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Commit b3ac022cb9dc5883505a88b159d1b240ad1ef405

Authored by Oleg Nesterov
Committed by Linus Torvalds
1 parent dd98acf747
Exists in master and in 7 other branches imx_3.0.35_4.1.0, imx_3.10.17_1.0.1_ga, imx_3.10.53_1.1.0_ga, imx_3.14.28_1.0.0_ga, smarc-imx_3.10.53_1.1.0_ga, smarc-imx_3.14.28_1.0.0_ga, smarc-l5.0.0_1.0.0-ga

proc: turn signal_struct->count into "int nr_threads" 

No functional changes, just s/atomic_t count/int nr_threads/.

With the recent changes this counter has a single user, get_nr_threads()
And, none of its callers need the really accurate number of threads, not
to mention each caller obviously races with fork/exit.  It is only used to
report this value to the user-space, except first_tid() uses it to avoid
the unnecessary while_each_thread() loop in the unlikely case.

It is a bit sad we need a word in struct signal_struct for this, perhaps
we can change get_nr_threads() to approximate the number of threads using
signal->live and kill ->nr_threads later.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Showing 4 changed files with 8 additions and 11 deletions Side-by-side Diff

include/linux/init_task.h
Diff comments   View file @ b3ac022
... ... @@ -16,7 +16,7 @@
16 16 extern struct fs_struct init_fs;
17 17  
18 18 #define INIT_SIGNALS(sig) { \
19   - .count = ATOMIC_INIT(1), \
  19 + .nr_threads = 1, \
20 20 .wait_chldexit = __WAIT_QUEUE_HEAD_INITIALIZER(sig.wait_chldexit),\
21 21 .shared_pending = { \
22 22 .list = LIST_HEAD_INIT(sig.shared_pending.list), \
include/linux/sched.h
Diff comments   View file @ b3ac022
... ... @@ -527,8 +527,8 @@
527 527 */
528 528 struct signal_struct {
529 529 atomic_t sigcnt;
530   - atomic_t count;
531 530 atomic_t live;
  531 + int nr_threads;
532 532  
533 533 wait_queue_head_t wait_chldexit; /* for wait4() */
534 534  
... ... @@ -2149,7 +2149,7 @@
2149 2149  
2150 2150 static inline int get_nr_threads(struct task_struct *tsk)
2151 2151 {
2152   - return atomic_read(&tsk->signal->count);
  2152 + return tsk->signal->nr_threads;
2153 2153 }
2154 2154  
2155 2155 /* de_thread depends on thread_group_leader not being a pid based check */
... ... @@ -83,14 +83,10 @@
83 83 struct sighand_struct *sighand;
84 84 struct tty_struct *uninitialized_var(tty);
85 85  
86   - BUG_ON(!sig);
87   - BUG_ON(!atomic_read(&sig->count));
88   -
89 86 sighand = rcu_dereference_check(tsk->sighand,
90 87 rcu_read_lock_held() ||
91 88 lockdep_tasklist_lock_is_held());
92 89 spin_lock(&sighand->siglock);
93   - atomic_dec(&sig->count);
94 90  
95 91 posix_cpu_timers_exit(tsk);
96 92 if (group_dead) {
... ... @@ -130,6 +126,7 @@
130 126 sig->sum_sched_runtime += tsk->se.sum_exec_runtime;
131 127 }
132 128  
  129 + sig->nr_threads--;
133 130 __unhash_process(tsk, group_dead);
134 131  
135 132 /*
... ... @@ -877,9 +877,9 @@
877 877 if (!sig)
878 878 return -ENOMEM;
879 879  
880   - atomic_set(&sig->sigcnt, 1);
881   - atomic_set(&sig->count, 1);
  880 + sig->nr_threads = 1;
882 881 atomic_set(&sig->live, 1);
  882 + atomic_set(&sig->sigcnt, 1);
883 883 init_waitqueue_head(&sig->wait_chldexit);
884 884 if (clone_flags & CLONE_NEWPID)
885 885 sig->flags |= SIGNAL_UNKILLABLE;
886 886  
... ... @@ -1256,9 +1256,9 @@
1256 1256 }
1257 1257  
1258 1258 if (clone_flags & CLONE_THREAD) {
1259   - atomic_inc(&current->signal->sigcnt);
1260   - atomic_inc(&current->signal->count);
  1259 + current->signal->nr_threads++;
1261 1260 atomic_inc(&current->signal->live);
  1261 + atomic_inc(&current->signal->sigcnt);
1262 1262 p->group_leader = current->group_leader;
1263 1263 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1264 1264 }