1 deletions
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31
kernel/trace/trace.c
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@ -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();
}
/**