--- /dev/null
+/*
+ * Copyright (C) 2012 Pierre Habouzit <pierre.habouzit@intersec.com>
+ * Copyright (C) 2012 Intersec SAS
+ *
+ * This file implements the Linux Pthread Workqueue Regulator, and is part
+ * of the linux kernel.
+ *
+ * The Linux Kernel is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published by
+ * the Free Software Foundation.
+ *
+ * The Linux Kernel is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
+ * License for more details.
+ *
+ * You should have received a copy of the GNU General Public License version 2
+ * along with The Linux Kernel. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/cdev.h>
+#include <linux/device.h>
+#include <linux/file.h>
+#include <linux/fs.h>
+#include <linux/hash.h>
+#include <linux/init.h>
+#include <linux/kref.h>
+#include <linux/module.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/uaccess.h>
+#include <linux/wait.h>
+
+#ifndef CONFIG_PREEMPT_NOTIFIERS
+# error PWQ module requires CONFIG_PREEMPT_NOTIFIERS
+#endif
+
+#include "pwqr.h"
+
+#define PWQR_HASH_BITS 5
+#define PWQR_HASH_SIZE (1 << PWQR_HASH_BITS)
+
+struct pwqr_task_bucket {
+ spinlock_t lock;
+ struct hlist_head tasks;
+};
+
+struct pwqr_sb {
+ struct kref kref;
+ struct rcu_head rcu;
+ wait_queue_head_t wqh;
+ pid_t tgid;
+
+ unsigned concurrency;
+ unsigned registered;
+
+ unsigned running;
+ unsigned waiting;
+ unsigned quarantined;
+ unsigned parked;
+ unsigned overcommit_wakes;
+
+ unsigned dead;
+};
+
+struct pwqr_task {
+ struct preempt_notifier notifier;
+ struct hlist_node link;
+ struct rcu_head rcu;
+ struct task_struct *task;
+ struct pwqr_sb *sb;
+};
+
+/*
+ * Global variables
+ */
+static struct class *pwqr_class;
+static int pwqr_major;
+static struct pwqr_task_bucket pwqr_tasks_hash[PWQR_HASH_SIZE];
+static struct preempt_ops pwqr_preempt_running_ops;
+static struct preempt_ops pwqr_preempt_blocked_ops;
+static struct preempt_ops pwqr_preempt_noop_ops;
+
+/*****************************************************************************
+ * Scoreboards
+ */
+
+#define pwqr_sb_lock_irqsave(sb, flags) \
+ spin_lock_irqsave(&(sb)->wqh.lock, flags)
+#define pwqr_sb_unlock_irqrestore(sb, flags) \
+ spin_unlock_irqrestore(&(sb)->wqh.lock, flags)
+
+static inline void __pwqr_sb_update_state(struct pwqr_sb *sb, int running_delta)
+{
+ int overcommit;
+
+ sb->running += running_delta;
+ overcommit = sb->running + sb->waiting - sb->concurrency;
+ if (overcommit == 0)
+ return;
+
+ if (overcommit > 0) {
+ if (overcommit > sb->waiting) {
+ sb->quarantined += sb->waiting;
+ sb->waiting = 0;
+ } else {
+ sb->quarantined += overcommit;
+ sb->waiting -= overcommit;
+ }
+ } else {
+ unsigned undercommit = -overcommit;
+
+ if (undercommit < sb->quarantined) {
+ sb->waiting += undercommit;
+ sb->quarantined -= undercommit;
+ } else if (sb->quarantined) {
+ sb->waiting += sb->quarantined;
+ sb->quarantined = 0;
+ } else if (sb->waiting == 0 && sb->parked) {
+ wake_up_locked(&sb->wqh);
+ }
+ }
+}
+
+static struct pwqr_sb *pwqr_sb_create(void)
+{
+ struct pwqr_sb *sb;
+
