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Groups > linux.kernel > #1441577

[PATCH RT 6/8] trace: correct off by one while recording the trace-event

From Steven Rostedt <rostedt@goodmis.org>
Newsgroups linux.kernel
Subject [PATCH RT 6/8] trace: correct off by one while recording the trace-event
Date 2016-07-12 19:00 +0200
Message-ID <rU9cm-7AG-43@gated-at.bofh.it> (permalink)
References <rU9cm-7AG-21@gated-at.bofh.it>
Organization linux.* mail to news gateway

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3.10.102-rt113-rc1 stable review patch.
If anyone has any objections, please let me know.

------------------

From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

Trace events like raw_syscalls show always a preempt code of one. The
reason is that on PREEMPT kernels rcu_read_lock_sched_notrace()
increases the preemption counter and the function recording the counter
is caller within the RCU section.

Cc: stable-rt@vger.kernel.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
[ Changed this to upstream version. See commit e947841c0dce ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 include/trace/ftrace.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h
index dbb47418df81..f30e85b675e8 100644
--- a/include/trace/ftrace.h
+++ b/include/trace/ftrace.h
@@ -526,6 +526,9 @@ ftrace_raw_event_##call(void *__data, proto)				\
 									\
 	local_save_flags(irq_flags);					\
 	pc = preempt_count();						\
+	/* Account for tracepoint preempt disable */			\
+	if (IS_ENABLED(CONFIG_PREEMPT))					\
+		pc--;							\
 									\
 	__data_size = ftrace_get_offsets_##call(&__data_offsets, args); \
 									\
-- 
2.8.1

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Thread

[PATCH RT 0/8] Linux 3.10.102-rt113-rc1 Steven Rostedt <rostedt@goodmis.org> - 2016-07-12 19:00 +0200
  [PATCH RT 8/8] Linux 3.10.102-rt113-rc1 Steven Rostedt <rostedt@goodmis.org> - 2016-07-12 19:00 +0200
  [PATCH RT 6/8] trace: correct off by one while recording the trace-event Steven Rostedt <rostedt@goodmis.org> - 2016-07-12 19:00 +0200
  [PATCH RT 4/8] kernel/printk: Dont try to print from IRQ/NMI region Steven Rostedt <rostedt@goodmis.org> - 2016-07-12 19:00 +0200
  [PATCH RT 3/8] list_bl: fixup bogus lockdep warning Steven Rostedt <rostedt@goodmis.org> - 2016-07-12 19:00 +0200
  [PATCH RT 7/8] x86: Fix an RT MCE crash Steven Rostedt <rostedt@goodmis.org> - 2016-07-12 19:10 +0200
  [PATCH RT 1/8] kvm, rt: change async pagefault code locking for PREEMPT_RT Steven Rostedt <rostedt@goodmis.org> - 2016-07-12 19:10 +0200

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