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Commit 181a51f6 authored by Tejun Heo's avatar Tejun Heo
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slow-work: kill it 

slow-work doesn't have any user left.  Kill it.
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarDavid Howells <dhowells@redhat.com>
parent 6ecd7c2d
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====================================
SLOW WORK ITEM EXECUTION THREAD POOL
====================================
By: David Howells <dhowells@redhat.com>
The slow work item execution thread pool is a pool of threads for performing
things that take a relatively long time, such as making mkdir calls.
Typically, when processing something, these items will spend a lot of time
blocking a thread on I/O, thus making that thread unavailable for doing other
work.
The standard workqueue model is unsuitable for this class of work item as that
limits the owner to a single thread or a single thread per CPU. For some
tasks, however, more threads - or fewer - are required.
There is just one pool per system. It contains no threads unless something
wants to use it - and that something must register its interest first. When
the pool is active, the number of threads it contains is dynamic, varying
between a maximum and minimum setting, depending on the load.
====================
CLASSES OF WORK ITEM
====================
This pool support two classes of work items:
(*) Slow work items.
(*) Very slow work items.
The former are expected to finish much quicker than the latter.
An operation of the very slow class may do a batch combination of several
lookups, mkdirs, and a create for instance.
An operation of the ordinarily slow class may, for example, write stuff or
expand files, provided the time taken to do so isn't too long.
Operations of both types may sleep during execution, thus tying up the thread
loaned to it.
A further class of work item is available, based on the slow work item class:
(*) Delayed slow work items.
These are slow work items that have a timer to defer queueing of the item for
a while.
THREAD-TO-CLASS ALLOCATION
--------------------------
Not all the threads in the pool are available to work on very slow work items.
The number will be between one and one fewer than the number of active threads.
This is configurable (see the "Pool Configuration" section).
All the threads are available to work on ordinarily slow work items, but a
percentage of the threads will prefer to work on very slow work items.
The configuration ensures that at least one thread will be available to work on
very slow work items, and at least one thread will be available that won't work
on very slow work items at all.
=====================
USING SLOW WORK ITEMS
=====================
Firstly, a module or subsystem wanting to make use of slow work items must
register its interest:
int ret = slow_work_register_user(struct module *module);
This will return 0 if successful, or a -ve error upon failure. The module
pointer should be the module interested in using this facility (almost
certainly THIS_MODULE).
Slow work items may then be set up by:
(1) Declaring a slow_work struct type variable:
#include <linux/slow-work.h>
struct slow_work myitem;
(2) Declaring the operations to be used for this item:
struct slow_work_ops myitem_ops = {
.get_ref = myitem_get_ref,
.put_ref = myitem_put_ref,
.execute = myitem_execute,
};
[*] For a description of the ops, see section "Item Operations".
(3) Initialising the item:
slow_work_init(&myitem, &myitem_ops);
or:
delayed_slow_work_init(&myitem, &myitem_ops);
or:
vslow_work_init(&myitem, &myitem_ops);
depending on its class.
A suitably set up work item can then be enqueued for processing:
int ret = slow_work_enqueue(&myitem);
This will return a -ve error if the thread pool is unable to gain a reference
on the item, 0 otherwise, or (for delayed work):
int ret = delayed_slow_work_enqueue(&myitem, my_jiffy_delay);
The items are reference counted, so there ought to be no need for a flush
operation. But as the reference counting is optional, means to cancel
existing work items are also included:
cancel_slow_work(&myitem);
cancel_delayed_slow_work(&myitem);
can be used to cancel pending work. The above cancel function waits for
existing work to have been executed (or prevent execution of them, depending
on timing).
When all a module's slow work items have been processed, and the
module has no further interest in the facility, it should unregister its
interest:
slow_work_unregister_user(struct module *module);
The module pointer is used to wait for all outstanding work items for that
module before completing the unregistration. This prevents the put_ref() code
from being taken away before it completes. module should almost certainly be
THIS_MODULE.