+ sb = kzalloc(sizeof(struct pwqr_sb), GFP_KERNEL);
+ if (sb == NULL)
+ return ERR_PTR(-ENOMEM);
+
+ kref_init(&sb->kref);
+ init_waitqueue_head(&sb->wqh);
+ sb->tgid = current->tgid;
+ sb->concurrency = num_online_cpus();
+
+ __module_get(THIS_MODULE);
+ return sb;
+}
+static inline void pwqr_sb_get(struct pwqr_sb *sb)
+{
+ kref_get(&sb->kref);
+}
+
+static void pwqr_sb_finalize(struct rcu_head *rcu)
+{
+ struct pwqr_sb *sb = container_of(rcu, struct pwqr_sb, rcu);
+
+ module_put(THIS_MODULE);
+ kfree(sb);
+}
+
+static void pwqr_sb_release(struct kref *kref)
+{
+ struct pwqr_sb *sb = container_of(kref, struct pwqr_sb, kref);
+
+ call_rcu(&sb->rcu, pwqr_sb_finalize);
+}
+static inline void pwqr_sb_put(struct pwqr_sb *sb)
+{
+ kref_put(&sb->kref, pwqr_sb_release);
+}
+
+/*****************************************************************************
+ * tasks
+ */
+static inline struct pwqr_task_bucket *task_hbucket(struct task_struct *task)
+{
+ return &pwqr_tasks_hash[hash_ptr(task, PWQR_HASH_BITS)];
+}
+
+static struct pwqr_task *pwqr_task_find(struct task_struct *task)
+{
+ struct pwqr_task_bucket *b = task_hbucket(task);
+ struct hlist_node *node;
+ struct pwqr_task *pwqt = NULL;
+
+ spin_lock(&b->lock);
+ hlist_for_each_entry(pwqt, node, &b->tasks, link) {
+ if (pwqt->task == task)
+ break;
+ }
+ spin_unlock(&b->lock);
+ return pwqt;
+}
+
+static struct pwqr_task *pwqr_task_create(struct task_struct *task)
+{
+ struct pwqr_task_bucket *b = task_hbucket(task);
+ struct pwqr_task *pwqt;
+
+ pwqt = kmalloc(sizeof(*pwqt), GFP_KERNEL);
+ if (pwqt == NULL)
+ return ERR_PTR(-ENOMEM);
+
+ preempt_notifier_init(&pwqt->notifier, &pwqr_preempt_running_ops);
+ preempt_notifier_register(&pwqt->notifier);
+ pwqt->task = task;
+
+ spin_lock(&b->lock);
+ hlist_add_head(&pwqt->link, &b->tasks);
+ spin_unlock(&b->lock);
+
+ return pwqt;
+}
+
+__cold
+static void pwqr_task_detach(struct pwqr_task *pwqt, struct pwqr_sb *sb)
+{
+ unsigned long flags;
+
+ pwqr_sb_lock_irqsave(sb, flags);
+ sb->registered--;
+ if (pwqt->notifier.ops == &pwqr_preempt_running_ops) {
+ __pwqr_sb_update_state(sb, -1);
+ } else {
+ __pwqr_sb_update_state(sb, 0);
+ }
+ pwqr_sb_unlock_irqrestore(sb, flags);
+ pwqr_sb_put(sb);
+ pwqt->sb = NULL;
+}
+
+__cold
+static void pwqr_task_attach(struct pwqr_task *pwqt, struct pwqr_sb *sb)
+{
+ unsigned long flags;
+
+ pwqr_sb_lock_irqsave(sb, flags);
+ pwqr_sb_get(pwqt->sb = sb);
+ sb->registered++;
+ __pwqr_sb_update_state(sb, 1);
+ pwqr_sb_unlock_irqrestore(sb, flags);
+}
+
+__cold
+static void pwqr_task_release(struct pwqr_task *pwqt, bool from_notifier)
+{
+ struct pwqr_task_bucket *b = task_hbucket(pwqt->task);
+
+ spin_lock(&b->lock);
+ hlist_del(&pwqt->link);
+ spin_unlock(&b->lock);
+ pwqt->notifier.ops = &pwqr_preempt_noop_ops;
+
+ if (from_notifier) {
+ /* When called from sched_{out,in}, it's not allowed to
+ * call preempt_notifier_unregister (or worse kfree())
+ *
+ * Though it's not a good idea to kfree() still registered
+ * callbacks if we're not dying, it'll panic on the next
+ * sched_{in,out} call.
