[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>

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 6735c1cf334caba982d9a8dee39a9e70c8fe50de..eafe4a7b8237d902e31eef13aaacd212ea5b84f4 100644 (file)
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -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
 };

diff --git a/include/linux/taskstats_kern.h b/include/linux/taskstats_kern.h
index 664224008fb2ec600a1a32ca7b3ea395e60a964a..6562a2050a25a6c0d5762b338d80ea8e1c81d476 100644 (file)
--- a/include/linux/taskstats_kern.h
+++ b/include/linux/taskstats_kern.h
@@ -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)
 {}

diff --git a/kernel/fork.c b/kernel/fork.c
index 213326609bac246ac91b6f4b9ed73d7ce9f7e676..3da978eec791216dd796cd704aed67b263713fa1 100644 (file)
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -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);

diff --git a/kernel/taskstats.c b/kernel/taskstats.c
index 9aeee511a46309b94795821e392ab14c88b54168..b2efda94615ac8516e67ca0b959832e3ab349218 100644 (file)
--- a/kernel/taskstats.c
+++ b/kernel/taskstats.c
@@ -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 */