================
HELPER FUNCTIONS
================
The slow-work facility provides a function by which it can be determined
whether or not an item is queued for later execution:
bool queued = slow_work_is_queued(struct slow_work *work);
If it returns false, then the item is not on the queue (it may be executing
with a requeue pending). This can be used to work out whether an item on which
another depends is on the queue, thus allowing a dependent item to be queued
after it.
If the above shows an item on which another depends not to be queued, then the
owner of the dependent item might need to wait. However, to avoid locking up
the threads unnecessarily be sleeping in them, it can make sense under some
circumstances to return the work item to the queue, thus deferring it until
some other items have had a chance to make use of the yielded thread.
To yield a thread and defer an item, the work function should simply enqueue
the work item again and return. However, this doesn't work if there's nothing
actually on the queue, as the thread just vacated will jump straight back into
the item's work function, thus busy waiting on a CPU.
Instead, the item should use the thread to wait for the dependency to go away,
but rather than using schedule() or schedule_timeout() to sleep, it should use
the following function:
bool requeue = slow_work_sleep_till_thread_needed(
struct slow_work *work,
signed long *_timeout);
This will add a second wait and then sleep, such that it will be woken up if
either something appears on the queue that could usefully make use of the
thread - and behind which this item can be queued, or if the event the caller
set up to wait for happens. True will be returned if something else appeared
on the queue and this work function should perhaps return, of false if
something else woke it up. The timeout is as for schedule_timeout().
For example:
wq = bit_waitqueue(&my_flags, MY_BIT);
init_wait(&wait);
requeue = false;
do {
prepare_to_wait(wq, &wait, TASK_UNINTERRUPTIBLE);
if (!test_bit(MY_BIT, &my_flags))
break;
requeue = slow_work_sleep_till_thread_needed(&my_work,
&timeout);
} while (timeout > 0 && !requeue);
finish_wait(wq, &wait);
if (!test_bit(MY_BIT, &my_flags)
goto do_my_thing;
if (requeue)
return; // to slow_work
===============
ITEM OPERATIONS
===============
Each work item requires a table of operations of type struct slow_work_ops.
Only ->execute() is required; the getting and putting of a reference and the
describing of an item are all optional.
(*) Get a reference on an item:
int (*get_ref)(struct slow_work *work);
This allows the thread pool to attempt to pin an item by getting a
reference on it. This function should return 0 if the reference was
granted, or a -ve error otherwise. If an error is returned,
slow_work_enqueue() will fail.
The reference is held whilst the item is queued and whilst it is being
executed. The item may then be requeued with the same reference held, or
the reference will be released.
(*) Release a reference on an item:
void (*put_ref)(struct slow_work *work);
This allows the thread pool to unpin an item by releasing the reference on
it. The thread pool will not touch the item again once this has been
called.
(*) Execute an item:
void (*execute)(struct slow_work *work);
This should perform the work required of the item. It may sleep, it may
perform disk I/O and it may wait for locks.
(*) View an item through /proc:
void (*desc)(struct slow_work *work, struct seq_file *m);
If supplied, this should print to 'm' a small string describing the work
the item is to do. This should be no more than about 40 characters, and
shouldn't include a newline character.
See the 'Viewing executing and queued items' section below.
==================
POOL CONFIGURATION
==================
The slow-work thread pool has a number of configurables:
(*) /proc/sys/kernel/slow-work/min-threads
The minimum number of threads that should be in the pool whilst it is in
use. This may be anywhere between 2 and max-threads.
(*) /proc/sys/kernel/slow-work/max-threads
The maximum number of threads that should in the pool. This may be
anywhere between min-threads and 255 or NR_CPUS * 2, whichever is greater.
(*) /proc/sys/kernel/slow-work/vslow-percentage
The percentage of active threads in the pool that may be used to execute
very slow work items. This may be between 1 and 99. The resultant number
is bounded to between 1 and one fewer than the number of active threads.
This ensures there is always at least one thread that can process very
slow work items, and always at least one thread that won't.
==================================
VIEWING EXECUTING AND QUEUED ITEMS
==================================
If CONFIG_SLOW_WORK_DEBUG is enabled, a debugfs file is made available:
/sys/kernel/debug/slow_work/runqueue
through which the list of work items being executed and the queues of items to
be executed may be viewed. The owner of a work item is given the chance to
add some information of its own.