+ */
+ BUG_ON(!(pwqt->task->state & TASK_DEAD));
+ kfree_rcu(pwqt, rcu);
+ } else {
+ preempt_notifier_unregister(&pwqt->notifier);
+ kfree(pwqt);
+ }
+}
+
+static void pwqr_task_noop_sched_in(struct preempt_notifier *notifier, int cpu)
+{
+}
+
+static void pwqr_task_noop_sched_out(struct preempt_notifier *notifier,
+ struct task_struct *next)
+{
+}
+
+static void pwqr_task_blocked_sched_in(struct preempt_notifier *notifier, int cpu)
+{
+ struct pwqr_task *pwqt = container_of(notifier, struct pwqr_task, notifier);
+ struct pwqr_sb *sb = pwqt->sb;
+ unsigned long flags;
+
+ if (unlikely(sb->dead)) {
+ pwqr_task_detach(pwqt, sb);
+ pwqr_task_release(pwqt, true);
+ return;
+ }
+
+ pwqt->notifier.ops = &pwqr_preempt_running_ops;
+ pwqr_sb_lock_irqsave(sb, flags);
+ __pwqr_sb_update_state(sb, 1);
+ pwqr_sb_unlock_irqrestore(sb, flags);
+}
+
+static void pwqr_task_sched_out(struct preempt_notifier *notifier,
+ struct task_struct *next)
+{
+ struct pwqr_task *pwqt = container_of(notifier, struct pwqr_task, notifier);
+ struct pwqr_sb *sb = pwqt->sb;
+ struct task_struct *p = pwqt->task;
+
+ if (unlikely(p->state & TASK_DEAD) || unlikely(sb->dead)) {
+ pwqr_task_detach(pwqt, sb);
+ pwqr_task_release(pwqt, true);
+ return;
+ }
+ if (p->state == 0 || (p->state & (__TASK_STOPPED | __TASK_TRACED)))
+ return;
+
+ pwqt->notifier.ops = &pwqr_preempt_blocked_ops;
+ /* see preempt.h: irq are disabled for sched_out */
+ spin_lock(&sb->wqh.lock);
+ __pwqr_sb_update_state(sb, -1);
+ spin_unlock(&sb->wqh.lock);
+}
+
+static struct preempt_ops __read_mostly pwqr_preempt_noop_ops = {
+ .sched_in = pwqr_task_noop_sched_in,
+ .sched_out = pwqr_task_noop_sched_out,
+};
+
+static struct preempt_ops __read_mostly pwqr_preempt_running_ops = {
+ .sched_in = pwqr_task_noop_sched_in,
+ .sched_out = pwqr_task_sched_out,
+};
+
+static struct preempt_ops __read_mostly pwqr_preempt_blocked_ops = {
+ .sched_in = pwqr_task_blocked_sched_in,
+ .sched_out = pwqr_task_sched_out,
+};
+
+/*****************************************************************************
+ * file descriptor
+ */
+static int pwqr_open(struct inode *inode, struct file *filp)
+{
+ struct pwqr_sb *sb;
+
+ sb = pwqr_sb_create();
+ if (IS_ERR(sb))
+ return PTR_ERR(sb);
+ filp->private_data = sb;
+ return 0;
+}
+
+static int pwqr_release(struct inode *inode, struct file *filp)
+{
+ struct pwqr_sb *sb = filp->private_data;
+ unsigned long flags;
+
+ pwqr_sb_lock_irqsave(sb, flags);
+ sb->dead = true;
+ pwqr_sb_unlock_irqrestore(sb, flags);
+ wake_up_all(&sb->wqh);
+ pwqr_sb_put(sb);
+ return 0;
+}
+
+static long
+do_pwqr_wait(struct pwqr_sb *sb, struct pwqr_task *pwqt,
+ int in_pool, struct pwqr_ioc_wait __user *arg)
+{
+ unsigned long flags;
+ struct pwqr_ioc_wait wait;
+ long rc = 0;
+ u32 uval;
+
+ preempt_notifier_unregister(&pwqt->notifier);
+
+ if (in_pool && copy_from_user(&wait, arg, sizeof(wait))) {
+ rc = -EFAULT;
+ goto out;
+ }
+
+ pwqr_sb_lock_irqsave(sb, flags);
+ if (sb->running + sb->waiting <= sb->concurrency) {
+ if (in_pool) {
+ while (probe_kernel_address(wait.pwqr_uaddr, uval)) {
+ pwqr_sb_unlock_irqrestore(sb, flags);
+ rc = get_user(uval, (u32 *)wait.pwqr_uaddr);
