lkml.org 
[lkml]   [2010]   [Aug]   [31]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Subject[PATCH v2][GIT PULL][v2.6.36] tracing: Fix a race in function profile
From
Date
Ingo,

Please pull this version instead. The only difference is that I Cc'd the
stable list.

Thanks,

-- Steve

Please pull the latest tip/perf/urgent-2 tree, which can be found at:

git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-2.6-trace.git
tip/perf/urgent-2


Li Zefan (1):
tracing: Fix a race in function profile

----
kernel/trace/ftrace.c | 15 +++++++++++----
1 files changed, 11 insertions(+), 4 deletions(-)
---------------------------
commit 3aaba20f26f58843e8f20611e5c0b1c06954310f
Author: Li Zefan <lizf@cn.fujitsu.com>
Date: Mon Aug 23 16:50:12 2010 +0800

tracing: Fix a race in function profile

While we are reading trace_stat/functionX and someone just
disabled function_profile at that time, we can trigger this:

divide error: 0000 [#1] PREEMPT SMP
...
EIP is at function_stat_show+0x90/0x230
...

This fix just takes the ftrace_profile_lock and checks if
rec->counter is 0. If it's 0, we know the profile buffer
has been reset.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: stable@kernel.org
LKML-Reference: <4C723644.4040708@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 0d88ce9..7cb1f45 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -381,12 +381,19 @@ static int function_stat_show(struct seq_file *m, void *v)
{
struct ftrace_profile *rec = v;
char str[KSYM_SYMBOL_LEN];
+ int ret = 0;
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
- static DEFINE_MUTEX(mutex);
static struct trace_seq s;
unsigned long long avg;
unsigned long long stddev;
#endif
+ mutex_lock(&ftrace_profile_lock);
+
+ /* we raced with function_profile_reset() */
+ if (unlikely(rec->counter == 0)) {
+ ret = -EBUSY;
+ goto out;
+ }

kallsyms_lookup(rec->ip, NULL, NULL, NULL, str);
seq_printf(m, " %-30.30s %10lu", str, rec->counter);
@@ -408,7 +415,6 @@ static int function_stat_show(struct seq_file *m, void *v)
do_div(stddev, (rec->counter - 1) * 1000);
}

- mutex_lock(&mutex);
trace_seq_init(&s);
trace_print_graph_duration(rec->time, &s);
trace_seq_puts(&s, " ");
@@ -416,11 +422,12 @@ static int function_stat_show(struct seq_file *m, void *v)
trace_seq_puts(&s, " ");
trace_print_graph_duration(stddev, &s);
trace_print_seq(m, &s);
- mutex_unlock(&mutex);
#endif
seq_putc(m, '\n');
+out:
+ mutex_unlock(&ftrace_profile_lock);

- return 0;
+ return ret;
}

static void ftrace_profile_reset(struct ftrace_profile_stat *stat)



\
 
 \ /
  Last update: 2010-08-31 22:51    [W:0.043 / U:0.924 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site