On 03/03, Sebastian Andrzej Siewior wrote:
>
> +static struct sigqueue *sigqueue_from_cache(struct task_struct *t)
> +{
> + struct sigqueue *q = t->sigqueue_cache;
> +
> + if (q && cmpxchg(&t->sigqueue_cache, q, NULL) == q)
> + return q;
> + return NULL;
> +}
> +
> +static bool sigqueue_add_cache(struct task_struct *t, struct sigqueue *q)
> +{
> + if (!t->sigqueue_cache && cmpxchg(&t->sigqueue_cache, NULL, q) == NULL)
> + return true;
> + return false;
> +}
Do we really need cmpxchg? It seems they are always called with spinlock held.
> static struct sigqueue *
> -__sigqueue_alloc(int sig, struct task_struct *t, gfp_t flags, int
> override_rlimit)
> +__sigqueue_do_alloc(int sig, struct task_struct *t, gfp_t flags,
> + int override_rlimit, bool fromslab)
> {
> struct sigqueue *q = NULL;
> struct user_struct *user;
> @@ -432,7 +450,10 @@ __sigqueue_alloc(int sig, struct task_struct *t, gfp_t
> flags, int override_rlimi
> rcu_read_unlock();
>
> if (override_rlimit || likely(sigpending <= task_rlimit(t,
> RLIMIT_SIGPENDING))) {
> - q = kmem_cache_alloc(sigqueue_cachep, flags);
> + if (!fromslab)
> + q = sigqueue_from_cache(t);
> + if (!q)
> + q = kmem_cache_alloc(sigqueue_cachep, flags);
I won't insist but afaics you can avoid the new arg/function and simplify this
patch. __sigqueue_alloc() can simply check "sig > 0" or valid_signal(sig) rather
than "!fromslab".
> +static void __sigqueue_cache_or_free(struct sigqueue *q)
> +{
> + struct user_struct *up;
> +
> + if (q->flags & SIGQUEUE_PREALLOC)
> + return;
> +
> + up = q->user;
> + if (atomic_dec_and_test(&up->sigpending))
> + free_uid(up);
> + if (!task_is_realtime(current) || !sigqueue_add_cache(current, q))
> + kmem_cache_free(sigqueue_cachep, q);
> +}
Well, this duplicates __sigqueue_free... Do we really need the new helper?
What if we simply change __sigqueue_free() to do sigqueue_add_cache() if
task_is_realtime() && !PF_EXITING ? This too can simplify the patch...
Oleg.
