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]> --- Changes since v1: My testing discovered that the stack trace can be called with interrupts enabled, which is a no no to have when calling rcu_irq_enter(). When interrupts are enabled, as with being in an NMI, RCU will also be watching. kernel/trace/trace.c | 26 +++++++++++++++++++++++++- 1 file changed, 25 insertions(+), 1 deletion(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index fcc9a2d..34a98ba 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -2568,7 +2568,31 @@ 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() + * Also, RCU is always enabled when interrupts are. + */ + if (!irqs_disabled() || 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
