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().
Unified · Split
| @@ -466,7 +466,6 @@ struct signal_struct { · 465 unmodified lines | ||
| 466 | 466 | struct pacct_struct pacct; /* per-process accounting information */ |
| 467 | 467 | #endif |
| 468 | 468 | #ifdef CONFIG_TASKSTATS |
| 469 | − spinlock_t stats_lock; | |
| 470 | 469 | struct taskstats *stats; |
| 471 | 470 | #endif |
| 472 | 471 | }; |
| @@ -23,28 +23,26 @@ static inline void taskstats_exit_free(struct taskstats *tidstats) · 22 unmodified lines | ||
| 23 | 23 | |
| 24 | 24 | static inline void taskstats_tgid_init(struct signal_struct *sig) |
| 25 | 25 | { |
| 26 | − spin_lock_init(&sig->stats_lock); | |
| 27 | 26 | sig->stats = NULL; |
| 28 | 27 | } |
| 29 | 28 | |
| 30 | −static inline void taskstats_tgid_alloc(struct signal_struct *sig) | |
| 29 | +static inline void taskstats_tgid_alloc(struct task_struct *tsk) | |
| 31 | 30 | { |
| 31 | + struct signal_struct *sig = tsk->signal; | |
| 32 | 32 | struct taskstats *stats; |
| 33 | − unsigned long flags; | |
| 34 | 33 | |
| 35 | 34 | if (sig->stats != NULL) |
| 36 | 35 | return; |
| 37 | 36 | |
| 37 | + /* No problem if kmem_cache_zalloc() fails */ | |
| 38 | 38 | stats = kmem_cache_zalloc(taskstats_cache, SLAB_KERNEL); |
| 39 | − if (!stats) | |
| 40 | − return; | |
| 41 | 39 | |
| 42 | − spin_lock_irqsave(&sig->stats_lock, flags); | |
| 40 | + spin_lock_irq(&tsk->sighand->siglock); | |
| 43 | 41 | if (!sig->stats) { |
| 44 | 42 | sig->stats = stats; |
| 45 | 43 | stats = NULL; |
| 46 | 44 | } |
| 47 | − spin_unlock_irqrestore(&sig->stats_lock, flags); | |
| 45 | + spin_unlock_irq(&tsk->sighand->siglock); | |
| 48 | 46 | |
| 49 | 47 | if (stats) |
| 50 | 48 | kmem_cache_free(taskstats_cache, stats); |
| @@ -59,7 +57,6 @@ static inline void taskstats_tgid_free(struct signal_struct *sig) · 8 unmodified lines | ||
| 59 | 57 | extern void taskstats_exit_alloc(struct taskstats **, unsigned int *); |
| 60 | 58 | extern void taskstats_exit_send(struct task_struct *, struct taskstats *, int, unsigned int); |
| 61 | 59 | extern void taskstats_init_early(void); |
| 62 | −extern void taskstats_tgid_alloc(struct signal_struct *); | |
| 63 | 60 | #else |
| 64 | 61 | static inline void taskstats_exit_alloc(struct taskstats **ptidstats, unsigned int *mycpu) |
| 65 | 62 | {} |
| @@ -71,7 +68,7 @@ static inline void taskstats_exit_send(struct task_struct *tsk, · 5 unmodified lines | ||
| 71 | 68 | {} |
| 72 | 69 | static inline void taskstats_tgid_init(struct signal_struct *sig) |
| 73 | 70 | {} |
| 74 | −static inline void taskstats_tgid_alloc(struct signal_struct *sig) | |
| 71 | +static inline void taskstats_tgid_alloc(struct task_struct *tsk) | |
| 75 | 72 | {} |
| 76 | 73 | static inline void taskstats_tgid_free(struct signal_struct *sig) |
| 77 | 74 | {} |
| @@ -830,7 +830,7 @@ static inline int copy_signal(unsigned long clone_flags, struct task_struct * ts · 829 unmodified lines | ||
| 830 | 830 | if (clone_flags & CLONE_THREAD) { |