+ if (rc)
+ goto out;
+ pwqr_sb_lock_irqsave(sb, flags);
+ }
+
+ if (uval != (u32)wait.pwqr_ticket) {
+ rc = -EWOULDBLOCK;
+ goto out_unlock;
+ }
+ } else {
+ BUG_ON(sb->quarantined != 0);
+ goto out_unlock;
+ }
+ }
+
+ /* @ see <wait_event_interruptible_exclusive_locked_irq> */
+ if (likely(!sb->dead)) {
+ DEFINE_WAIT(__wait);
+
+ __wait.flags |= WQ_FLAG_EXCLUSIVE;
+
+ if (in_pool) {
+ sb->waiting++;
+ __add_wait_queue(&sb->wqh, &__wait);
+ } else {
+ sb->parked++;
+ __add_wait_queue_tail(&sb->wqh, &__wait);
+ }
+ __pwqr_sb_update_state(sb, -1);
+ set_current_state(TASK_INTERRUPTIBLE);
+
+ do {
+ if (sb->overcommit_wakes)
+ break;
+ if (signal_pending(current)) {
+ rc = -ERESTARTSYS;
+ break;
+ }
+ spin_unlock_irq(&sb->wqh.lock);
+ schedule();
+ spin_lock_irq(&sb->wqh.lock);
+ if (in_pool && sb->waiting)
+ break;
+ if (sb->running + sb->waiting < sb->concurrency)
+ break;
+ } while (likely(!sb->dead));
+
+ __remove_wait_queue(&sb->wqh, &__wait);
+ __set_current_state(TASK_RUNNING);
+
+ if (in_pool) {
+ if (sb->waiting) {
+ sb->waiting--;
+ } else {
+ BUG_ON(!sb->quarantined);
+ sb->quarantined--;
+ }
+ } else {
+ sb->parked--;
+ }
+ __pwqr_sb_update_state(sb, 1);
+ if (sb->overcommit_wakes)
+ sb->overcommit_wakes--;
+ if (sb->waiting + sb->running > sb->concurrency)
+ rc = -EDQUOT;
+ }
+
+out_unlock:
+ if (unlikely(sb->dead))
+ rc = -EBADFD;
+ pwqr_sb_unlock_irqrestore(sb, flags);
+out:
+ preempt_notifier_register(&pwqt->notifier);
+ return rc;
+}
+
+static long do_pwqr_unregister(struct pwqr_sb *sb, struct pwqr_task *pwqt)
+{
+ if (!pwqt)
+ return -EINVAL;
+ if (pwqt->sb != sb)
+ return -ENOENT;
+ pwqr_task_detach(pwqt, sb);
+ pwqr_task_release(pwqt, false);
+ return 0;
+}
+
+static long do_pwqr_set_conc(struct pwqr_sb *sb, int conc)
+{
+ long old_conc = sb->concurrency;
+ unsigned long flags;
+
+ pwqr_sb_lock_irqsave(sb, flags);
+ if (conc <= 0)
+ conc = num_online_cpus();
+ if (conc != old_conc) {
+ sb->concurrency = conc;
+ __pwqr_sb_update_state(sb, 0);
+ }
+ pwqr_sb_unlock_irqrestore(sb, flags);
+
+ return old_conc;
+}
+
+static long do_pwqr_wake(struct pwqr_sb *sb, int oc, int count)
+{
+ unsigned long flags;
+ int nwake;
+
+ if (count < 0)
+ return -EINVAL;
+
+ pwqr_sb_lock_irqsave(sb, flags);
+
+ if (oc) {
+ nwake = sb->waiting + sb->quarantined + sb->parked - sb->overcommit_wakes;
+ if (count > nwake) {
+ count = nwake;
+ } else {
+ nwake = count;
+ }
+ sb->overcommit_wakes += count;
+ } else if (sb->running + sb->overcommit_wakes < sb->concurrency) {
+ nwake = sb->concurrency - sb->overcommit_wakes - sb->running;
+ if (count > nwake) {
+ count = nwake;
+ } else {
+ nwake = count;
+ }
+ } else {
+ /*
+ * This codepath deserves an explanation: when the thread is
+ * quarantined, for is, really, it's already "parked". Though
+ * userland doesn't know about, so wake as many threads as
+ * userlands would have liked to, and let the wakeup tell
+ * userland those should be parked.
+ *
+ * That's why we lie about the number of woken threads,
+ * really, userlandwise we woke up a thread so that it could
+ * be parked for real and avoid spurious syscalls. So it's as
+ * if we woke up 0 threads.
