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[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: Oleg 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: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Oleg Nesterov 2006-10-28 10:38:53 -07:00 committed by Linus Torvalds
parent 17b02695b2
commit b8534d7bd8
4 changed files with 13 additions and 21 deletions
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1
include/linux/sched.h
View File

@ -466,7 +466,6 @@ struct signal_struct {
struct pacct_struct pacct; /* per-process accounting information */
#endif
#ifdef CONFIG_TASKSTATS
spinlock_t stats_lock;
struct taskstats *stats;
#endif
};

15
include/linux/taskstats_kern.h
View File

@ -23,28 +23,26 @@ static inline void taskstats_exit_free(struct taskstats *tidstats)
static inline void taskstats_tgid_init(struct signal_struct *sig)
{
spin_lock_init(&sig->stats_lock);
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;
unsigned long flags;
if (sig->stats != NULL)
return;
/* No problem if kmem_cache_zalloc() fails */
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) {
sig->stats = stats;
stats = NULL;
}
spin_unlock_irqrestore(&sig->stats_lock, flags);
spin_unlock_irq(&tsk->sighand->siglock);
if (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_send(struct task_struct *, struct taskstats *, int, unsigned int);
extern void taskstats_init_early(void);
extern void taskstats_tgid_alloc(struct signal_struct *);
#else
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_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)
{}

2
kernel/fork.c
View File

@ -830,7 +830,7 @@ static inline int copy_signal(unsigned long clone_flags, struct task_struct * ts
if (clone_flags & CLONE_THREAD) {
atomic_inc(&current->signal->count);
atomic_inc(&current->signal->live);
taskstats_tgid_alloc(current->signal);
taskstats_tgid_alloc(current);
return 0;
}
sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);

16
kernel/taskstats.c
View File

@ -241,11 +241,11 @@ static int fill_tgid(pid_t tgid, struct task_struct *tgidtsk,
tsk = first;
read_lock(&tasklist_lock);
/* Start with stats from dead tasks */
if (first->signal) {
spin_lock_irqsave(&first->signal->stats_lock, flags);
if (first->sighand) {
spin_lock_irqsave(&first->sighand->siglock, flags);
if (first->signal->stats)
memcpy(stats, first->signal->stats, sizeof(*stats));
spin_unlock_irqrestore(&first->signal->stats_lock, flags);
spin_unlock_irqrestore(&first->sighand->siglock, flags);
}
do {
@ -276,7 +276,7 @@ static void fill_tgid_exit(struct task_struct *tsk)
{
unsigned long flags;
spin_lock_irqsave(&tsk->signal->stats_lock, flags);
spin_lock_irqsave(&tsk->sighand->siglock, flags);
if (!tsk->signal->stats)
goto ret;
@ -288,7 +288,7 @@ static void fill_tgid_exit(struct task_struct *tsk)
*/
delayacct_add_tsk(tsk->signal->stats, tsk);
ret:
spin_unlock_irqrestore(&tsk->signal->stats_lock, flags);
spin_unlock_irqrestore(&tsk->sighand->siglock, flags);
return;
}
@ -464,15 +464,10 @@ void taskstats_exit_send(struct task_struct *tsk, struct taskstats *tidstats,
size_t size;
int is_thread_group;
struct nlattr *na;
unsigned long flags;
if (!family_registered || !tidstats)
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;
/*
* 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)) +
nla_total_size(sizeof(struct taskstats)) + nla_total_size(0);
is_thread_group = (tsk->signal->stats != NULL);
if (is_thread_group)
size = 2 * size; /* PID + STATS + TGID + STATS */