The contents look something like the following:
THR PID ITEM ADDR FL MARK DESC
=== ===== ================ == ===== ==========
0 3005 ffff880023f52348 a 952ms FSC: OBJ17d3: LOOK
1 3006 ffff880024e33668 2 160ms FSC: OBJ17e5 OP60d3b: Write1/Store fl=2
2 3165 ffff8800296dd180 a 424ms FSC: OBJ17e4: LOOK
3 4089 ffff8800262c8d78 a 212ms FSC: OBJ17ea: CRTN
4 4090 ffff88002792bed8 2 388ms FSC: OBJ17e8 OP60d36: Write1/Store fl=2
5 4092 ffff88002a0ef308 2 388ms FSC: OBJ17e7 OP60d2e: Write1/Store fl=2
6 4094 ffff88002abaf4b8 2 132ms FSC: OBJ17e2 OP60d4e: Write1/Store fl=2
7 4095 ffff88002bb188e0 a 388ms FSC: OBJ17e9: CRTN
vsq - ffff880023d99668 1 308ms FSC: OBJ17e0 OP60f91: Write1/EnQ fl=2
vsq - ffff8800295d1740 1 212ms FSC: OBJ16be OP4d4b6: Write1/EnQ fl=2
vsq - ffff880025ba3308 1 160ms FSC: OBJ179a OP58dec: Write1/EnQ fl=2
vsq - ffff880024ec83e0 1 160ms FSC: OBJ17ae OP599f2: Write1/EnQ fl=2
vsq - ffff880026618e00 1 160ms FSC: OBJ17e6 OP60d33: Write1/EnQ fl=2
vsq - ffff880025a2a4b8 1 132ms FSC: OBJ16a2 OP4d583: Write1/EnQ fl=2
vsq - ffff880023cbe6d8 9 212ms FSC: OBJ17eb: LOOK
vsq - ffff880024d37590 9 212ms FSC: OBJ17ec: LOOK
vsq - ffff880027746cb0 9 212ms FSC: OBJ17ed: LOOK
vsq - ffff880024d37ae8 9 212ms FSC: OBJ17ee: LOOK
vsq - ffff880024d37cb0 9 212ms FSC: OBJ17ef: LOOK
vsq - ffff880025036550 9 212ms FSC: OBJ17f0: LOOK
vsq - ffff8800250368e0 9 212ms FSC: OBJ17f1: LOOK
vsq - ffff880025036aa8 9 212ms FSC: OBJ17f2: LOOK
In the 'THR' column, executing items show the thread they're occupying and
queued threads indicate which queue they're on. 'PID' shows the process ID of
a slow-work thread that's executing something. 'FL' shows the work item flags.
'MARK' indicates how long since an item was queued or began executing. Lastly,
the 'DESC' column permits the owner of an item to give some information.
include/linux/slow-work.h deleted 100644 → 0
View file @ 6ecd7c2d
/* Worker thread pool for slow items, such as filesystem lookups or mkdirs
*
* Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public Licence
* as published by the Free Software Foundation; either version
* 2 of the Licence, or (at your option) any later version.