+ */
+ nwake = sb->quarantined;
+ if (sb->waiting < sb->overcommit_wakes)
+ nwake -= sb->overcommit_wakes - sb->waiting;
+ if (nwake > count)
+ nwake = count;
+ count = 0;
+ }
+ while (nwake-- > 0)
+ wake_up_locked(&sb->wqh);
+ pwqr_sb_unlock_irqrestore(sb, flags);
+
+ return count;
+}
+
+static long pwqr_ioctl(struct file *filp, unsigned command, unsigned long arg)
+{
+ struct pwqr_sb *sb = filp->private_data;
+ struct task_struct *task = current;
+ struct pwqr_task *pwqt;
+ int rc = 0;
+
+ if (sb->tgid != current->tgid)
+ return -EBADFD;
+
+ switch (command) {
+ case PWQR_GET_CONC:
+ return sb->concurrency;
+ case PWQR_SET_CONC:
+ return do_pwqr_set_conc(sb, (int)arg);
+
+ case PWQR_WAKE:
+ case PWQR_WAKE_OC:
+ return do_pwqr_wake(sb, command == PWQR_WAKE_OC, (int)arg);
+
+ case PWQR_WAIT:
+ case PWQR_PARK:
+ case PWQR_REGISTER:
+ case PWQR_UNREGISTER:
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ pwqt = pwqr_task_find(task);
+ if (command == PWQR_UNREGISTER)
+ return do_pwqr_unregister(sb, pwqt);
+
+ if (pwqt == NULL) {
+ pwqt = pwqr_task_create(task);
+ if (IS_ERR(pwqt))
+ return PTR_ERR(pwqt);
+ pwqr_task_attach(pwqt, sb);
+ } else if (unlikely(pwqt->sb != sb)) {
+ pwqr_task_detach(pwqt, pwqt->sb);
+ pwqr_task_attach(pwqt, sb);
+ }
+
+ switch (command) {
+ case PWQR_WAIT:
+ rc = do_pwqr_wait(sb, pwqt, true, (struct pwqr_ioc_wait __user *)arg);
+ break;
+ case PWQR_PARK:
+ rc = do_pwqr_wait(sb, pwqt, false, NULL);
+ break;
+ }
+
+ if (unlikely(sb->dead)) {
+ pwqr_task_detach(pwqt, pwqt->sb);
+ return -EBADFD;
+ }
+ return rc;
+}
+
+static const struct file_operations pwqr_dev_fops = {
+ .owner = THIS_MODULE,
+ .open = pwqr_open,
+ .release = pwqr_release,
+ .unlocked_ioctl = pwqr_ioctl,
+#ifdef CONFIG_COMPAT
+ .compat_ioctl = pwqr_ioctl,
+#endif
+};
+
+/*****************************************************************************
+ * module
+ */
+static int __init pwqr_start(void)
+{
+ int i;
+
+ for (i = 0; i < PWQR_HASH_SIZE; i++) {
+ spin_lock_init(&pwqr_tasks_hash[i].lock);
+ INIT_HLIST_HEAD(&pwqr_tasks_hash[i].tasks);
+ }
+
+ /* Register as a character device */
+ pwqr_major = register_chrdev(0, "pwqr", &pwqr_dev_fops);
+ if (pwqr_major < 0) {
+ printk(KERN_ERR "pwqr: register_chrdev() failed\n");
+ return pwqr_major;
+ }
+
+ /* Create a device node */
+ pwqr_class = class_create(THIS_MODULE, PWQR_DEVICE_NAME);
+ if (IS_ERR(pwqr_class)) {
+ printk(KERN_ERR "pwqr: Error creating raw class\n");
+ unregister_chrdev(pwqr_major, PWQR_DEVICE_NAME);
+ return PTR_ERR(pwqr_class);
+ }
+ device_create(pwqr_class, NULL, MKDEV(pwqr_major, 0), NULL, PWQR_DEVICE_NAME);
+ printk(KERN_INFO "pwqr: PThreads Work Queues Regulator v1 loaded");
+ return 0;
+}
+
+static void __exit pwqr_end(void)
+{
+ rcu_barrier();
+ device_destroy(pwqr_class, MKDEV(pwqr_major, 0));
+ class_destroy(pwqr_class);
+ unregister_chrdev(pwqr_major, PWQR_DEVICE_NAME);
+}
+
+module_init(pwqr_start);
+module_exit(pwqr_end);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Pierre Habouzit <pierre.habouzit@intersec.com>");
+MODULE_DESCRIPTION("PThreads Work Queues Regulator");
+
+// vim:noet:sw=8:cinoptions+=\:0,L-1,=1s:
--- /dev/null
+ GNU LESSER GENERAL PUBLIC LICENSE
+ Version 2.1, February 1999
+
+ Copyright (C) 1991, 1999 Free Software Foundation, Inc.
