tracing: fix trace_find_cmdline()

Impact: prevent stale command line output

In case there is no valid command line mapping for a pid
trace_find_cmdline() returns without updating the comm buffer. The
trace dump keeps the previous entry which results in confusing trace
output:

     <idle>-0     [000]   280.702056 ....
     <idle>-23456 [000]   280.702080 ....

Update the comm buffer with "<...>" when no mapping is found.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Steven Rostedt <srostedt@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 4 insertions, 5 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index ca673c475687..06c69a260328 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -787,12 +787,11 @@ void trace_find_cmdline(int pid, char comm[])
 
         __raw_spin_lock(&trace_cmdline_lock);
         map = map_pid_to_cmdline[pid];
-        if (map == NO_CMDLINE_MAP)
-                goto out;
-
-        strcpy(comm, saved_cmdlines[map]);
+        if (map != NO_CMDLINE_MAP)
+                strcpy(comm, saved_cmdlines[map]);
+        else
+                strcpy(comm, "<...>");
 
- out:
         __raw_spin_unlock(&trace_cmdline_lock);
 }