Messages in this thread Patch in this message | | | Date | Fri, 19 May 2017 21:27:00 -0400 | From | Steven Rostedt <> | Subject | [for-next][PATCH] tracing: Make sure RCU is watching before calling a stack trace |
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I'll probably just push this to Linus tomorrow along with my other changes.
-- Steve
git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git for-next
Head SHA1: a33d7d94eed92b23fbbc7b0de06a41b2bbaa49e3
Steven Rostedt (VMware) (1): tracing: Make sure RCU is watching before calling a stack trace
---- kernel/trace/trace.c | 31 ++++++++++++++++++++++++++++++- 1 file changed, 30 insertions(+), 1 deletion(-) --------------------------- commit a33d7d94eed92b23fbbc7b0de06a41b2bbaa49e3 Author: Steven Rostedt (VMware) <rostedt@goodmis.org> Date: Fri May 12 13:15:45 2017 -0400
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>
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index fcc9a2d774c3..1122f151466f 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -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(); } /**
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