+ 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ Everyone is permitted to copy and distribute verbatim copies
+ of this license document, but changing it is not allowed.
+
+[This is the first released version of the Lesser GPL. It also counts
+ as the successor of the GNU Library Public License, version 2, hence
+ the version number 2.1.]
+
+ Preamble
+
+ The licenses for most software are designed to take away your
+freedom to share and change it. By contrast, the GNU General Public
+Licenses are intended to guarantee your freedom to share and change
+free software--to make sure the software is free for all its users.
+
+ This license, the Lesser General Public License, applies to some
+specially designated software packages--typically libraries--of the
+Free Software Foundation and other authors who decide to use it. You
+can use it too, but we suggest you first think carefully about whether
+this license or the ordinary General Public License is the better
+strategy to use in any particular case, based on the explanations below.
+
+ When we speak of free software, we are referring to freedom of use,
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+
+ To protect your rights, we need to make restrictions that forbid
+distributors to deny you these rights or to ask you to surrender these
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+
+ For example, if you distribute copies of the library, whether gratis
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+
+ We protect your rights with a two-step method: (1) we copyright the
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+\f
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+ Most GNU software, including some libraries, is covered by the
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+
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+ <signature of Ty Coon>, 1 April 1990
+ Ty Coon, President of Vice
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+That's all there is to it!
--- /dev/null
+/*
+ * Copyright (C) 2012 Pierre Habouzit <pierre.habouzit@intersec.com>
+ * Copyright (C) 2012 Intersec SAS
+ *
+ * This file implements the Linux Pthread Workqueue Regulator usperspace.
+ *
+ * The Linux Pthread Workqueue Regulator is free software: you can
+ * redistribute it and/or modify it under the terms of the GNU Lesser
+ * General Public License as published by the Free Software Foundation,
+ * either version 2.1 of the License, or (at your option) any later version.
+ *
+ * The Linux Pthread Workqueue Regulator is distributed in the hope that it
+ * will be useful, but WITHOUT ANY WARRANTY; without even the implied
+ * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with The Linux Pthread Workqueue Regultaor.
+ * If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <assert.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <pthread.h>
+#include <sched.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <sys/ioctl.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include "../kernel/pwqr.h"
+
+#define INPOOL 0
+#define PARKED 1
+#define PARKED_MAX 16
+#define THREADS_MAX 128 /* something dynamic is probably better */
+
+/* Compiler stuff {{{ */
+
+#if defined(__x86_64__)
+# define mb() asm volatile("mfence":::"memory")
+#elif defined(__i386__)
+# define mb() asm volatile("lock; addl $0,0(%%esp)":::"memory")
+#else