| 831 | 831 | atomic_inc(¤t->signal->count); |
| 832 | 832 | atomic_inc(¤t->signal->live); |
| 833 | − taskstats_tgid_alloc(current->signal); | |
| 833 | + taskstats_tgid_alloc(current); | |
| 834 | 834 | return 0; |
| 835 | 835 | } |
| 836 | 836 | sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL); |
| @@ -241,11 +241,11 @@ static int fill_tgid(pid_t tgid, struct task_struct *tgidtsk, · 240 unmodified lines | ||
| 241 | 241 | tsk = first; |
| 242 | 242 | read_lock(&tasklist_lock); |
| 243 | 243 | /* Start with stats from dead tasks */ |
| 244 | − if (first->signal) { | |
| 245 | − spin_lock_irqsave(&first->signal->stats_lock, flags); | |
| 244 | + if (first->sighand) { | |
| 245 | + spin_lock_irqsave(&first->sighand->siglock, flags); | |
| 246 | 246 | if (first->signal->stats) |
| 247 | 247 | memcpy(stats, first->signal->stats, sizeof(*stats)); |
| 248 | − spin_unlock_irqrestore(&first->signal->stats_lock, flags); | |
| 248 | + spin_unlock_irqrestore(&first->sighand->siglock, flags); | |
| 249 | 249 | } |
| 250 | 250 | |
| 251 | 251 | do { |
| @@ -276,7 +276,7 @@ static void fill_tgid_exit(struct task_struct *tsk) · 24 unmodified lines | ||
| 276 | 276 | { |
| 277 | 277 | unsigned long flags; |
| 278 | 278 | |
| 279 | − spin_lock_irqsave(&tsk->signal->stats_lock, flags); | |
| 279 | + spin_lock_irqsave(&tsk->sighand->siglock, flags); | |
| 280 | 280 | if (!tsk->signal->stats) |
| 281 | 281 | goto ret; |
| 282 | 282 | |
| @@ -288,7 +288,7 @@ static void fill_tgid_exit(struct task_struct *tsk) · 5 unmodified lines | ||
| 288 | 288 | */ |
| 289 | 289 | delayacct_add_tsk(tsk->signal->stats, tsk); |
| 290 | 290 | ret: |
| 291 | − spin_unlock_irqrestore(&tsk->signal->stats_lock, flags); | |
| 291 | + spin_unlock_irqrestore(&tsk->sighand->siglock, flags); | |
| 292 | 292 | return; |
| 293 | 293 | } |
| 294 | 294 | |
| @@ -464,15 +464,10 @@ void taskstats_exit_send(struct task_struct *tsk, struct taskstats *tidstats, · 169 unmodified lines | ||
| 464 | 464 | size_t size; |
| 465 | 465 | int is_thread_group; |
| 466 | 466 | struct nlattr *na; |
| 467 | − unsigned long flags; | |
| 468 | 467 | |
| 469 | 468 | if (!family_registered || !tidstats) |
| 470 | 469 | return; |
| 471 | 470 | |
| 472 | − spin_lock_irqsave(&tsk->signal->stats_lock, flags); | |
| 473 | − is_thread_group = tsk->signal->stats ? 1 : 0; | |
| 474 | − spin_unlock_irqrestore(&tsk->signal->stats_lock, flags); | |
| 475 | − | |
| 476 | 471 | rc = 0; |
| 477 | 472 | /* |
| 478 | 473 | * Size includes space for nested attributes |
| @@ -480,6 +475,7 @@ void taskstats_exit_send(struct task_struct *tsk, struct taskstats *tidstats, · 1 unmodified line | ||
| 480 | 475 | size = nla_total_size(sizeof(u32)) + |
| 481 | 476 | nla_total_size(sizeof(struct taskstats)) + nla_total_size(0); |
| 482 | 477 | |
| 478 | + is_thread_group = (tsk->signal->stats != NULL); | |
| 483 | 479 | if (is_thread_group) |
| 484 | 480 | size = 2 * size; /* PID + STATS + TGID + STATS */ |
| 485 | 481 | |