*
* See Documentation/slow-work.txt
*/
#ifndef _LINUX_SLOW_WORK_H
#define _LINUX_SLOW_WORK_H
#ifdef CONFIG_SLOW_WORK
#include <linux/sysctl.h>
#include <linux/timer.h>
struct slow_work;
#ifdef CONFIG_SLOW_WORK_DEBUG
struct seq_file;
#endif
/*
* The operations used to support slow work items
*/
struct slow_work_ops {
/* owner */
struct module *owner;
/* get a ref on a work item
* - return 0 if successful, -ve if not
*/
int (*get_ref)(struct slow_work *work);
/* discard a ref to a work item */
void (*put_ref)(struct slow_work *work);
/* execute a work item */
void (*execute)(struct slow_work *work);
#ifdef CONFIG_SLOW_WORK_DEBUG
/* describe a work item for debugfs */
void (*desc)(struct slow_work *work, struct seq_file *m);
#endif
};
/*
* A slow work item
* - A reference is held on the parent object by the thread pool when it is
* queued
*/
struct slow_work {
struct module *owner; /* the owning module */
unsigned long flags;
#define SLOW_WORK_PENDING 0 /* item pending (further) execution */
#define SLOW_WORK_EXECUTING 1 /* item currently executing */
#define SLOW_WORK_ENQ_DEFERRED 2 /* item enqueue deferred */
#define SLOW_WORK_VERY_SLOW 3 /* item is very slow */
#define SLOW_WORK_CANCELLING 4 /* item is being cancelled, don't enqueue */
#define SLOW_WORK_DELAYED 5 /* item is struct delayed_slow_work with active timer */
const struct slow_work_ops *ops; /* operations table for this item */
struct list_head link; /* link in queue */
#ifdef CONFIG_SLOW_WORK_DEBUG
struct timespec mark; /* jiffies at which queued or exec begun */
#endif
};
struct delayed_slow_work {
struct slow_work work;
struct timer_list timer;
};
/**
* slow_work_init - Initialise a slow work item
* @work: The work item to initialise
* @ops: The operations to use to handle the slow work item
*
* Initialise a slow work item.
*/
static inline void slow_work_init(struct slow_work *work,
const struct slow_work_ops *ops)
{
work->flags = 0;
work->ops = ops;
INIT_LIST_HEAD(&work->link);
}
/**
* slow_work_init - Initialise a delayed slow work item
* @work: The work item to initialise
* @ops: The operations to use to handle the slow work item
*
* Initialise a delayed slow work item.
*/
static inline void delayed_slow_work_init(struct delayed_slow_work *dwork,
const struct slow_work_ops *ops)
{
init_timer(&dwork->timer);
slow_work_init(&dwork->work, ops);
}
/**
* vslow_work_init - Initialise a very slow work item
* @work: The work item to initialise
* @ops: The operations to use to handle the slow work item
*
* Initialise a very slow work item. This item will be restricted such that
* only a certain number of the pool threads will be able to execute items of
* this type.
*/
static inline void vslow_work_init(struct slow_work *work,
const struct slow_work_ops *ops)
{
work->flags = 1 << SLOW_WORK_VERY_SLOW;
work->ops = ops;
INIT_LIST_HEAD(&work->link);
}
/**
* slow_work_is_queued - Determine if a slow work item is on the work queue
* work: The work item to test
*
* Determine if the specified slow-work item is on the work queue. This
* returns true if it is actually on the queue.
*
* If the item is executing and has been marked for requeue when execution
* finishes, then false will be returned.
*
* Anyone wishing to wait for completion of execution can wait on the
* SLOW_WORK_EXECUTING bit.
*/
static inline bool slow_work_is_queued(struct slow_work *work)
{
unsigned long flags = work->flags;
return flags & SLOW_WORK_PENDING && !(flags & SLOW_WORK_EXECUTING);
}
extern int slow_work_enqueue(struct slow_work *work);
extern void slow_work_cancel(struct slow_work *work);
extern int slow_work_register_user(struct module *owner);
extern void slow_work_unregister_user(struct module *owner);
extern int delayed_slow_work_enqueue(struct delayed_slow_work *dwork,
unsigned long delay);
static inline void delayed_slow_work_cancel(struct delayed_slow_work *dwork)
{
slow_work_cancel(&dwork->work);
}
extern bool slow_work_sleep_till_thread_needed(struct slow_work *work,
signed long *_timeout);
#ifdef CONFIG_SYSCTL
extern ctl_table slow_work_sysctls[];
#endif
#endif /* CONFIG_SLOW_WORK */
#endif /* _LINUX_SLOW_WORK_H */
init/Kconfig
View file @ 181a51f6
......@@ -1143,30 +1143,6 @@ config TRACEPOINTS
source "arch/Kconfig"
config SLOW_WORK
default n
bool
help
The slow work thread pool provides a number of dynamically allocated
threads that can be used by the kernel to perform operations that
take a relatively long time.
