[PATCH] do_sigaction: don't take tasklist_lock

do_sigaction() does not need tasklist_lock anymore, we can simplify the code.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 3 insertions, 19 deletions

diff --git a/kernel/signal.c b/kernel/signal.c
index e3bdec914626..2dfaa5076c31 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2301,8 +2301,7 @@ sys_rt_sigqueueinfo(int pid, int sig, siginfo_t __user *uinfo)
         return kill_proc_info(sig, &info, pid);
 }
 
-int
-do_sigaction(int sig, struct k_sigaction *act, struct k_sigaction *oact)
+int do_sigaction(int sig, struct k_sigaction *act, struct k_sigaction *oact)
 {
         struct k_sigaction *k;
         sigset_t mask;
@@ -2328,6 +2327,7 @@ do_sigaction(int sig, struct k_sigaction *act, struct k_sigaction *oact)
         if (act) {
                 sigdelsetmask(&act->sa.sa_mask,
                               sigmask(SIGKILL) | sigmask(SIGSTOP));
+                *k = *act;
                 /*
                  * POSIX 3.3.1.3:
                  *  "Setting a signal action to SIG_IGN for a signal that is
@@ -2340,19 +2340,8 @@ do_sigaction(int sig, struct k_sigaction *act, struct k_sigaction *oact)
                  *   be discarded, whether or not it is blocked"
                  */
                 if (act->sa.sa_handler == SIG_IGN ||
-                    (act->sa.sa_handler == SIG_DFL &&
-                     sig_kernel_ignore(sig))) {
-                        /*
-                         * This is a fairly rare case, so we only take the
-                         * tasklist_lock once we're sure we'll need it.
-                         * Now we must do this little unlock and relock
-                         * dance to maintain the lock hierarchy.
-                         */
+                   (act->sa.sa_handler == SIG_DFL && sig_kernel_ignore(sig))) {
                         struct task_struct *t = current;
-                        spin_unlock_irq(&t->sighand->siglock);
-                        read_lock(&tasklist_lock);
-                        spin_lock_irq(&t->sighand->siglock);
-                        *k = *act;
                         sigemptyset(&mask);
                         sigaddset(&mask, sig);
                         rm_from_queue_full(&mask, &t->signal->shared_pending);
@@ -2361,12 +2350,7 @@ do_sigaction(int sig, struct k_sigaction *act, struct k_sigaction *oact)
                                 recalc_sigpending_tsk(t);
                                 t = next_thread(t);
                         } while (t != current);
-                        spin_unlock_irq(&current->sighand->siglock);
-                        read_unlock(&tasklist_lock);
-                        return 0;
                 }
-
-                *k = *act;
         }
 
         spin_unlock_irq(&current->sighand->siglock);