Pthread Workqueue Regulator (pwqr) initial commit.

This contains an alpha/beta quality kernel proof-of-concept driver, plus
some code concepts to wrap the syscall in lib/libpwqr.c

Signed-off-by: Pierre Habouzit <pierre.habouzit@intersec.com>

diff --git a/.gitignore b/.gitignore
new file mode 100644 (file)
index 0000000..32058e5
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,8 @@
+*.o
+*.ko
+*.so
+*.mod.c
+.*.cmd
+.tmp_versions
+Module.symvers
+modules.order

diff --git a/Makefile b/Makefile
new file mode 100644 (file)
index 0000000..7558a97
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,5 @@
+all clean:
+       $(MAKE) -C kernel $@
+       $(MAKE) -C lib $@
+
+.PHONY: all clean

diff --git a/kernel/Makefile b/kernel/Makefile
new file mode 100644 (file)
index 0000000..94c9f88
--- /dev/null
+++ b/kernel/Makefile
@@ -0,0 +1,14 @@
+KVERSION = $(shell uname -r)
+
+obj-m = pwqr.o
+
+all: pwqr.ko
+
+pwqr.ko: pwqr.c pwqr.h
+       $(MAKE) -C /lib/modules/$(KVERSION)/build M=$(PWD) modules
+
+clean:
+       $(MAKE) -C /lib/modules/$(KVERSION)/build M=$(PWD) clean
+       $(RM) test
+
+.PHONY: all clean

diff --git a/kernel/pwqr.c b/kernel/pwqr.c
new file mode 100644 (file)
index 0000000..0dd026f
--- /dev/null
+++ b/kernel/pwqr.c
@@ -0,0 +1,648 @@
+/*
+ * 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:

diff --git a/kernel/pwqr.h b/kernel/pwqr.h
new file mode 100644 (file)
index 0000000..a7aa086
--- /dev/null
+++ b/kernel/pwqr.h
@@ -0,0 +1,42 @@
+/*
+ * 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/>.
+ */
+
+#ifndef _LINUX_PWQR_H
+#define _LINUX_PWQR_H
+#include <linux/ioctl.h>
+
+#define PWQR_DEVICE_NAME       "pwq"
+#define PWQR_IO                        '}'
+
+struct pwqr_ioc_wait {
+       int     pwqr_ticket;
+       void   *pwqr_uaddr;
+};
+
+#define PWQR_GET_CONC          _IO (PWQR_IO, 0)
+#define PWQR_SET_CONC          _IO (PWQR_IO, 1)
+#define PWQR_REGISTER          _IO (PWQR_IO, 2)
+#define PWQR_UNREGISTER                _IO (PWQR_IO, 3)
+#define PWQR_WAKE              _IO (PWQR_IO, 4)
+#define PWQR_WAKE_OC           _IO (PWQR_IO, 5)
+#define PWQR_WAIT              _IOW(PWQR_IO, 6, struct pwqr_ioc_wait)
+#define PWQR_PARK              _IO (PWQR_IO, 7)
+
+#endif

diff --git a/lib/COPYING b/lib/COPYING
new file mode 100644 (file)
index 0000000..4362b49
--- /dev/null
+++ b/lib/COPYING
@@ -0,0 +1,502 @@
+                  GNU LESSER GENERAL PUBLIC LICENSE
+                       Version 2.1, February 1999
+
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diff --git a/lib/Makefile b/lib/Makefile
new file mode 100644 (file)
index 0000000..814ba75
--- /dev/null
+++ b/lib/Makefile
@@ -0,0 +1,9 @@
+all: libpwqr.so
+
+libpwqr.so: libpwqr.c
+       $(CC) -Wall -Werror -Wextra -Wno-unused-parameter $(CFLAGS) -O2 -fPIC -g -shared -lpthread -o $@ $<
+
+clean:
+       $(RM) libpwqr.so
+
+.PHONY: all clean

diff --git a/lib/libpwqr.c b/lib/libpwqr.c
new file mode 100644 (file)
index 0000000..f5d53a2
--- /dev/null
+++ b/lib/libpwqr.c
@@ -0,0 +1,345 @@
+/*
+ * 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;
+}