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-rw-r--r--kernel/signal.c23
1 files changed, 14 insertions, 9 deletions
diff --git a/kernel/signal.c b/kernel/signal.c
index 9ad8dea93dbb..5b2396350dd1 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -413,27 +413,32 @@ __sigqueue_alloc(int sig, struct task_struct *t, gfp_t flags, int override_rlimi
{
struct sigqueue *q = NULL;
struct user_struct *user;
+ int sigpending;
/*
* Protect access to @t credentials. This can go away when all
* callers hold rcu read lock.
+ *
+ * NOTE! A pending signal will hold on to the user refcount,
+ * and we get/put the refcount only when the sigpending count
+ * changes from/to zero.
*/
rcu_read_lock();
- user = get_uid(__task_cred(t)->user);
- atomic_inc(&user->sigpending);
+ user = __task_cred(t)->user;
+ sigpending = atomic_inc_return(&user->sigpending);
+ if (sigpending == 1)
+ get_uid(user);
rcu_read_unlock();
- if (override_rlimit ||
- atomic_read(&user->sigpending) <=
- task_rlimit(t, RLIMIT_SIGPENDING)) {
+ if (override_rlimit || likely(sigpending <= task_rlimit(t, RLIMIT_SIGPENDING))) {
q = kmem_cache_alloc(sigqueue_cachep, flags);
} else {
print_dropped_signal(sig);
}
if (unlikely(q == NULL)) {
- atomic_dec(&user->sigpending);
- free_uid(user);
+ if (atomic_dec_and_test(&user->sigpending))
+ free_uid(user);
} else {
INIT_LIST_HEAD(&q->list);
q->flags = 0;
@@ -447,8 +452,8 @@ static void __sigqueue_free(struct sigqueue *q)
{
if (q->flags & SIGQUEUE_PREALLOC)
return;
- atomic_dec(&q->user->sigpending);
- free_uid(q->user);
+ if (atomic_dec_and_test(&q->user->sigpending))
+ free_uid(q->user);
kmem_cache_free(sigqueue_cachep, q);
}