[PATCH] RCU signal handling
RCU tasklist_lock and RCU signal handling: send signals RCU-read-locked
instead of tasklist_lock read-locked. This is a scalability improvement on
SMP and a preemption-latency improvement under PREEMPT_RCU.
Signed-off-by: Paul E. McKenney <paulmck@us.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Acked-by: William Irwin <wli@holomorphy.com>
Cc: Roland McGrath <roland@redhat.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/kernel/pid.c b/kernel/pid.c
index edba31c..1acc072 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -136,7 +136,7 @@
struct hlist_node *elem;
struct pid *pid;
- hlist_for_each_entry(pid, elem,
+ hlist_for_each_entry_rcu(pid, elem,
&pid_hash[type][pid_hashfn(nr)], pid_chain) {
if (pid->nr == nr)
return pid;
@@ -150,15 +150,15 @@
task_pid = &task->pids[type];
pid = find_pid(type, nr);
+ task_pid->nr = nr;
if (pid == NULL) {
- hlist_add_head(&task_pid->pid_chain,
- &pid_hash[type][pid_hashfn(nr)]);
INIT_LIST_HEAD(&task_pid->pid_list);
+ hlist_add_head_rcu(&task_pid->pid_chain,
+ &pid_hash[type][pid_hashfn(nr)]);
} else {
INIT_HLIST_NODE(&task_pid->pid_chain);
- list_add_tail(&task_pid->pid_list, &pid->pid_list);
+ list_add_tail_rcu(&task_pid->pid_list, &pid->pid_list);
}
- task_pid->nr = nr;
return 0;
}
@@ -170,20 +170,20 @@
pid = &task->pids[type];
if (!hlist_unhashed(&pid->pid_chain)) {
- hlist_del(&pid->pid_chain);
- if (list_empty(&pid->pid_list))
+ if (list_empty(&pid->pid_list)) {
nr = pid->nr;
- else {
+ hlist_del_rcu(&pid->pid_chain);
+ } else {
pid_next = list_entry(pid->pid_list.next,
struct pid, pid_list);
/* insert next pid from pid_list to hash */
- hlist_add_head(&pid_next->pid_chain,
- &pid_hash[type][pid_hashfn(pid_next->nr)]);
+ hlist_replace_rcu(&pid->pid_chain,
+ &pid_next->pid_chain);
}
}
- list_del(&pid->pid_list);
+ list_del_rcu(&pid->pid_list);
pid->nr = 0;
return nr;
