kill_pid_info: don't take now unneeded tasklist_lock

Previously handle_stop_signal(SIGCONT) could drop ->siglock.  That is why
kill_pid_info(SIGCONT) takes tasklist_lock to make sure the target task can't
go away after unlock.  Not needed now.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Roland McGrath <roland@redhat.com>
Cc: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 1 insertions, 8 deletions

diff --git a/include/linux/signal.h b/include/linux/signal.h
index 42d2e0a948f4..84f997f8aa53 100644
--- a/include/linux/signal.h
+++ b/include/linux/signal.h
@@ -362,8 +362,6 @@ int unhandled_signal(struct task_struct *tsk, int sig);
 #define sig_kernel_stop(sig) \
         (((sig) < SIGRTMIN) && siginmask(sig, SIG_KERNEL_STOP_MASK))
 
-#define sig_needs_tasklist(sig) ((sig) == SIGCONT)
-
 #define sig_user_defined(t, signr) \
         (((t)->sighand->action[(signr)-1].sa.sa_handler != SIG_DFL) &&  \
          ((t)->sighand->action[(signr)-1].sa.sa_handler != SIG_IGN))
diff --git a/kernel/signal.c b/kernel/signal.c
index 115c04f3f143..ce53ab19c21d 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1039,9 +1039,6 @@ int kill_pid_info(int sig, struct siginfo *info, struct pid *pid)
         struct task_struct *p;
 
         rcu_read_lock();
-        if (unlikely(sig_needs_tasklist(sig)))
-                read_lock(&tasklist_lock);
-
 retry:
         p = pid_task(pid, PIDTYPE_PID);
         if (p) {
@@ -1055,10 +1052,8 @@ retry:
                          */
                         goto retry;
         }
-
-        if (unlikely(sig_needs_tasklist(sig)))
-                read_unlock(&tasklist_lock);
         rcu_read_unlock();
+
         return error;
 }