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Date: Mon, 19 Sep 2011 14:48:44 -0700
From: Andi Kleen <andi@...stfloor.org>
To: tglx@...utronix.de
Cc: linux-kernel@...r.kernel.org, eric.dumazet@...il.com,
akpm@...ux-foundation.org, Andi Kleen <ak@...ux.intel.com>
Subject: [PATCH 1/2] posix-timers: move global timer id management to signal_struct v4
From: Andi Kleen <ak@...ux.intel.com>
Move the global posix timer ids IDR to signal_struct. This removes
a minor global scalability bottleneck and also allows to finally limit
the number of process timers in a sane way (see next patch)
I put it into signal_struct following the other posix timer per process
structures.
v2: Now with locking again (thanks Eric)
v3: Fix the locking too (Eric Dumazet)
v4: Use a mutex. Get rid of retry loop.
idr_pre_get() is still there to avoid major surgery in lib/idr.c.
Random gleixnerfication
Signed-off-by: Andi Kleen <ak@...ux.intel.com>
---
include/linux/init_task.h | 4 ++++
include/linux/sched.h | 4 ++++
kernel/fork.c | 3 +++
kernel/posix-timers.c | 32 ++++++++++++++------------------
4 files changed, 25 insertions(+), 18 deletions(-)
diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index d14e058..d84569d 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -10,6 +10,8 @@
#include <linux/pid_namespace.h>
#include <linux/user_namespace.h>
#include <linux/securebits.h>
+#include <linux/idr.h>
+
#include <net/net_namespace.h>
#ifdef CONFIG_SMP
@@ -46,6 +48,8 @@ extern struct fs_struct init_fs;
}, \
.cred_guard_mutex = \
__MUTEX_INITIALIZER(sig.cred_guard_mutex), \
+ .posix_timers_id = IDR_INIT(posix_timer_id), \
+ .idr_lock = __MUTEX_INITIALIZER(init_signals.idr_lock), \
INIT_THREADGROUP_FORK_LOCK(sig) \
}
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 4ac2c05..2d0b39f 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -62,6 +62,7 @@ struct sched_param {
#include <linux/errno.h>
#include <linux/nodemask.h>
#include <linux/mm_types.h>
+#include <linux/idr.h>
#include <asm/system.h>
#include <asm/page.h>
@@ -652,6 +653,9 @@ struct signal_struct {
struct mutex cred_guard_mutex; /* guard against foreign influences on
* credential calculations
* (notably. ptrace) */
+
+ struct idr posix_timers_id;
+ struct mutex idr_lock; /* Protect posix_timers_id writes */
};
/* Context switch must be unlocked if interrupts are to be enabled */
diff --git a/kernel/fork.c b/kernel/fork.c
index 8e6b6f4..6693fc0 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -943,6 +943,9 @@ static void posix_cpu_timers_init_group(struct signal_struct *sig)
INIT_LIST_HEAD(&sig->cpu_timers[0]);
INIT_LIST_HEAD(&sig->cpu_timers[1]);
INIT_LIST_HEAD(&sig->cpu_timers[2]);
+
+ idr_init(&sig->posix_timers_id);
+ mutex_init(&sig->idr_lock);
}
static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
diff --git a/kernel/posix-timers.c b/kernel/posix-timers.c
index 4556182..f832021 100644
--- a/kernel/posix-timers.c
+++ b/kernel/posix-timers.c
@@ -70,8 +70,6 @@
* Lets keep our timers in a slab cache :-)
*/
static struct kmem_cache *posix_timers_cache;
-static struct idr posix_timers_id;
-static DEFINE_SPINLOCK(idr_lock);
/*
* we assume that the new SIGEV_THREAD_ID shares no bits with the other
@@ -282,7 +280,6 @@ static __init int init_posix_timers(void)
posix_timers_cache = kmem_cache_create("posix_timers_cache",
sizeof (struct k_itimer), 0, SLAB_PANIC,
NULL);
- idr_init(&posix_timers_id);
return 0;
}
@@ -503,10 +500,10 @@ static void k_itimer_rcu_free(struct rcu_head *head)
static void release_posix_timer(struct k_itimer *tmr, int it_id_set)
{
if (it_id_set) {
- unsigned long flags;
- spin_lock_irqsave(&idr_lock, flags);
- idr_remove(&posix_timers_id, tmr->it_id);
- spin_unlock_irqrestore(&idr_lock, flags);
+ struct signal_struct *s = current->signal;
+ mutex_lock(&s->idr_lock);
+ idr_remove(&s->posix_timers_id, tmr->it_id);
+ mutex_unlock(&s->idr_lock);
}
put_pid(tmr->it_pid);
sigqueue_free(tmr->sigq);
@@ -541,6 +538,7 @@ SYSCALL_DEFINE3(timer_create, const clockid_t, which_clock,
int error, new_timer_id;
sigevent_t event;
int it_id_set = IT_ID_NOT_SET;
+ struct signal_struct *sig = current->signal;
if (!kc)
return -EINVAL;
@@ -552,17 +550,13 @@ SYSCALL_DEFINE3(timer_create, const clockid_t, which_clock,
return -EAGAIN;
spin_lock_init(&new_timer->it_lock);
- retry:
- if (unlikely(!idr_pre_get(&posix_timers_id, GFP_KERNEL))) {
- error = -EAGAIN;
- goto out;
- }
- spin_lock_irq(&idr_lock);
- error = idr_get_new(&posix_timers_id, new_timer, &new_timer_id);
- spin_unlock_irq(&idr_lock);
+ mutex_lock(&sig->idr_lock);
+ error = -EAGAIN;
+ if (idr_pre_get(&sig->posix_timers_id, GFP_KERNEL))
+ error = idr_get_new(&sig->posix_timers_id, new_timer,
+ &new_timer_id);
+ mutex_unlock(&sig->idr_lock);
if (error) {
- if (error == -EAGAIN)
- goto retry;
/*
* Weird looking, but we return EAGAIN if the IDR is
* full (proper POSIX return value for this)
@@ -638,9 +632,10 @@ out:
static struct k_itimer *__lock_timer(timer_t timer_id, unsigned long *flags)
{
struct k_itimer *timr;
+ struct signal_struct *s = current->signal;
rcu_read_lock();
- timr = idr_find(&posix_timers_id, (int)timer_id);
+ timr = idr_find(&s->posix_timers_id, (int)timer_id);
if (timr) {
spin_lock_irqsave(&timr->it_lock, *flags);
if (timr->it_signal == current->signal) {
@@ -945,6 +940,7 @@ void exit_itimers(struct signal_struct *sig)
tmr = list_entry(sig->posix_timers.next, struct k_itimer, list);
itimer_delete(tmr);
}
+ idr_destroy(&sig->posix_timers_id);
}
SYSCALL_DEFINE2(clock_settime, const clockid_t, which_clock,
--
1.7.4.4
--
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