linux-kernel - [PATCH 7/5] tracing: Make sure rcu_irq_enter() can work for trace_*

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Message-ID: <20170407130615.2309b96d@gandalf.local.home>
Date:   Fri, 7 Apr 2017 13:06:15 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     linux-kernel@...r.kernel.org
Cc:     Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: [PATCH 7/5] tracing: Make sure rcu_irq_enter() can work for
 trace_*_rcuidle() trace events

From: "Steven Rostedt (VMware)" <rostedt@...dmis.org>

Stack tracing discovered that there's a small location inside the RCU
infrastructure that 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.

Cc: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
---
 include/linux/tracepoint.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index f72fcfe..8baef96 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -159,6 +159,8 @@ extern void syscall_unregfunc(void);
 				TP_PROTO(data_proto),			\
 				TP_ARGS(data_args),			\
 				TP_CONDITION(cond),			\
+				if (WARN_ON_ONCE(rcu_irq_enter_disabled())) \
+					return;				\
 				rcu_irq_enter_irqson(),			\
 				rcu_irq_exit_irqson());			\
 	}
-- 
2.9.3