Commit b8534d7b authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds
Browse files

[PATCH] taskstats: kill ->taskstats_lock in favor of ->siglock 



signal_struct is (mostly) protected by ->sighand->siglock, I think we don't
need ->taskstats_lock to protect ->stats.  This also allows us to simplify the
locking in fill_tgid().

Signed-off-by: default avatarOleg Nesterov <oleg@tv-sign.ru>
Cc: Shailabh Nagar <nagar@watson.ibm.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Jay Lan <jlan@sgi.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 17b02695

include/linux/sched.h

+0 −1
Original line number Original line Diff line number Diff line
@@ -466,7 +466,6 @@ struct signal_struct { 
	struct pacct_struct pacct;	/* per-process accounting information */

	struct pacct_struct pacct;	/* per-process accounting information */

#endif

#endif

#ifdef CONFIG_TASKSTATS

#ifdef CONFIG_TASKSTATS

	spinlock_t stats_lock;

	struct taskstats *stats;

	struct taskstats *stats;

#endif

#endif

};

};

include/linux/taskstats_kern.h

+6 −9
Original line number Original line Diff line number Diff line
@@ -23,28 +23,26 @@ static inline void taskstats_exit_free(struct taskstats *tidstats) 




static inline void taskstats_tgid_init(struct signal_struct *sig)

static inline void taskstats_tgid_init(struct signal_struct *sig)

{

{

	spin_lock_init(&sig->stats_lock);

	sig->stats = NULL;

	sig->stats = NULL;

}

}





static inline void taskstats_tgid_alloc(struct signal_struct *sig)

static inline void taskstats_tgid_alloc(struct task_struct *tsk)

{

{

	struct signal_struct *sig = tsk->signal;

	struct taskstats *stats;

	struct taskstats *stats;

	unsigned long flags;





	if (sig->stats != NULL)

	if (sig->stats != NULL)

		return;

		return;





	/* No problem if kmem_cache_zalloc() fails */

	stats = kmem_cache_zalloc(taskstats_cache, SLAB_KERNEL);

	stats = kmem_cache_zalloc(taskstats_cache, SLAB_KERNEL);

	if (!stats)

		return;





	spin_lock_irqsave(&sig->stats_lock, flags);

	spin_lock_irq(&tsk->sighand->siglock);

	if (!sig->stats) {

	if (!sig->stats) {

		sig->stats = stats;

		sig->stats = stats;

		stats = NULL;

		stats = NULL;

	}

	}

	spin_unlock_irqrestore(&sig->stats_lock, flags);

	spin_unlock_irq(&tsk->sighand->siglock);





	if (stats)

	if (stats)

		kmem_cache_free(taskstats_cache, stats);

		kmem_cache_free(taskstats_cache, stats);
@@ -59,7 +57,6 @@ static inline void taskstats_tgid_free(struct signal_struct *sig) 
extern void taskstats_exit_alloc(struct taskstats **, unsigned int *);

extern void taskstats_exit_alloc(struct taskstats **, unsigned int *);

extern void taskstats_exit_send(struct task_struct *, struct taskstats *, int, unsigned int);

extern void taskstats_exit_send(struct task_struct *, struct taskstats *, int, unsigned int);

extern void taskstats_init_early(void);

extern void taskstats_init_early(void);

extern void taskstats_tgid_alloc(struct signal_struct *);

#else

#else

static inline void taskstats_exit_alloc(struct taskstats **ptidstats, unsigned int *mycpu)

static inline void taskstats_exit_alloc(struct taskstats **ptidstats, unsigned int *mycpu)

{}

{}
@@ -71,7 +68,7 @@ static inline void taskstats_exit_send(struct task_struct *tsk, 
{}

{}

static inline void taskstats_tgid_init(struct signal_struct *sig)

static inline void taskstats_tgid_init(struct signal_struct *sig)

{}

{}

static inline void taskstats_tgid_alloc(struct signal_struct *sig)

static inline void taskstats_tgid_alloc(struct task_struct *tsk)