An example of this would be CacheFiles doing a path lookup followed
by a series of mkdirs and a create call, all of which have to touch
disk.
See Documentation/slow-work.txt.
config SLOW_WORK_DEBUG
bool "Slow work debugging through debugfs"
default n
depends on SLOW_WORK && DEBUG_FS
help
Display the contents of the slow work run queue through debugfs,
including items currently executing.
See Documentation/slow-work.txt.
endmenu # General setup
config HAVE_GENERIC_DMA_COHERENT
......
kernel/Makefile
View file @ 181a51f6
......@@ -99,8 +99,6 @@ obj-$(CONFIG_TRACING) += trace/
obj-$(CONFIG_X86_DS) += trace/
obj-$(CONFIG_RING_BUFFER) += trace/
obj-$(CONFIG_SMP) += sched_cpupri.o
obj-$(CONFIG_SLOW_WORK) += slow-work.o
obj-$(CONFIG_SLOW_WORK_DEBUG) += slow-work-debugfs.o
obj-$(CONFIG_PERF_EVENTS) += perf_event.o
obj-$(CONFIG_HAVE_HW_BREAKPOINT) += hw_breakpoint.o
obj-$(CONFIG_USER_RETURN_NOTIFIER) += user-return-notifier.o
......
kernel/slow-work-debugfs.c deleted 100644 → 0
View file @ 6ecd7c2d
/* Slow work debugging
*
* Copyright (C) 2009 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public Licence
* as published by the Free Software Foundation; either version
* 2 of the Licence, or (at your option) any later version.
*/
#include <linux/module.h>
#include <linux/slow-work.h>
#include <linux/fs.h>
#include <linux/time.h>
#include <linux/seq_file.h>
#include "slow-work.h"
#define ITERATOR_SHIFT (BITS_PER_LONG - 4)
#define ITERATOR_SELECTOR (0xfUL << ITERATOR_SHIFT)
#define ITERATOR_COUNTER (~ITERATOR_SELECTOR)
void slow_work_new_thread_desc(struct slow_work *work, struct seq_file *m)
{
seq_puts(m, "Slow-work: New thread");
}
/*
* Render the time mark field on a work item into a 5-char time with units plus
* a space
*/
static void slow_work_print_mark(struct seq_file *m, struct slow_work *work)
{
struct timespec now, diff;
now = CURRENT_TIME;
diff = timespec_sub(now, work->mark);
if (diff.tv_sec < 0)
seq_puts(m, " -ve ");
else if (diff.tv_sec == 0 && diff.tv_nsec < 1000)
seq_printf(m, "%3luns ", diff.tv_nsec);
else if (diff.tv_sec == 0 && diff.tv_nsec < 1000000)
seq_printf(m, "%3luus ", diff.tv_nsec / 1000);
else if (diff.tv_sec == 0 && diff.tv_nsec < 1000000000)
seq_printf(m, "%3lums ", diff.tv_nsec / 1000000);
else if (diff.tv_sec <= 1)
seq_puts(m, " 1s ");
else if (diff.tv_sec < 60)
seq_printf(m, "%4lus ", diff.tv_sec);
else if (diff.tv_sec < 60 * 60)
seq_printf(m, "%4lum ", diff.tv_sec / 60);
else if (diff.tv_sec < 60 * 60 * 24)
seq_printf(m, "%4luh ", diff.tv_sec / 3600);
else
seq_puts(m, "exces ");
}
/*
* Describe a slow work item for debugfs
*/
static int slow_work_runqueue_show(struct seq_file *m, void *v)
{
struct slow_work *work;
struct list_head *p = v;
unsigned long id;
switch ((unsigned long) v) {
case 1:
seq_puts(m, "THR PID ITEM ADDR FL MARK DESC\n");
return 0;
case 2:
seq_puts(m, "=== ===== ================ == ===== ==========\n");
return 0;
case 3 ... 3 + SLOW_WORK_THREAD_LIMIT - 1:
id = (unsigned long) v - 3;
read_lock(&slow_work_execs_lock);
work = slow_work_execs[id];
if (work) {
smp_read_barrier_depends();
seq_printf(m, "%3lu %5d %16p %2lx ",
