drm/i915/execlists: Track active elements during dequeue

[linux.git] / kernel / signal.c

diff --git a/kernel/signal.c b/kernel/signal.c
index 9ad8dea93dbb23482d18b24c3be220cb775f80eb..5b2396350dd183cc3ce04d115763cc590d5e3cc0 100644 (file)
--- 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);
 }