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| author | Li Zefan <lizf@cn.fujitsu.com> | 2010-08-23 16:50:12 +0800 |
|---|---|---|
| committer | Steven Rostedt <rostedt@goodmis.org> | 2010-08-31 16:46:23 -0400 |
| commit | 3aaba20f26f58843e8f20611e5c0b1c06954310f (patch) | |
| tree | ad15d7aa21af465ddf6091eb490d84312089f245 /kernel | |
| parent | fa66f07aa1f0950e1dc78b7ab39728b3f8aa77a1 (diff) | |
| download | linux-3aaba20f26f58843e8f20611e5c0b1c06954310f.tar.gz linux-3aaba20f26f58843e8f20611e5c0b1c06954310f.tar.bz2 linux-3aaba20f26f58843e8f20611e5c0b1c06954310f.zip | |
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>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/trace/ftrace.c | 15 |
1 files changed, 11 insertions, 4 deletions
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 0d88ce9b9fb8..7cb1f45a1de1 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) |