linux-kernel - [PATCH] ftrace, sched: Add TRACE_FLAG_PREEMPT

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Date:	Fri, 27 Sep 2013 17:29:08 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Yuanhan Liu <yuanhan.liu@...ux.intel.com>
Cc:	mingo@...nel.org, hpa@...or.com, linux-kernel@...r.kernel.org,
	tglx@...utronix.de, linux-tip-commits@...r.kernel.org,
	Fengguang Wu <fengguang.wu@...el.com>,
	Huang Ying <ying.huang@...el.com>, lkp@...ux.intel.com,
	Steven Rostedt <rostedt@...dmis.org>
Subject: [PATCH] ftrace, sched: Add TRACE_FLAG_PREEMPT_RESCHED

Subject: ftrace, sched: Add TRACE_FLAG_PREEMPT_RESCHED
From: Peter Zijlstra <peterz@...radead.org>
Date: Fri Sep 27 17:11:00 CEST 2013

Since we now have two need_resched states; trace the two so we can
observe discrepancies.

Cc: Steven Rostedt <rostedt@...dmis.org>
Signed-off-by: Peter Zijlstra <peterz@...radead.org>
---
 kernel/trace/trace.c        |    3 ++-
 kernel/trace/trace.h        |    1 +
 kernel/trace/trace_output.c |   13 +++++++++++--
 3 files changed, 14 insertions(+), 3 deletions(-)

--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1509,7 +1509,8 @@ tracing_generic_entry_update(struct trac
 #endif
 		((pc & HARDIRQ_MASK) ? TRACE_FLAG_HARDIRQ : 0) |
 		((pc & SOFTIRQ_MASK) ? TRACE_FLAG_SOFTIRQ : 0) |
-		(need_resched() ? TRACE_FLAG_NEED_RESCHED : 0);
+		(tif_need_resched() ? TRACE_FLAG_NEED_RESCHED : 0) |
+		(test_preempt_need_resched() ? TRACE_FLAG_PREEMPT_RESCHED : 0);
 }
 EXPORT_SYMBOL_GPL(tracing_generic_entry_update);
 
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -124,6 +124,7 @@ enum trace_flag_type {
 	TRACE_FLAG_NEED_RESCHED		= 0x04,
 	TRACE_FLAG_HARDIRQ		= 0x08,
 	TRACE_FLAG_SOFTIRQ		= 0x10,
+	TRACE_FLAG_PREEMPT_RESCHED	= 0x20,
 };
 
 #define TRACE_BUF_SIZE		1024
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -618,8 +618,17 @@ int trace_print_lat_fmt(struct trace_seq
 		(entry->flags & TRACE_FLAG_IRQS_OFF) ? 'd' :
 		(entry->flags & TRACE_FLAG_IRQS_NOSUPPORT) ? 'X' :
 		'.';
-	need_resched =
-		(entry->flags & TRACE_FLAG_NEED_RESCHED) ? 'N' : '.';
+
+	if ((entry->flags & TRACE_FLAG_NEED_RESCHED) &&
+	    (entry->flags & TRACE_FLAG_PREEMPT_RESCHED))
+		need_resched = 'N';
+	else if (entry->flags & TRACE_FLAG_NEED_RESCHED)
+		need_resched = 'n';
+	else if (entry->flags & TRACE_FLAG_PREEMPT_RESCHED)
+		need_resched = 'p';
+	else
+		need_resched = '.';
+
 	hardsoft_irq =
 		(hardirq && softirq) ? 'H' :
 		hardirq ? 'h' :
--
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