From: "Steven Rostedt (VMware)" <[email protected]> As stack tracing now requires "rcu watching", force RCU to be watching when recording a stack trace.
Link: http://lkml.kernel.org/r/[email protected] Cc: "Paul E. McKenney" <[email protected]> Signed-off-by: Steven Rostedt (VMware) <[email protected]> --- kernel/trace/trace.c | 23 ++++++++++++++++++++++- 1 file changed, 22 insertions(+), 1 deletion(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index fcc9a2d..a1b45b4 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -2568,7 +2568,28 @@ 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; + + /* When an NMI triggers, RCU is enabled via rcu_nmi_enter() */ + if (in_nmi()) { + __ftrace_trace_stack(buffer, flags, skip, pc, NULL); + 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(); + __ftrace_trace_stack(buffer, flags, skip, pc, NULL); + rcu_irq_exit(); } /** -- 2.9.3
