[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>

2 files changed, 6 insertions, 10 deletions

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 6735c1cf334c..eafe4a7b8237 100644
--- 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 664224008fb2..6562a2050a25 100644
--- 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)
 {}