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Date: Mon, 11 Feb 2008 14:33:49 +0100
From: Peter Zijlstra <a.p.zijlstra@...llo.nl>
To: "Denis V. Lunev" <den@...ru>
Cc: Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
vatsa <vatsa@...ux.vnet.ibm.com>
Subject: Re: lock_task_group_list() can be called from the atomic context
On Mon, 2008-02-11 at 15:09 +0300, Denis V. Lunev wrote:
Curious, I hadn't yet seen it... Does the below fix it?
> BUG: sleeping function called from invalid context
> at /home/den/src/linux-netns26/kernel/mutex.c:209
> in_atomic():1, irqs_disabled():0
> no locks held by swapper/0.
> Pid: 0, comm: swapper Not tainted 2.6.24 #304
>
> Call Trace:
> <IRQ> [<ffffffff80252d1e>] ? __debug_show_held_locks+0x15/0x27
> [<ffffffff8022c2a8>] __might_sleep+0xc0/0xdf
> [<ffffffff8049f1df>] mutex_lock_nested+0x28/0x2a9
> [<ffffffff80231294>] sched_destroy_group+0x18/0xea
> [<ffffffff8023e835>] sched_destroy_user+0xd/0xf
> [<ffffffff8023e8c1>] free_uid+0x8a/0xab
> [<ffffffff80233e24>] __put_task_struct+0x3f/0xd3
> [<ffffffff80236708>] delayed_put_task_struct+0x23/0x25
> [<ffffffff8026fda7>] __rcu_process_callbacks+0x8d/0x215
> [<ffffffff8026ff52>] rcu_process_callbacks+0x23/0x44
> [<ffffffff8023a2ae>] __do_softirq+0x79/0xf8
> [<ffffffff8020f8c3>] ? profile_pc+0x2a/0x67
> [<ffffffff8020d38c>] call_softirq+0x1c/0x30
> [<ffffffff8020f689>] do_softirq+0x61/0x9c
> [<ffffffff8023a233>] irq_exit+0x51/0x53
> [<ffffffff8021bd1a>] smp_apic_timer_interrupt+0x77/0xad
> [<ffffffff8020ce3b>] apic_timer_interrupt+0x6b/0x70
> <EOI> [<ffffffff8020b0dd>] ? default_idle+0x43/0x76
> [<ffffffff8020b0db>] ? default_idle+0x41/0x76
> [<ffffffff8020b09a>] ? default_idle+0x0/0x76
> [<ffffffff8020b186>] ? cpu_idle+0x76/0x98
separate the tg->shares protection from the task_group lock.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
---
kernel/sched.c | 37 +++++++++++++++++--------------------
1 file changed, 17 insertions(+), 20 deletions(-)
Index: linux-2.6/kernel/sched.c
===================================================================
--- linux-2.6.orig/kernel/sched.c
+++ linux-2.6/kernel/sched.c
@@ -232,10 +232,10 @@ static struct cfs_rq *init_cfs_rq_p[NR_C
static struct sched_rt_entity *init_sched_rt_entity_p[NR_CPUS];
static struct rt_rq *init_rt_rq_p[NR_CPUS];
-/* task_group_mutex serializes add/remove of task groups and also changes to
+/* task_group_lock serializes add/remove of task groups and also changes to
* a task group's cpu shares.
