Changes:
s/tgrp/thread_group/
make it rcu-safe
[PATCH rc5-mm] pids: kill PIDTYPE_TGID
depends on pidhash-dont-count-idle-threads.patch
This patch kills PIDTYPE_TGID pid_type thus saving one hash table
in kernel/pid.c and speeding up subthreads create/destroy a bit.
It is also a preparation for the further tref/pids rework.
This patch adds 'struct list_head thread_group' to 'struct task_struct'
instead.
We don't detach group leader from PIDTYPE_PID namespace until another
thread inherits it's ->pid == ->tgid, so we are safe wrt premature
free_pidmap(->tgid) call.
Currently there are no users of find_task_by_pid_type(PIDTYPE_TGID).
Should the need arise, we can use find_task_by_pid()->group_leader.
include/linux/pid.h | 1 -
include/linux/sched.h | 10 +++++++---
kernel/exit.c | 10 +---------
kernel/fork.c | 4 +++-
4 files changed, 11 insertions(+), 14 deletions(-)
Signed-off-by: Oleg Nesterov <[email protected]>
--- 2.6.16-rc5/include/linux/pid.h~1_TGID 2006-03-09 00:17:24.000000000 +0300
+++ 2.6.16-rc5/include/linux/pid.h 2006-03-09 00:20:45.000000000 +0300
@@ -4,7 +4,6 @@
enum pid_type
{
PIDTYPE_PID,
- PIDTYPE_TGID,
PIDTYPE_PGID,
PIDTYPE_SID,
PIDTYPE_MAX
--- 2.6.16-rc5/include/linux/sched.h~1_TGID 2006-03-09 00:17:24.000000000 +0300
+++ 2.6.16-rc5/include/linux/sched.h 2006-03-09 00:34:57.000000000 +0300
@@ -748,6 +748,7 @@ struct task_struct {
/* PID/PID hash table linkage. */
struct pid pids[PIDTYPE_MAX];
+ struct list_head thread_group;
struct completion *vfork_done; /* for vfork() */
int __user *set_child_tid; /* CLONE_CHILD_SETTID */
@@ -1181,13 +1182,17 @@ extern void wait_task_inactive(task_t *
#define while_each_thread(g, t) \
while ((t = next_thread(t)) != g)
-extern task_t * FASTCALL(next_thread(const task_t *p));
-
#define thread_group_leader(p) (p->pid == p->tgid)
+static inline task_t *next_thread(task_t *p)
+{
+ return list_entry(rcu_dereference(p->thread_group.next),
+ task_t, thread_group);
+}
+
static inline int thread_group_empty(task_t *p)
{
- return list_empty(&p->pids[PIDTYPE_TGID].pid_list);
+ return list_empty(&p->thread_group);
}
#define delay_group_leader(p) \
--- 2.6.16-rc5/kernel/exit.c~1_TGID 2006-03-09 00:17:24.000000000 +0300
+++ 2.6.16-rc5/kernel/exit.c 2006-03-09 00:42:26.000000000 +0300
@@ -49,7 +49,6 @@ static void __unhash_process(struct task
{
nr_threads--;
detach_pid(p, PIDTYPE_PID);
- detach_pid(p, PIDTYPE_TGID);
if (thread_group_leader(p)) {
detach_pid(p, PIDTYPE_PGID);
detach_pid(p, PIDTYPE_SID);
@@ -57,7 +56,7 @@ static void __unhash_process(struct task
list_del_init(&p->tasks);
__get_cpu_var(process_counts)--;
}
-
+ list_del_rcu(&p->thread_group);
remove_parent(p);
}
@@ -953,13 +952,6 @@ asmlinkage long sys_exit(int error_code)
do_exit((error_code&0xff)<<8);
}
-task_t fastcall *next_thread(const task_t *p)
-{
- return pid_task(p->pids[PIDTYPE_TGID].pid_list.next, PIDTYPE_TGID);
-}
-
-EXPORT_SYMBOL(next_thread);
-
/*
* Take down every thread in the group. This is called by fatal signals
* as well as by sys_exit_group (below).
--- 2.6.16-rc5/kernel/fork.c~1_TGID 2006-03-09 00:17:24.000000000 +0300
+++ 2.6.16-rc5/kernel/fork.c 2006-03-09 00:41:35.000000000 +0300
@@ -1100,6 +1100,7 @@ static task_t *copy_process(unsigned lon
* We dont wake it up yet.
*/
p->group_leader = p;
+ INIT_LIST_HEAD(&p->thread_group);
INIT_LIST_HEAD(&p->ptrace_children);
INIT_LIST_HEAD(&p->ptrace_list);
@@ -1153,7 +1154,9 @@ static task_t *copy_process(unsigned lon
retval = -EAGAIN;
goto bad_fork_cleanup_namespace;
}
+
p->group_leader = current->group_leader;
+ list_add_tail_rcu(&p->thread_group, ¤t->thread_group);
if (current->signal->group_stop_count > 0) {
/*
@@ -1201,7 +1204,6 @@ static task_t *copy_process(unsigned lon
list_add_tail(&p->tasks, &init_task.tasks);
__get_cpu_var(process_counts)++;
}
- attach_pid(p, PIDTYPE_TGID, p->tgid);
attach_pid(p, PIDTYPE_PID, p->pid);
nr_threads++;
}
-
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