exit: __exit_signal: use thread_group_leader() consistently

Cleanup:

- Add the boolean, group_dead = thread_group_leader(), for clarity.

- Do not test/set sig == NULL to detect the all-dead case, use this
  boolean.

- Pass this boolen to __unhash_process() and use it instead of another
  thread_group_leader() call which needs ->group_leader.

  This can be considered as microoptimization, but hopefully this also
  allows us do do other cleanups later.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Cc: Roland McGrath <roland@redhat.com>
Cc: Veaceslav Falico <vfalico@redhat.com>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 6 deletions

diff --git a/kernel/exit.c b/kernel/exit.c
index bbc790646502..3602f468e3a0 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -58,11 +58,11 @@
 
 static void exit_mm(struct task_struct * tsk);
 
-static void __unhash_process(struct task_struct *p)
+static void __unhash_process(struct task_struct *p, bool group_dead)
 {
         nr_threads--;
         detach_pid(p, PIDTYPE_PID);
-        if (thread_group_leader(p)) {
+        if (group_dead) {
                 detach_pid(p, PIDTYPE_PGID);
                 detach_pid(p, PIDTYPE_SID);
 
@@ -79,6 +79,7 @@ static void __unhash_process(struct task_struct *p)
 static void __exit_signal(struct task_struct *tsk)
 {
         struct signal_struct *sig = tsk->signal;
+        bool group_dead = thread_group_leader(tsk);
         struct sighand_struct *sighand;
         struct tty_struct *uninitialized_var(tty);
 
@@ -92,7 +93,7 @@ static void __exit_signal(struct task_struct *tsk)
         atomic_dec(&sig->count);
 
         posix_cpu_timers_exit(tsk);
-        if (thread_group_leader(tsk)) {
+        if (group_dead) {
                 posix_cpu_timers_exit_group(tsk);
                 tty = sig->tty;
                 sig->tty = NULL;
@@ -127,10 +128,9 @@ static void __exit_signal(struct task_struct *tsk)
                 sig->oublock += task_io_get_oublock(tsk);
                 task_io_accounting_add(&sig->ioac, &tsk->ioac);
                 sig->sum_sched_runtime += tsk->se.sum_exec_runtime;
-                sig = NULL; /* Marker for below. */
         }
 
-        __unhash_process(tsk);
+        __unhash_process(tsk, group_dead);
 
         /*
          * Do this under ->siglock, we can race with another thread
@@ -142,7 +142,7 @@ static void __exit_signal(struct task_struct *tsk)
 
         __cleanup_sighand(sighand);
         clear_tsk_thread_flag(tsk,TIF_SIGPENDING);
-        if (sig) {
+        if (group_dead) {
                 flush_sigqueue(&sig->shared_pending);
                 taskstats_tgid_free(sig);
                 tty_kref_put(tty);