linux-kernel - [RFC PATCH 05/10] ftrace: Drop buffer check in function profiler callbacks

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Date:	Fri, 22 Jan 2010 02:16:17 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Li Zefan <lizf@...fujitsu.com>,
	Lai Jiangshan <laijs@...fujitsu.com>
Subject: [RFC PATCH 05/10] ftrace: Drop buffer check in function profiler callbacks

Drop the null check on hlist->hash. It is wasteful because
we don't register the tracer if the buffer allocation failed,
and the memory barrier in register_ftrace_graph() ensure it
is visible to the callbacks right away.

Also we know the tracing callbacks won't be called after
register_ftrace_graph(), so subsequent buffer resets are safe
too.

Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Li Zefan <lizf@...fujitsu.com>
Cc: Lai Jiangshan <laijs@...fujitsu.com>
---
 kernel/trace/ftrace.c |    5 -----
 1 files changed, 0 insertions(+), 5 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 3cdb35e..dfd8f7c 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -384,8 +384,6 @@ function_profile_call(unsigned long ip, unsigned long parent_ip)
 	local_irq_save(flags);
 
 	hlist = &__get_cpu_var(func_hlist_cpu);
-	if (!hlist->hash)
-		goto out;
 
 	rec = function_find_hlist_node(hlist, ip);
 	if (!rec) {
@@ -415,8 +413,6 @@ static void profile_graph_return(struct ftrace_graph_ret *trace)
 
 	local_irq_save(flags);
 	hlist = &__get_cpu_var(func_hlist_cpu);
-	if (!hlist->hash)
-		goto out;
 
 	calltime = trace->rettime - trace->calltime;
 
@@ -439,7 +435,6 @@ static void profile_graph_return(struct ftrace_graph_ret *trace)
 	if (rec)
 		rec->time += calltime;
 
- out:
 	local_irq_restore(flags);
 }
 
-- 
1.6.2.3

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