+# error unsupported architecture
+#endif
+
+#define container_of(obj, type_t, member) \
+ ({ const typeof(((type_t *)0)->member) *__mptr = (obj); \
+ ((type_t *)((char *)__mptr) - offsetof(type_t, member)); })
+#define likely(expr) __builtin_expect(!!(expr), 1)
+#define unlikely(expr) __builtin_expect((expr), 0)
+
+#define barrier() asm volatile("":::"memory")
+#define access_once(x) (*(volatile typeof(x) *)&(x))
+
+#define atomic_fetch_and_add(ptr, n) __sync_fetch_and_add(ptr, n)
+#define atomic_add(ptr, n) (void)atomic_fetch_and_add(ptr, n)
+#define atomic_fetch_and_sub(ptr, n) __sync_fetch_and_sub(ptr, n)
+#define atomic_sub(ptr, n) (void)atomic_fetch_and_sub(ptr, n)
+
+#define ALWAYS_INLINE __attribute__((always_inline)) inline
+
+/* }}} */
+/* pwqr wrapping {{{ */
+
+static int pwqr_create(void)
+{
+ return open("/dev/"PWQR_DEVICE_NAME, O_RDWR);
+}
+
+static int pwqr_ctl(int fd, int op, int val, void *uaddr)
+{
+ struct pwqr_ioc_wait wait;
+
+ switch (op) {
+ case PWQR_GET_CONC:
+ case PWQR_REGISTER:
+ case PWQR_UNREGISTER:
+ case PWQR_PARK:
+ return ioctl(fd, op);
+ case PWQR_SET_CONC:
+ case PWQR_WAKE:
+ case PWQR_WAKE_OC:
+ return ioctl(fd, op, val);
+ case PWQR_WAIT:
+ wait.pwqr_ticket = val;
+ wait.pwqr_uaddr = uaddr;
+ return ioctl(fd, op, &wait);
+ default:
+ errno = EINVAL;
+ return -1;
+ }
+}
+
+/* }}} */
+
+static struct {
+ int fd;
+ /* atomic */ int spinlock;
+ /* atomic */ int nthreads;
+ /* atomic */ int waiters;
+ /* atomic */ int parked;
+
+ union {
+ struct {
+#if __BYTE_ORDER == __LITTLE_ENDIAN
+ /* atomic */ uint32_t lo;
+ /* atomic */ uint32_t hi;
+#elif __BYTE_ORDER == __BIG_ENDIAN
+ /* atomic */ uint32_t hi;
+ /* atomic */ uint32_t lo;
+#else
+#error Unsupported endianness
+#endif
+ };
+ uint64_t ticket;
+ };
+} pwqr_g = {
+ .fd = -1,
+};
+
+static ALWAYS_INLINE void pwqr_lock(void)
+{
+ while (unlikely(__sync_lock_test_and_set(&pwqr_g.spinlock, 1)))
+ sched_yield();
+}
+
+static ALWAYS_INLINE void pwqr_unlock(void)
+{
+ __sync_lock_release(&pwqr_g.spinlock);
+}
+
+static ALWAYS_INLINE uint64_t pwqr_get_ticket(void)
+{
+ mb();
+ return access_once(pwqr_g.ticket);
+}
+
+static ALWAYS_INLINE void pwqr_signal_n(int n)
+{
+#if ULONG_MAX == UINT32_MAX
+ /*
+ * We don't know how slow things are between a pwqr_get() and a
+ * pwqr_wait. Hence it's not safe to assume the "count" will never
+ * rotate fully between the two.
+ *
+ * In 64bits mode, well, we have 64-bits atomic increments and all is
+ * fine. In 32bits mode, we increment the high word manually every 2^24
+ * low-word increment.
+ *
+ * This assumes that at least one of the 256 threads that will try to
+ * perform the "hi" increment won't be stalled between deciding the modulo
+ * is zero and the increment itself for an almost full cycle (2^32 - 2^24)
+ * of the low word counter.
+ */
+ if (unlikely(atomic_fetch_and_add(&pwqr_g.lo, 1) % (1U << 24) == 0))
+ atomic_add(&pwqr_g.hi, 1);
+#else
+ atomic_add(&pwqr_g.ticket, 1);
+#endif
+ if (atomic_fetch_and_add(&pwqr_g.waiters, 0))
+ pwqr_ctl(pwqr_g.fd, PWQR_WAKE, n, NULL);
+}
+static ALWAYS_INLINE void pwqr_signal(void)
+{
+ pwqr_signal_n(1);
+}
+
+static ALWAYS_INLINE void pwqr_signal_relaxed_n(int n)
+{
+ if (access_once(pwqr_g.waiters))
+ pwqr_signal_n(n);
+}
+static ALWAYS_INLINE void pwqr_signal_relaxed(void)
+{
+ pwqr_signal_relaxed_n(1);
+}
+
+
+/* returns:
+ - INPOOL if we were woken to run jobs.