{}

{}

static inline void taskstats_tgid_free(struct signal_struct *sig)

static inline void taskstats_tgid_free(struct signal_struct *sig)

{}

{}

kernel/fork.c

+1 −1
Original line number Original line Diff line number Diff line
@@ -830,7 +830,7 @@ static inline int copy_signal(unsigned long clone_flags, struct task_struct * ts 
	if (clone_flags & CLONE_THREAD) {

	if (clone_flags & CLONE_THREAD) {

		atomic_inc(&current->signal->count);

		atomic_inc(&current->signal->count);

		atomic_inc(&current->signal->live);

		atomic_inc(&current->signal->live);

		taskstats_tgid_alloc(current->signal);

		taskstats_tgid_alloc(current);

		return 0;

		return 0;

	}

	}

	sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);

	sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);

kernel/taskstats.c

+6 −10
Original line number Original line Diff line number Diff line
@@ -241,11 +241,11 @@ static int fill_tgid(pid_t tgid, struct task_struct *tgidtsk, 
	tsk = first;

	tsk = first;

	read_lock(&tasklist_lock);

	read_lock(&tasklist_lock);

	/* Start with stats from dead tasks */

	/* Start with stats from dead tasks */

	if (first->signal) {

	if (first->sighand) {

		spin_lock_irqsave(&first->signal->stats_lock, flags);

		spin_lock_irqsave(&first->sighand->siglock, flags);

		if (first->signal->stats)

		if (first->signal->stats)

			memcpy(stats, first->signal->stats, sizeof(*stats));

			memcpy(stats, first->signal->stats, sizeof(*stats));

		spin_unlock_irqrestore(&first->signal->stats_lock, flags);

		spin_unlock_irqrestore(&first->sighand->siglock, flags);

	}

	}





	do {

	do {
@@ -276,7 +276,7 @@ static void fill_tgid_exit(struct task_struct *tsk) 
{

{

	unsigned long flags;

	unsigned long flags;





	spin_lock_irqsave(&tsk->signal->stats_lock, flags);

	spin_lock_irqsave(&tsk->sighand->siglock, flags);

	if (!tsk->signal->stats)

	if (!tsk->signal->stats)

		goto ret;

		goto ret;
@@ -288,7 +288,7 @@ static void fill_tgid_exit(struct task_struct *tsk) 
	 */

	 */

	delayacct_add_tsk(tsk->signal->stats, tsk);

	delayacct_add_tsk(tsk->signal->stats, tsk);

ret:

ret:

	spin_unlock_irqrestore(&tsk->signal->stats_lock, flags);

	spin_unlock_irqrestore(&tsk->sighand->siglock, flags);

	return;

	return;

}

}
@@ -464,15 +464,10 @@ void taskstats_exit_send(struct task_struct *tsk, struct taskstats *tidstats, 
	size_t size;

	size_t size;

	int is_thread_group;

	int is_thread_group;

	struct nlattr *na;

	struct nlattr *na;

	unsigned long flags;





	if (!family_registered || !tidstats)

	if (!family_registered || !tidstats)

		return;

		return;





	spin_lock_irqsave(&tsk->signal->stats_lock, flags);

	is_thread_group = tsk->signal->stats ? 1 : 0;

	spin_unlock_irqrestore(&tsk->signal->stats_lock, flags);



	rc = 0;

	rc = 0;

	/*

	/*

	 * Size includes space for nested attributes

	 * Size includes space for nested attributes
@@ -480,6 +475,7 @@ void taskstats_exit_send(struct task_struct *tsk, struct taskstats *tidstats, 
	size = nla_total_size(sizeof(u32)) +

	size = nla_total_size(sizeof(u32)) +

		nla_total_size(sizeof(struct taskstats)) + nla_total_size(0);

		nla_total_size(sizeof(struct taskstats)) + nla_total_size(0);





	is_thread_group = (tsk->signal->stats != NULL);

	if (is_thread_group)

	if (is_thread_group)

		size = 2 * size;	/* PID + STATS + TGID + STATS */

		size = 2 * size;	/* PID + STATS + TGID + STATS */