[PATCH] do_sigaction: don't take tasklist_lock
Oleg Nesterov [Wed, 29 Mar 2006 00:11:24 +0000 (16:11 -0800)]
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>

kernel/signal.c

index e3bdec9..2dfaa50 100644 (file)
@@ -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);