On Fri, 7 Dec 2007, Oleg Nesterov wrote:
> 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 <[email protected]>
Nice cleanup.
Acked-by: Thomas Gleixner <[email protected]>
> include/linux/sched.h | 3 +--
> kernel/fork.c | 2 +-
> kernel/itimer.c | 2 +-
> fs/exec.c | 22 ++--------------------
> kernel/signal.c | 14 --------------
> 5 files changed, 5 insertions(+), 38 deletions(-)
>
> --- PT/include/linux/sched.h~3_itimer_tsk_pid 2007-12-02 14:53:29.000000000 +0300
> +++ PT/include/linux/sched.h 2007-12-07 19:24:44.000000000 +0300
> @@ -444,7 +444,7 @@ 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 */
> @@ -1630,7 +1630,6 @@ extern void block_all_signals(int (*noti
> 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);
> --- PT/kernel/fork.c~3_itimer_tsk_pid 2007-12-07 19:03:34.000000000 +0300
> +++ PT/kernel/fork.c 2007-12-07 19:08:57.000000000 +0300
> @@ -882,7 +882,6 @@ static int copy_signal(unsigned long clo
> 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;
> @@ -1300,6 +1299,7 @@ static struct task_struct *copy_process(
> 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));
> --- PT/kernel/itimer.c~3_itimer_tsk_pid 2007-10-25 16:22:12.000000000 +0400
> +++ PT/kernel/itimer.c 2007-12-07 19:15:27.000000000 +0300
> @@ -132,7 +132,7 @@ enum hrtimer_restart it_real_fn(struct h
> 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;
> }
> --- PT/fs/exec.c~3_itimer_tsk_pid 2007-12-02 16:07:22.000000000 +0300
> +++ PT/fs/exec.c 2007-12-07 19:18:48.000000000 +0300
> @@ -781,26 +781,8 @@ static int de_thread(struct task_struct
> 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);
> --- PT/kernel/signal.c~3_itimer_tsk_pid 2007-12-07 17:20:27.000000000 +0300
> +++ PT/kernel/signal.c 2007-12-07 19:23:40.000000000 +0300
> @@ -1204,20 +1204,6 @@ send_sig(int sig, struct task_struct *p,
> 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)
> {
>
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