*/
-static DEFINE_MUTEX(task_group_mutex);
+static DEFINE_SPINLOCK(task_group_lock);
/* doms_cur_mutex serializes access to doms_cur[] array */
static DEFINE_MUTEX(doms_cur_mutex);
@@ -295,16 +295,6 @@ static inline void set_task_rq(struct ta
p->rt.parent = task_group(p)->rt_se[cpu];
}
-static inline void lock_task_group_list(void)
-{
- mutex_lock(&task_group_mutex);
-}
-
-static inline void unlock_task_group_list(void)
-{
- mutex_unlock(&task_group_mutex);
-}
-
static inline void lock_doms_cur(void)
{
mutex_lock(&doms_cur_mutex);
@@ -318,8 +308,6 @@ static inline void unlock_doms_cur(void)
#else
static inline void set_task_rq(struct task_struct *p, unsigned int cpu) { }
-static inline void lock_task_group_list(void) { }
-static inline void unlock_task_group_list(void) { }
static inline void lock_doms_cur(void) { }
static inline void unlock_doms_cur(void) { }
@@ -7571,6 +7559,7 @@ struct task_group *sched_create_group(vo
struct rt_rq *rt_rq;
struct sched_rt_entity *rt_se;
struct rq *rq;
+ unsigned long flags;
int i;
tg = kzalloc(sizeof(*tg), GFP_KERNEL);
@@ -7620,7 +7609,7 @@ struct task_group *sched_create_group(vo
init_tg_rt_entry(rq, tg, rt_rq, rt_se, i, 0);
}
- lock_task_group_list();
+ spin_lock_irqsave(&task_group_lock, flags);
for_each_possible_cpu(i) {
rq = cpu_rq(i);
cfs_rq = tg->cfs_rq[i];
@@ -7629,7 +7618,7 @@ struct task_group *sched_create_group(vo
list_add_rcu(&rt_rq->leaf_rt_rq_list, &rq->leaf_rt_rq_list);
}
list_add_rcu(&tg->list, &task_groups);
- unlock_task_group_list();
+ spin_unlock_irqrestore(&task_group_lock, flags);
return tg;
@@ -7650,9 +7639,10 @@ void sched_destroy_group(struct task_gro
{
struct cfs_rq *cfs_rq = NULL;
struct rt_rq *rt_rq = NULL;
+ unsigned long flags;
int i;
- lock_task_group_list();
+ spin_lock_irqsave(&task_group_lock, flags);
for_each_possible_cpu(i) {
cfs_rq = tg->cfs_rq[i];
list_del_rcu(&cfs_rq->leaf_cfs_rq_list);
@@ -7660,7 +7650,7 @@ void sched_destroy_group(struct task_gro
list_del_rcu(&rt_rq->leaf_rt_rq_list);
}
list_del_rcu(&tg->list);
- unlock_task_group_list();
+ spin_unlock_irqrestore(&task_group_lock, flags);
BUG_ON(!cfs_rq);
@@ -7728,13 +7718,16 @@ static void set_se_shares(struct sched_e
}
}
+static DEFINE_MUTEX(shares_mutex);
+
int sched_group_set_shares(struct task_group *tg, unsigned long shares)
{
int i;
struct cfs_rq *cfs_rq;
struct rq *rq;
+ unsigned long flags;
- lock_task_group_list();
+ mutex_lock(&shares_mutex);
if (tg->shares == shares)
goto done;
@@ -7746,10 +7739,12 @@ int sched_group_set_shares(struct task_g
* load_balance_fair) from referring to this group first,
* by taking it off the rq->leaf_cfs_rq_list on each cpu.
*/
+ spin_lock_irqsave(&task_group_lock, flags);
for_each_possible_cpu(i) {
cfs_rq = tg->cfs_rq[i];
list_del_rcu(&cfs_rq->leaf_cfs_rq_list);
}
+ spin_unlock_irqrestore(&task_group_lock, flags);
/* wait for any ongoing reference to this group to finish */
synchronize_sched();
@@ -7769,13 +7764,15 @@ int sched_group_set_shares(struct task_g
* Enable load balance activity on this group, by inserting it back on
* each cpu's rq->leaf_cfs_rq_list.
*/
+ spin_lock_irqsave(&task_group_lock, flags);
for_each_possible_cpu(i) {
rq = cpu_rq(i);
cfs_rq = tg->cfs_rq[i];
list_add_rcu(&cfs_rq->leaf_cfs_rq_list, &rq->leaf_cfs_rq_list);
}
+ spin_unlock_irqrestore(&task_group_lock, flags);
done:
- unlock_task_group_list();
+ mutex_unlock(&shares_mutex);
return 0;
}
--
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