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authorOleg Nesterov <oleg@tv-sign.ru>2006-03-28 16:11:07 -0800
committerLinus Torvalds <torvalds@g5.osdl.org>2006-03-28 18:36:41 -0800
commit73b9ebfe126a4a886ee46cbab637374d7024668a (patch)
treed7ba00d4ce76b49c1569334956cd196b35977a04
parentc97d98931ac52ef110b62d9b75c6a6f2bfbc1898 (diff)
downloadlinux-73b9ebfe126a4a886ee46cbab637374d7024668a.tar.bz2
[PATCH] pidhash: don't count idle threads
fork_idle() does unhash_process() just after copy_process(). Contrary, boot_cpu's idle thread explicitely registers itself for each pid_type with nr = 0. copy_process() already checks p->pid != 0 before process_counts++, I think we can just skip attach_pid() calls and job control inits for idle threads and kill unhash_process(). We don't need to cleanup ->proc_dentry in fork_idle() because with this patch idle threads are never hashed in kernel/pid.c:pid_hash[]. We don't need to hash pid == 0 in pidmap_init(). free_pidmap() is never called with pid == 0 arg, so it will never be reused. So it is still possible to use pid == 0 in any PIDTYPE_xxx namespace from kernel/pid.c's POV. However with this patch we don't hash pid == 0 for PIDTYPE_PID case. We still have have PIDTYPE_PGID/PIDTYPE_SID entries with pid == 0: /sbin/init and kernel threads which don't call daemonize(). Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r--arch/um/kernel/smp.c1
-rw-r--r--include/linux/sched.h2
-rw-r--r--kernel/exit.c18
-rw-r--r--kernel/fork.c35
-rw-r--r--kernel/pid.c10
5 files changed, 20 insertions, 46 deletions
diff --git a/arch/um/kernel/smp.c b/arch/um/kernel/smp.c
index c8d8d0ac1a7f..511116aebaf7 100644
--- a/arch/um/kernel/smp.c
+++ b/arch/um/kernel/smp.c
@@ -143,7 +143,6 @@ void smp_prepare_cpus(unsigned int maxcpus)
idle = idle_thread(cpu);
init_idle(idle, cpu);
- unhash_process(idle);
waittime = 200000000;
while (waittime-- && !cpu_isset(cpu, cpu_callin_map))
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 1f16fb1fea22..ddc0df7f8bf5 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1214,8 +1214,6 @@ static inline int thread_group_empty(task_t *p)
#define delay_group_leader(p) \
(thread_group_leader(p) && !thread_group_empty(p))
-extern void unhash_process(struct task_struct *p);
-
/*
* Protects ->fs, ->files, ->mm, ->ptrace, ->group_info, ->comm, keyring
* subscriptions and synchronises with wait4(). Also used in procfs. Also
diff --git a/kernel/exit.c b/kernel/exit.c
index f436a6bd3fb7..a94e1c31131b 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -56,8 +56,7 @@ static void __unhash_process(struct task_struct *p)
detach_pid(p, PIDTYPE_SID);
list_del_init(&p->tasks);
- if (p->pid)
- __get_cpu_var(process_counts)--;
+ __get_cpu_var(process_counts)--;
}
remove_parent(p);
@@ -118,21 +117,6 @@ repeat:
goto repeat;
}
-/* we are using it only for SMP init */
-
-void unhash_process(struct task_struct *p)
-{
- struct dentry *proc_dentry;
-
- spin_lock(&p->proc_lock);
- proc_dentry = proc_pid_unhash(p);
- write_lock_irq(&tasklist_lock);
- __unhash_process(p);
- write_unlock_irq(&tasklist_lock);
- spin_unlock(&p->proc_lock);
- proc_pid_flush(proc_dentry);
-}
-
/*
* This checks not only the pgrp, but falls back on the pid if no
* satisfactory pgrp is found. I dunno - gdb doesn't work correctly
diff --git a/kernel/fork.c b/kernel/fork.c
index 74c67629ee62..0c32e28cdc5f 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1181,25 +1181,26 @@ static task_t *copy_process(unsigned long clone_flags,
*/
p->ioprio = current->ioprio;
- add_parent(p);
- if (unlikely(p->ptrace & PT_PTRACED))
- __ptrace_link(p, current->parent);
-
- if (thread_group_leader(p)) {
- p->signal->tty = current->signal->tty;
- p->signal->pgrp = process_group(current);
- p->signal->session = current->signal->session;
- attach_pid(p, PIDTYPE_PGID, process_group(p));
- attach_pid(p, PIDTYPE_SID, p->signal->session);
-
- list_add_tail(&p->tasks, &init_task.tasks);
- if (p->pid)
+ if (likely(p->pid)) {
+ add_parent(p);
+ if (unlikely(p->ptrace & PT_PTRACED))
+ __ptrace_link(p, current->parent);
+
+ if (thread_group_leader(p)) {
+ p->signal->tty = current->signal->tty;
+ p->signal->pgrp = process_group(current);
+ p->signal->session = current->signal->session;
+ attach_pid(p, PIDTYPE_PGID, process_group(p));
+ attach_pid(p, PIDTYPE_SID, p->signal->session);
+
+ 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++;
}
- attach_pid(p, PIDTYPE_TGID, p->tgid);
- attach_pid(p, PIDTYPE_PID, p->pid);
- nr_threads++;
total_forks++;
spin_unlock(&current->sighand->siglock);
write_unlock_irq(&tasklist_lock);
@@ -1263,7 +1264,7 @@ task_t * __devinit fork_idle(int cpu)
if (!task)
return ERR_PTR(-ENOMEM);
init_idle(task, cpu);
- unhash_process(task);
+
return task;
}
diff --git a/kernel/pid.c b/kernel/pid.c
index 7781d9999058..a9f2dfd006d2 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -247,16 +247,8 @@ void __init pidhash_init(void)
void __init pidmap_init(void)
{
- int i;
-
pidmap_array->page = (void *)get_zeroed_page(GFP_KERNEL);
+ /* Reserve PID 0. We never call free_pidmap(0) */
set_bit(0, pidmap_array->page);
atomic_dec(&pidmap_array->nr_free);
-
- /*
- * Allocate PID 0, and hash it via all PID types:
- */
-
- for (i = 0; i < PIDTYPE_MAX; i++)
- attach_pid(current, i, 0);
}