+ - PARKED if we were woken to be parked (possibly consume overcommit stuff)
+ */
+static void pwqr_do_wait_cleanup(void *arg)
+{
+ atomic_sub(&pwqr_g.waiters, 1);
+}
+static int pwqr_do_wait(uint64_t ticket)
+{
+ int canceltype, rc;
+
+ mb();
+#if ULONG_MAX == UINT32_MAX
+ if ((unsigned)(ticket >> 32) != access_once(pwqr_g.hi))
+ return INPOOL;
+#else
+ if (ticket != access_once(pwqr_g.ticket))
+ return INPOOL;
+#endif
+
+ atomic_add(&pwqr_g.waiters, 1);
+ pthread_cleanup_push(&pwqr_do_wait_cleanup, NULL);
+ pthread_setcanceltype(PTHREAD_CANCEL_ASYNCHRONOUS, &canceltype);
+
+ rc = pwqr_ctl(pwqr_g.fd, PWQR_WAIT, ticket, &pwqr_g.lo);
+ if (rc < 0) {
+ if (errno == EINTR) {
+ rc = INPOOL;
+ } else if (errno == EDQUOT) {
+ rc = PARKED;
+ } else {
+ assert (errno == EBADFD);
+ }
+ }
+
+ pthread_setcanceltype(canceltype, NULL);
+ pthread_cleanup_pop(1);
+}
+
+/* returns INPOOL if the thread is to run some jobs or go to WAIT
+ * returns -1 if the pwqr_g.fd is broken
+ */
+static void pwqr_do_park_cleanup(void *arg)
+{
+ atomic_sub(&pwqr_g.parked, 1);
+}
+static void pwqr_spawn_thread(int initial_state, int count);
+static int pwqr_do_park(void)
+{
+ int canceltype, rc = -1;
+
+ if (atomic_fetch_and_add(&pwqr_g.parked, 1) > PARKED_MAX) {
+ atomic_sub(&pwqr_g.parked, 1);
+ return -1;
+ }
+
+ pthread_cleanup_push(&pwqr_do_park_cleanup, NULL);
+ pthread_setcanceltype(PTHREAD_CANCEL_ASYNCHRONOUS, &canceltype);
+
+ for (;;) {
+#ifdef PSEUDO_CODE
+ while ((job = find_some_job(OC_JOB)))
+ run_job(job);
+#endif
+
+ if ((rc = pwqr_ctl(pwqr_g.fd, PWQR_PARK, 0, NULL)) == 0) {
+ if (atomic_fetch_and_sub(&pwqr_g.parked, 1) == 0) {
+ pwqr_spawn_thread(PARKED, 1);
+ }
+ break;
+ }
+
+ if (rc < 0) {
+ if (errno == EBADFD) {
+ atomic_sub(&pwqr_g.parked, 1);
+ return -1;
+ }
+ assert (errno == EINTR || errno == EDQUOT);
+ continue;
+ }
+ }
+
+ pthread_setcanceltype(canceltype, NULL);
+ pthread_cleanup_pop(0);
+ return rc;
+}
+
+static void pwqr_main_cleanup(void *arg)
+{
+ atomic_sub(&pwqr_g.nthreads, 1);
+}
+static void *pwqr_main(void *arg)
+{
+ int state = (long)arg;
+
+ if (atomic_fetch_and_add(&pwqr_g.nthreads, 1) > THREADS_MAX)
+ goto out;
+
+ pthread_cleanup_push(&pwqr_main_cleanup, NULL);
+ if (pwqr_ctl(pwqr_g.fd, PWQR_REGISTER, 0, NULL) < 0)
+ goto out;
+
+ do {
+ uint64_t ticket;
+
+ if (state == PARKED && (state = pwqr_do_park()) < 0)
+ break;
+#ifdef PSEUDO_CODE
+ while ((job = find_some_job(ANY_JOB)))
+ run_job(job);
+#endif
+ ticket = pwqr_get_ticket();
+#ifdef PSEUDO_CODE
+ if ((job = find_some_job(ANY_JOB))) {
+ run_job(job);
+ continue;
+ }
+#endif
+ state = pwqr_do_wait(ticket);
+ } while (state >= 0);
+
+ out:
+ pthread_cleanup_pop(1);
+ return NULL;
+}
+
+static void pwqr_spawn_thread(int initial_state, int count)
+{
+ pthread_t thr;
+ pthread_attr_t attr;
+
+ pthread_attr_init(&attr);
+ pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
+ while (count-- > 0)
+ pthread_create(&thr, &attr, pwqr_main, (void *)(long)initial_state);
+ pthread_attr_destroy(&attr);
+}
+
+__attribute__((cold, noinline, unused))
+static int _pthread_workqueue_init_np(void)
+{
+ int rc = 0, fd, n;
+
+ pwqr_lock();
+ if (pwqr_g.fd >= 0)
+ goto out;
+
+ fd = pwqr_create();
+ if (fd < 0) {
+ rc = -1;
+ goto out;
+ }
+
+ pwqr_g.fd = fd;
+ n = pwqr_ctl(pwqr_g.fd, PWQR_GET_CONC, 0, NULL) + 4;
+ pwqr_spawn_thread(INPOOL, n);
+ pwqr_spawn_thread(PARKED, 4);
+
+ out:
+ pwqr_unlock();
+ return rc;
+}