id, slow_work_pids[id], work, work->flags);
slow_work_print_mark(m, work);
if (work->ops->desc)
work->ops->desc(work, m);
seq_putc(m, '\n');
}
read_unlock(&slow_work_execs_lock);
return 0;
default:
work = list_entry(p, struct slow_work, link);
seq_printf(m, "%3s - %16p %2lx ",
work->flags & SLOW_WORK_VERY_SLOW ? "vsq" : "sq",
work, work->flags);
slow_work_print_mark(m, work);
if (work->ops->desc)
work->ops->desc(work, m);
seq_putc(m, '\n');
return 0;
}
}
/*
* map the iterator to a work item
*/
static void *slow_work_runqueue_index(struct seq_file *m, loff_t *_pos)
{
struct list_head *p;
unsigned long count, id;
switch (*_pos >> ITERATOR_SHIFT) {
case 0x0:
if (*_pos == 0)
*_pos = 1;
if (*_pos < 3)
return (void *)(unsigned long) *_pos;
if (*_pos < 3 + SLOW_WORK_THREAD_LIMIT)
for (id = *_pos - 3;
id < SLOW_WORK_THREAD_LIMIT;
id++, (*_pos)++)
if (slow_work_execs[id])
return (void *)(unsigned long) *_pos;
*_pos = 0x1UL << ITERATOR_SHIFT;
case 0x1:
count = *_pos & ITERATOR_COUNTER;
list_for_each(p, &slow_work_queue) {
if (count == 0)
return p;
count--;
}
*_pos = 0x2UL << ITERATOR_SHIFT;
case 0x2:
count = *_pos & ITERATOR_COUNTER;
list_for_each(p, &vslow_work_queue) {
if (count == 0)
return p;
count--;
}
*_pos = 0x3UL << ITERATOR_SHIFT;
default:
return NULL;
}
}
/*
* set up the iterator to start reading from the first line
*/
static void *slow_work_runqueue_start(struct seq_file *m, loff_t *_pos)
{
spin_lock_irq(&slow_work_queue_lock);
return slow_work_runqueue_index(m, _pos);
}
/*
* move to the next line
*/
static void *slow_work_runqueue_next(struct seq_file *m, void *v, loff_t *_pos)
{
struct list_head *p = v;
unsigned long selector = *_pos >> ITERATOR_SHIFT;
(*_pos)++;
switch (selector) {
case 0x0:
return slow_work_runqueue_index(m, _pos);
case 0x1:
if (*_pos >> ITERATOR_SHIFT == 0x1) {
p = p->next;
if (p != &slow_work_queue)
return p;
}
*_pos = 0x2UL << ITERATOR_SHIFT;
p = &vslow_work_queue;
case 0x2:
if (*_pos >> ITERATOR_SHIFT == 0x2) {
p = p->next;
if (p != &vslow_work_queue)
return p;
}
*_pos = 0x3UL << ITERATOR_SHIFT;
default:
return NULL;
}
}
/*
* clean up after reading
*/
static void slow_work_runqueue_stop(struct seq_file *m, void *v)
{
spin_unlock_irq(&slow_work_queue_lock);
}
static const struct seq_operations slow_work_runqueue_ops = {
.start = slow_work_runqueue_start,
.stop = slow_work_runqueue_stop,
.next = slow_work_runqueue_next,
.show = slow_work_runqueue_show,
};
/*
* open "/sys/kernel/debug/slow_work/runqueue" to list queue contents
*/
static int slow_work_runqueue_open(struct inode *inode, struct file *file)
{
return seq_open(file, &slow_work_runqueue_ops);
}
const struct file_operations slow_work_runqueue_fops = {
.owner = THIS_MODULE,
.open = slow_work_runqueue_open,
.read = seq_read,
.llseek = seq_lseek,
.release = seq_release,
};
kernel/slow-work.c deleted 100644 → 0
View file @ 6ecd7c2d
/* Worker thread pool for slow items, such as filesystem lookups or mkdirs
*
* Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public Licence
* as published by the Free Software Foundation; either version
* 2 of the Licence, or (at your option) any later version.
