trace-cmd: Plug startup race between flush_threads and recorders

As the SIGUSR1 handler is so far registered after forking the recorder
child, there is a small race window where a flush sent by the main
process can actually kill the child. Plug this by registering the signal
handlers before the fork. This also allows to unify SIGINT registration.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
LKML-Reference: <4CB8401B.2020801@siemens.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 3 insertions, 4 deletions

diff --git a/trace-cmd.c b/trace-cmd.c
index 9cbe362..f8992a8 100644
--- a/trace-cmd.c
+++ b/trace-cmd.c
@@ -1089,6 +1089,8 @@ static int create_recorder(int cpu)
         char *file;
         int pid;
 
+        signal(SIGUSR1, flush);
+
         pid = fork();
         if (pid < 0)
                 die("fork");
@@ -1096,9 +1098,6 @@ static int create_recorder(int cpu)
         if (pid)
                 return pid;
 
-        signal(SIGINT, finish);
-        signal(SIGUSR1, flush);
-
         if (rt_prio)
                 set_prio(rt_prio);
 
@@ -1694,9 +1693,9 @@ int main (int argc, char **argv)
         set_options();
 
         if (record || extract) {
+                signal(SIGINT, finish);
                 if (!latency)
                         start_threads();
-                signal(SIGINT, finish);
         }
 
         if (extract) {