From: "Steven Rostedt (Red Hat)" With the conversion of the saved_cmdlines output to use seq_read, there is now a race between accessing the values of the saved_cmdlines and the writing to them. The trace_cmdline_lock needs to be taken at the start and stop of the seq calls. A new __trace_find_cmdline() call is created to allow for the look up to happen without taking the lock. Fixes: 42584c81c5ad tracing: Have saved_cmdlines use the seq_read infrastructure Signed-off-by: Steven Rostedt --- kernel/trace/trace.c | 19 +++++++++++++++---- 1 file changed, 15 insertions(+), 4 deletions(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 22a902e2ded9..626dbfde5d56 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -1484,7 +1484,7 @@ static int trace_save_cmdline(struct task_struct *tsk) return 1; } -void trace_find_cmdline(int pid, char comm[]) +static void __trace_find_cmdline(int pid, char comm[]) { unsigned map; @@ -1503,13 +1503,19 @@ void trace_find_cmdline(int pid, char comm[]) return; } - preempt_disable(); - arch_spin_lock(&trace_cmdline_lock); map = map_pid_to_cmdline[pid]; if (map != NO_CMDLINE_MAP) strcpy(comm, saved_cmdlines[map]); else strcpy(comm, "<...>"); +} + +void trace_find_cmdline(int pid, char comm[]) +{ + preempt_disable(); + arch_spin_lock(&trace_cmdline_lock); + + __trace_find_cmdline(pid, comm); arch_spin_unlock(&trace_cmdline_lock); preempt_enable(); @@ -3724,6 +3730,9 @@ static void *saved_cmdlines_start(struct seq_file *m, loff_t *pos) void *v; loff_t l = 0; + preempt_disable(); + arch_spin_lock(&trace_cmdline_lock); + v = &map_cmdline_to_pid[0]; while (l <= *pos) { v = saved_cmdlines_next(m, v, &l); @@ -3736,6 +3745,8 @@ static void *saved_cmdlines_start(struct seq_file *m, loff_t *pos) static void saved_cmdlines_stop(struct seq_file *m, void *v) { + arch_spin_unlock(&trace_cmdline_lock); + preempt_enable(); } static int saved_cmdlines_show(struct seq_file *m, void *v) @@ -3743,7 +3754,7 @@ static int saved_cmdlines_show(struct seq_file *m, void *v) char buf[TASK_COMM_LEN]; unsigned int *pid = v; - trace_find_cmdline(*pid, buf); + __trace_find_cmdline(*pid, buf); seq_printf(m, "%d %s\n", *pid, buf); return 0; } -- 2.0.0.rc2