From: Thomas Gleixner Date: Fri, 3 Jul 2009 08:44:56 -0500 Subject: [PATCH 258/342] signals: Allow rt tasks to cache one sigqueue struct Origin: https://git.kernel.org/cgit/linux/kernel/git/rt/linux-stable-rt.git/commit?id=5aac397e1ae3068a8bef5c75bbfbdb268c95b2c5 To avoid allocation allow rt tasks to cache one sigqueue struct in task struct. Signed-off-by: Thomas Gleixner --- include/linux/sched.h | 2 ++ include/linux/signal.h | 1 + kernel/exit.c | 2 +- kernel/fork.c | 1 + kernel/signal.c | 69 +++++++++++++++++++++++++++++++++++++++--- 5 files changed, 70 insertions(+), 5 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index 044bebd3d16f..e567fe2d7058 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -895,6 +895,8 @@ struct task_struct { /* Signal handlers: */ struct signal_struct *signal; struct sighand_struct *sighand; + struct sigqueue *sigqueue_cache; + sigset_t blocked; sigset_t real_blocked; /* Restored if set_restore_sigmask() was used: */ diff --git a/include/linux/signal.h b/include/linux/signal.h index 0be5ce2375cb..6495fda18c2c 100644 --- a/include/linux/signal.h +++ b/include/linux/signal.h @@ -245,6 +245,7 @@ static inline void init_sigpending(struct sigpending *sig) } extern void flush_sigqueue(struct sigpending *queue); +extern void flush_task_sigqueue(struct task_struct *tsk); /* Test if 'sig' is valid signal. Use this instead of testing _NSIG directly */ static inline int valid_signal(unsigned long sig) diff --git a/kernel/exit.c b/kernel/exit.c index 908e7a33e1fc..2a414fc71b87 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -160,7 +160,7 @@ static void __exit_signal(struct task_struct *tsk) * Do this under ->siglock, we can race with another thread * doing sigqueue_free() if we have SIGQUEUE_PREALLOC signals. */ - flush_sigqueue(&tsk->pending); + flush_task_sigqueue(tsk); tsk->sighand = NULL; spin_unlock(&sighand->siglock); diff --git a/kernel/fork.c b/kernel/fork.c index 51ec12803c0b..fdc61ac6a748 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1848,6 +1848,7 @@ static __latent_entropy struct task_struct *copy_process( spin_lock_init(&p->alloc_lock); init_sigpending(&p->pending); + p->sigqueue_cache = NULL; p->utime = p->stime = p->gtime = 0; #ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME diff --git a/kernel/signal.c b/kernel/signal.c index 708ee1bd4059..730ac7ff4637 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -19,6 +19,7 @@ #include #include #include +#include #include #include #include @@ -398,13 +399,30 @@ void task_join_group_stop(struct task_struct *task) task_set_jobctl_pending(task, mask | JOBCTL_STOP_PENDING); } +static inline struct sigqueue *get_task_cache(struct task_struct *t) +{ + struct sigqueue *q = t->sigqueue_cache; + + if (cmpxchg(&t->sigqueue_cache, q, NULL) != q) + return NULL; + return q; +} + +static inline int put_task_cache(struct task_struct *t, struct sigqueue *q) +{ + if (cmpxchg(&t->sigqueue_cache, NULL, q) == NULL) + return 0; + return 1; +} + /* * allocate a new signal queue record * - this may be called without locks if and only if t == current, otherwise an * appropriate lock must be held to stop the target task from exiting */ 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, int fromslab) { struct sigqueue *q = NULL; struct user_struct *user; @@ -426,7 +444,10 @@ __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 = get_task_cache(t); + if (!q) + q = kmem_cache_alloc(sigqueue_cachep, flags); } else { print_dropped_signal(sig); } @@ -443,6 +464,13 @@ __sigqueue_alloc(int sig, struct task_struct *t, gfp_t flags, int override_rlimi return q; } +static struct sigqueue * +__sigqueue_alloc(int sig, struct task_struct *t, gfp_t flags, + int override_rlimit) +{ + return __sigqueue_do_alloc(sig, t, flags, override_rlimit, 0); +} + static void __sigqueue_free(struct sigqueue *q) { if (q->flags & SIGQUEUE_PREALLOC) @@ -452,6 +480,21 @@ static void __sigqueue_free(struct sigqueue *q) kmem_cache_free(sigqueue_cachep, q); } +static void sigqueue_free_current(struct sigqueue *q) +{ + struct user_struct *up; + + if (q->flags & SIGQUEUE_PREALLOC) + return; + + up = q->user; + if (rt_prio(current->normal_prio) && !put_task_cache(current, q)) { + atomic_dec(&up->sigpending); + free_uid(up); + } else + __sigqueue_free(q); +} + void flush_sigqueue(struct sigpending *queue) { struct sigqueue *q; @@ -464,6 +507,21 @@ void flush_sigqueue(struct sigpending *queue) } } +/* + * Called from __exit_signal. Flush tsk->pending and + * tsk->sigqueue_cache + */ +void flush_task_sigqueue(struct task_struct *tsk) +{ + struct sigqueue *q; + + flush_sigqueue(&tsk->pending); + + q = get_task_cache(tsk); + if (q) + kmem_cache_free(sigqueue_cachep, q); +} + /* * Flush all pending signals for this kthread. */ @@ -587,7 +645,7 @@ static void collect_signal(int sig, struct sigpending *list, siginfo_t *info, (info->si_code == SI_TIMER) && (info->si_sys_private); - __sigqueue_free(first); + sigqueue_free_current(first); } else { /* * Ok, it wasn't in the queue. This must be @@ -624,6 +682,8 @@ int dequeue_signal(struct task_struct *tsk, sigset_t *mask, siginfo_t *info) bool resched_timer = false; int signr; + WARN_ON_ONCE(tsk != current); + /* We only dequeue private signals from ourselves, we don't let * signalfd steal them */ @@ -1762,7 +1822,8 @@ EXPORT_SYMBOL(kill_pid); */ struct sigqueue *sigqueue_alloc(void) { - struct sigqueue *q = __sigqueue_alloc(-1, current, GFP_KERNEL, 0); + /* Preallocated sigqueue objects always from the slabcache ! */ + struct sigqueue *q = __sigqueue_do_alloc(-1, current, GFP_KERNEL, 0, 1); if (q) q->flags |= SIGQUEUE_PREALLOC;