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From 1f9d07b4cf227f0cf0800f96c10f9ef143b5d663 Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Fri, 3 Jul 2009 08:44:56 -0500
Subject: [PATCH 283/323] signals: Allow rt tasks to cache one sigqueue struct
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.10/older/patches-5.10.204-rt100.tar.xz
To avoid allocation allow rt tasks to cache one sigqueue struct in
task struct.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
include/linux/sched.h | 1 +
include/linux/signal.h | 1 +
kernel/exit.c | 2 +-
kernel/fork.c | 1 +
kernel/signal.c | 69 +++++++++++++++++++++++++++++++++++++++---
5 files changed, 69 insertions(+), 5 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 665a17e4f69b..a73528e8235d 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -992,6 +992,7 @@ struct task_struct {
/* Signal handlers: */
struct signal_struct *signal;
struct sighand_struct __rcu *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 b256f9c65661..ebf6c515a7b2 100644
--- a/include/linux/signal.h
+++ b/include/linux/signal.h
@@ -265,6 +265,7 @@ 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 bacdaf980933..b86f388d3e64 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -199,7 +199,7 @@ 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 2a11bf5f9e30..dfefb6e7e082 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -2046,6 +2046,7 @@ 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 e8819aabe3cd..e1f263cbcf09 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -20,6 +20,7 @@
#include <linux/sched/task.h>
#include <linux/sched/task_stack.h>
#include <linux/sched/cputime.h>
+#include <linux/sched/rt.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/proc_fs.h>
@@ -404,13 +405,30 @@ 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;
@@ -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 = get_task_cache(t);
+ if (!q)
+ q = kmem_cache_alloc(sigqueue_cachep, flags);
} else {
print_dropped_signal(sig);
}
@@ -449,6 +470,13 @@ __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)
@@ -458,6 +486,21 @@ 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;
@@ -470,6 +513,21 @@ 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.
*/
@@ -594,7 +652,7 @@ static void collect_signal(int sig, struct sigpending *list, kernel_siginfo_t *i
(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
@@ -631,6 +689,8 @@ int dequeue_signal(struct task_struct *tsk, sigset_t *mask, kernel_siginfo_t *in
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
*/
@@ -1835,7 +1895,8 @@ 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;
--
2.43.0
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