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From: Oleg Nesterov on 21 Mar 2010 14:50
Cleanup:

- Add the boolean, group_dead = thread_group_leader(), for clarity.

- Do not test/set sig == NULL to detect the all-dead case, use this
boolean.

- Pass this boolen to __unhash_process() and use it instead of another
thread_group_leader() call which needs ->group_leader.

This can be considered as microoptimization, but hopefully this also
allows us do do other cleanups later.

Signed-off-by: Oleg Nesterov <oleg(a)redhat.com>
---

kernel/exit.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)

--- 34-rc1/kernel/exit.c~11_EXIT_SIGNAL_CLEANUP_GROUP_DEAD 2010-03-19 19:17:53.000000000 +0100
+++ 34-rc1/kernel/exit.c 2010-03-21 18:34:02.000000000 +0100
@@ -59,11 +59,11 @@

static void exit_mm(struct task_struct * tsk);

-static void __unhash_process(struct task_struct *p)
+static void __unhash_process(struct task_struct *p, bool group_dead)
{
nr_threads--;
detach_pid(p, PIDTYPE_PID);
- if (thread_group_leader(p)) {
+ if (group_dead) {
detach_pid(p, PIDTYPE_PGID);
detach_pid(p, PIDTYPE_SID);

@@ -80,6 +80,7 @@ static void __unhash_process(struct task
static void __exit_signal(struct task_struct *tsk)
{
struct signal_struct *sig = tsk->signal;
+ bool group_dead = thread_group_leader(tsk);
struct sighand_struct *sighand;
struct tty_struct *tty;

@@ -93,7 +94,7 @@ static void __exit_signal(struct task_st
atomic_dec(&sig->count);

posix_cpu_timers_exit(tsk);
- if (thread_group_leader(tsk)) {
+ if (group_dead) {
posix_cpu_timers_exit_group(tsk);
tty = sig->tty;
sig->tty = NULL;
@@ -128,10 +129,9 @@ static void __exit_signal(struct task_st
sig->oublock += task_io_get_oublock(tsk);
task_io_accounting_add(&sig->ioac, &tsk->ioac);
sig->sum_sched_runtime += tsk->se.sum_exec_runtime;
- sig = NULL; /* Marker for below. */
}

- __unhash_process(tsk);
+ __unhash_process(tsk, group_dead);

/*
* Do this under ->siglock, we can race with another thread
@@ -143,7 +143,7 @@ static void __exit_signal(struct task_st

__cleanup_sighand(sighand);
clear_tsk_thread_flag(tsk,TIF_SIGPENDING);
- if (sig) {
+ if (group_dead) {
flush_sigqueue(&sig->shared_pending);
taskstats_tgid_free(sig);
tty_kref_put(tty);

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