201 lines
5.1 KiB
Diff
201 lines
5.1 KiB
Diff
From e35585fe22932e9eb9cf60dc1080b05935cc99ce Mon Sep 17 00:00:00 2001
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From: Thomas Gleixner <tglx@linutronix.de>
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Date: Fri, 3 Jul 2009 08:44:56 -0500
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Subject: [PATCH 261/328] signals: Allow rt tasks to cache one sigqueue struct
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.106-rt46.tar.xz
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To avoid allocation allow rt tasks to cache one sigqueue struct in
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task struct.
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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---
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include/linux/sched.h | 2 ++
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include/linux/signal.h | 1 +
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kernel/exit.c | 2 +-
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kernel/fork.c | 1 +
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kernel/signal.c | 69 +++++++++++++++++++++++++++++++++++++++---
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5 files changed, 70 insertions(+), 5 deletions(-)
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--- a/include/linux/sched.h
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+++ b/include/linux/sched.h
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@@ -895,6 +895,8 @@
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/* Signal handlers: */
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struct signal_struct *signal;
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struct sighand_struct *sighand;
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+ struct sigqueue *sigqueue_cache;
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+
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sigset_t blocked;
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sigset_t real_blocked;
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/* Restored if set_restore_sigmask() was used: */
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--- a/include/linux/signal.h
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+++ b/include/linux/signal.h
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@@ -245,6 +245,7 @@
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}
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extern void flush_sigqueue(struct sigpending *queue);
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+extern void flush_task_sigqueue(struct task_struct *tsk);
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/* Test if 'sig' is valid signal. Use this instead of testing _NSIG directly */
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static inline int valid_signal(unsigned long sig)
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--- a/kernel/exit.c
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+++ b/kernel/exit.c
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@@ -160,7 +160,7 @@
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* Do this under ->siglock, we can race with another thread
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* doing sigqueue_free() if we have SIGQUEUE_PREALLOC signals.
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*/
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- flush_sigqueue(&tsk->pending);
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+ flush_task_sigqueue(tsk);
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tsk->sighand = NULL;
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spin_unlock(&sighand->siglock);
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--- a/kernel/fork.c
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+++ b/kernel/fork.c
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@@ -1842,6 +1842,7 @@
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spin_lock_init(&p->alloc_lock);
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init_sigpending(&p->pending);
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+ p->sigqueue_cache = NULL;
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p->utime = p->stime = p->gtime = 0;
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#ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
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--- a/kernel/signal.c
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+++ b/kernel/signal.c
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@@ -19,6 +19,7 @@
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#include <linux/sched/task.h>
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#include <linux/sched/task_stack.h>
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#include <linux/sched/cputime.h>
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+#include <linux/sched/rt.h>
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#include <linux/fs.h>
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#include <linux/tty.h>
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#include <linux/binfmts.h>
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@@ -397,13 +398,30 @@
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}
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}
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+static inline struct sigqueue *get_task_cache(struct task_struct *t)
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+{
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+ struct sigqueue *q = t->sigqueue_cache;
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+
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+ if (cmpxchg(&t->sigqueue_cache, q, NULL) != q)
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+ return NULL;
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+ return q;
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+}
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+
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+static inline int put_task_cache(struct task_struct *t, struct sigqueue *q)
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+{
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+ if (cmpxchg(&t->sigqueue_cache, NULL, q) == NULL)
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+ return 0;
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+ return 1;
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+}
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+
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/*
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* allocate a new signal queue record
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* - this may be called without locks if and only if t == current, otherwise an
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* appropriate lock must be held to stop the target task from exiting
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*/
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static struct sigqueue *
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-__sigqueue_alloc(int sig, struct task_struct *t, gfp_t flags, int override_rlimit)
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+__sigqueue_do_alloc(int sig, struct task_struct *t, gfp_t flags,
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+ int override_rlimit, int fromslab)
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{
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struct sigqueue *q = NULL;
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struct user_struct *user;
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@@ -425,7 +443,10 @@
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rcu_read_unlock();
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if (override_rlimit || likely(sigpending <= task_rlimit(t, RLIMIT_SIGPENDING))) {
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- q = kmem_cache_alloc(sigqueue_cachep, flags);
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+ if (!fromslab)
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+ q = get_task_cache(t);
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+ if (!q)
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+ q = kmem_cache_alloc(sigqueue_cachep, flags);
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} else {
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print_dropped_signal(sig);
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}
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@@ -442,6 +463,13 @@
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return q;
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}
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+static struct sigqueue *
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+__sigqueue_alloc(int sig, struct task_struct *t, gfp_t flags,
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+ int override_rlimit)
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+{
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+ return __sigqueue_do_alloc(sig, t, flags, override_rlimit, 0);
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+}
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+
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static void __sigqueue_free(struct sigqueue *q)
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{
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if (q->flags & SIGQUEUE_PREALLOC)
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@@ -451,6 +479,21 @@
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kmem_cache_free(sigqueue_cachep, q);
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}
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+static void sigqueue_free_current(struct sigqueue *q)
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+{
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+ struct user_struct *up;
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+
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+ if (q->flags & SIGQUEUE_PREALLOC)
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+ return;
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+
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+ up = q->user;
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+ if (rt_prio(current->normal_prio) && !put_task_cache(current, q)) {
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+ atomic_dec(&up->sigpending);
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+ free_uid(up);
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+ } else
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+ __sigqueue_free(q);
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+}
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+
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void flush_sigqueue(struct sigpending *queue)
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{
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struct sigqueue *q;
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@@ -464,6 +507,21 @@
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}
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/*
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+ * Called from __exit_signal. Flush tsk->pending and
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+ * tsk->sigqueue_cache
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+ */
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+void flush_task_sigqueue(struct task_struct *tsk)
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+{
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+ struct sigqueue *q;
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+
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+ flush_sigqueue(&tsk->pending);
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+
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+ q = get_task_cache(tsk);
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+ if (q)
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+ kmem_cache_free(sigqueue_cachep, q);
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+}
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+
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+/*
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* Flush all pending signals for this kthread.
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*/
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void flush_signals(struct task_struct *t)
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@@ -586,7 +644,7 @@
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(info->si_code == SI_TIMER) &&
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(info->si_sys_private);
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- __sigqueue_free(first);
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+ sigqueue_free_current(first);
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} else {
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/*
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* Ok, it wasn't in the queue. This must be
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@@ -623,6 +681,8 @@
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bool resched_timer = false;
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int signr;
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+ WARN_ON_ONCE(tsk != current);
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+
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/* We only dequeue private signals from ourselves, we don't let
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* signalfd steal them
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*/
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@@ -1762,7 +1822,8 @@
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*/
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struct sigqueue *sigqueue_alloc(void)
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{
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- struct sigqueue *q = __sigqueue_alloc(-1, current, GFP_KERNEL, 0);
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+ /* Preallocated sigqueue objects always from the slabcache ! */
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+ struct sigqueue *q = __sigqueue_do_alloc(-1, current, GFP_KERNEL, 0, 1);
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if (q)
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q->flags |= SIGQUEUE_PREALLOC;
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