ITIMER_REAL: convert to use struct pid

signal_struct->tsk points to the ->group_leader and thus we have the nasty
code in de_thread() which has to change it and restart ->real_timer if the
leader is changed.

Use "struct pid *leader_pid" instead.  This also allows us to kill now
unneeded send_group_sig_info().

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Davide Libenzi <davidel@xmailserver.org>
Cc: Pavel Emelyanov <xemul@openvz.org>
Acked-by: Roland McGrath <roland@redhat.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

5 files changed, 5 insertions, 38 deletions

diff --git a/fs/exec.c b/fs/exec.c
index be923e4bc389..927a7c5ef4af 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -782,26 +782,8 @@ static int de_thread(struct task_struct *tsk)
         zap_other_threads(tsk);
         read_unlock(&tasklist_lock);
 
-        /*
-         * Account for the thread group leader hanging around:
-         */
-        count = 1;
-        if (!thread_group_leader(tsk)) {
-                count = 2;
-                /*
-                 * The SIGALRM timer survives the exec, but needs to point
-                 * at us as the new group leader now.  We have a race with
-                 * a timer firing now getting the old leader, so we need to
-                 * synchronize with any firing (by calling del_timer_sync)
-                 * before we can safely let the old group leader die.
-                 */
-                sig->tsk = tsk;
-                spin_unlock_irq(lock);
-                if (hrtimer_cancel(&sig->real_timer))
-                        hrtimer_restart(&sig->real_timer);
-                spin_lock_irq(lock);
-        }
-
+        /* Account for the thread group leader hanging around: */
+        count = thread_group_leader(tsk) ? 1 : 2;
         sig->notify_count = count;
         while (atomic_read(&sig->count) > count) {
                 __set_current_state(TASK_UNINTERRUPTIBLE);
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 3deb6e5d3096..b2d161d87db7 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -460,7 +460,7 @@ struct signal_struct {
 
         /* ITIMER_REAL timer for the process */
         struct hrtimer real_timer;
-        struct task_struct *tsk;
+        struct pid *leader_pid;
         ktime_t it_real_incr;
 
         /* ITIMER_PROF and ITIMER_VIRTUAL timers for the process */
@@ -1686,7 +1686,6 @@ extern void block_all_signals(int (*notifier)(void *priv), void *priv,
 extern void unblock_all_signals(void);
 extern void release_task(struct task_struct * p);
 extern int send_sig_info(int, struct siginfo *, struct task_struct *);
-extern int send_group_sig_info(int, struct siginfo *, struct task_struct *);
 extern int force_sigsegv(int, struct task_struct *);
 extern int force_sig_info(int, struct siginfo *, struct task_struct *);
 extern int __kill_pgrp_info(int sig, struct siginfo *info, struct pid *pgrp);
diff --git a/kernel/fork.c b/kernel/fork.c
index b2ef8e4fad70..ca54d9704644 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -909,7 +909,6 @@ static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
         sig->it_real_incr.tv64 = 0;
         sig->real_timer.function = it_real_fn;
-        sig->tsk = tsk;
 
         sig->it_virt_expires = cputime_zero;
         sig->it_virt_incr = cputime_zero;
@@ -1338,6 +1337,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
                         if (clone_flags & CLONE_NEWPID)
                                 p->nsproxy->pid_ns->child_reaper = p;
 
+                        p->signal->leader_pid = pid;
                         p->signal->tty = current->signal->tty;
                         set_task_pgrp(p, task_pgrp_nr(current));
                         set_task_session(p, task_session_nr(current));
diff --git a/kernel/itimer.c b/kernel/itimer.c
index 2fab344dbf56..ab982747d9bd 100644
--- a/kernel/itimer.c
+++ b/kernel/itimer.c
@@ -132,7 +132,7 @@ enum hrtimer_restart it_real_fn(struct hrtimer *timer)
         struct signal_struct *sig =
                 container_of(timer, struct signal_struct, real_timer);
 
-        send_group_sig_info(SIGALRM, SEND_SIG_PRIV, sig->tsk);
+        kill_pid_info(SIGALRM, SEND_SIG_PRIV, sig->leader_pid);
 
         return HRTIMER_NORESTART;
 }
diff --git a/kernel/signal.c b/kernel/signal.c
index b0b43a4ad8dd..cc45a6b69134 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1205,20 +1205,6 @@ send_sig(int sig, struct task_struct *p, int priv)
         return send_sig_info(sig, __si_special(priv), p);
 }
 
-/*
- * This is the entry point for "process-wide" signals.
- * They will go to an appropriate thread in the thread group.
- */
-int
-send_group_sig_info(int sig, struct siginfo *info, struct task_struct *p)
-{
-        int ret;
-        read_lock(&tasklist_lock);
-        ret = group_send_sig_info(sig, info, p);
-        read_unlock(&tasklist_lock);
-        return ret;
-}
-
 void
 force_sig(int sig, struct task_struct *p)
 {