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

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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 */ 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
}; };

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) 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)
{} {}

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) { 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);

16
kernel/taskstats.c
View file

@ -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 */