From: "Steven Rostedt (VMware)" <[email protected]> Stack tracing discovered that there's a small location inside the RCU infrastructure where calling rcu_irq_enter() does not work. As trace events use rcu_irq_enter() it must make sure that it is functionable. A check against rcu_irq_enter_disabled() is added with a WARN_ON_ONCE() as no trace event should ever be used in that part of RCU. If the warning is triggered, then the trace event is ignored.
Link: http://lkml.kernel.org/r/[email protected] Cc: Mathieu (making code boring) Desnoyers <[email protected]> Signed-off-by: Steven Rostedt (VMware) <[email protected]> --- Mathieu, There! Are you now satisfied? include/linux/tracepoint.h | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h index f72fcfe..7f98d50 100644 --- a/include/linux/tracepoint.h +++ b/include/linux/tracepoint.h @@ -128,7 +128,7 @@ extern void syscall_unregfunc(void); * as "(void *, void)". The DECLARE_TRACE_NOARGS() will pass in just * "void *data", where as the DECLARE_TRACE() will pass in "void *data, proto". */ -#define __DO_TRACE(tp, proto, args, cond, prercu, postrcu) \ +#define __DO_TRACE(tp, proto, args, cond, rcucheck, prercu, postrcu) \ do { \ struct tracepoint_func *it_func_ptr; \ void *it_func; \ @@ -136,6 +136,8 @@ extern void syscall_unregfunc(void); \ if (!(cond)) \ return; \ + if (rcucheck) \ + return; \ prercu; \ rcu_read_lock_sched_notrace(); \ it_func_ptr = rcu_dereference_sched((tp)->funcs); \ @@ -151,7 +153,7 @@ extern void syscall_unregfunc(void); } while (0) #ifndef MODULE -#define __DECLARE_TRACE_RCU(name, proto, args, cond, data_proto, data_args) \ +#define __DECLARE_TRACE_RCU(name, proto, args, cond, data_proto, data_args) \ static inline void trace_##name##_rcuidle(proto) \ { \ if (static_key_false(&__tracepoint_##name.key)) \ @@ -159,6 +161,7 @@ extern void syscall_unregfunc(void); TP_PROTO(data_proto), \ TP_ARGS(data_args), \ TP_CONDITION(cond), \ + WARN_ON_ONCE(rcu_irq_enter_disabled()),\ rcu_irq_enter_irqson(), \ rcu_irq_exit_irqson()); \ } @@ -186,7 +189,7 @@ extern void syscall_unregfunc(void); __DO_TRACE(&__tracepoint_##name, \ TP_PROTO(data_proto), \ TP_ARGS(data_args), \ - TP_CONDITION(cond),,); \ + TP_CONDITION(cond),0,,); \ if (IS_ENABLED(CONFIG_LOCKDEP) && (cond)) { \ rcu_read_lock_sched_notrace(); \ rcu_dereference_sched(__tracepoint_##name.funcs);\ -- 2.9.3