*
* See Documentation/slow-work.txt
*/
#include <linux/module.h>
#include <linux/slow-work.h>
#include <linux/kthread.h>
#include <linux/freezer.h>
#include <linux/wait.h>
#include <linux/debugfs.h>
#include "slow-work.h"
static void slow_work_cull_timeout(unsigned long);
static void slow_work_oom_timeout(unsigned long);
#ifdef CONFIG_SYSCTL
static int slow_work_min_threads_sysctl(struct ctl_table *, int,
void __user *, size_t *, loff_t *);
static int slow_work_max_threads_sysctl(struct ctl_table *, int ,
void __user *, size_t *, loff_t *);
#endif
/*
* The pool of threads has at least min threads in it as long as someone is
* using the facility, and may have as many as max.
*
* A portion of the pool may be processing very slow operations.
*/
static unsigned slow_work_min_threads = 2;
static unsigned slow_work_max_threads = 4;
static unsigned vslow_work_proportion = 50; /* % of threads that may process
* very slow work */
#ifdef CONFIG_SYSCTL
static const int slow_work_min_min_threads = 2;
static int slow_work_max_max_threads = SLOW_WORK_THREAD_LIMIT;
static const int slow_work_min_vslow = 1;
static const int slow_work_max_vslow = 99;
ctl_table slow_work_sysctls[] = {
{
.procname = "min-threads",
.data = &slow_work_min_threads,
.maxlen = sizeof(unsigned),
.mode = 0644,
.proc_handler = slow_work_min_threads_sysctl,
.extra1 = (void *) &slow_work_min_min_threads,
.extra2 = &slow_work_max_threads,
},
{
.procname = "max-threads",
.data = &slow_work_max_threads,
.maxlen = sizeof(unsigned),
.mode = 0644,
.proc_handler = slow_work_max_threads_sysctl,
.extra1 = &slow_work_min_threads,
.extra2 = (void *) &slow_work_max_max_threads,
},
{
.procname = "vslow-percentage",
.data = &vslow_work_proportion,
.maxlen = sizeof(unsigned),
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
.extra1 = (void *) &slow_work_min_vslow,
.extra2 = (void *) &slow_work_max_vslow,
},
{}
};
#endif
/*
* The active state of the thread pool
*/
static atomic_t slow_work_thread_count;
static atomic_t vslow_work_executing_count;
static bool slow_work_may_not_start_new_thread;
static bool slow_work_cull; /* cull a thread due to lack of activity */
static DEFINE_TIMER(slow_work_cull_timer, slow_work_cull_timeout, 0, 0);
static DEFINE_TIMER(slow_work_oom_timer, slow_work_oom_timeout, 0, 0);
static struct slow_work slow_work_new_thread; /* new thread starter */
/*
* slow work ID allocation (use slow_work_queue_lock)
*/
static DECLARE_BITMAP(slow_work_ids, SLOW_WORK_THREAD_LIMIT);
/*
* Unregistration tracking to prevent put_ref() from disappearing during module
* unload
*/
#ifdef CONFIG_MODULES
static struct module *slow_work_thread_processing[SLOW_WORK_THREAD_LIMIT];
static struct module *slow_work_unreg_module;
static struct slow_work *slow_work_unreg_work_item;
static DECLARE_WAIT_QUEUE_HEAD(slow_work_unreg_wq);
static DEFINE_MUTEX(slow_work_unreg_sync_lock);
static void slow_work_set_thread_processing(int id, struct slow_work *work)
{
if (work)
slow_work_thread_processing[id] = work->owner;
}
static void slow_work_done_thread_processing(int id, struct slow_work *work)
{
struct module *module = slow_work_thread_processing[id];
slow_work_thread_processing[id] = NULL;
smp_mb();
if (slow_work_unreg_work_item == work ||
slow_work_unreg_module == module)
wake_up_all(&slow_work_unreg_wq);
}
static void slow_work_clear_thread_processing(int id)
{
slow_work_thread_processing[id] = NULL;
}
#else
static void slow_work_set_thread_processing(int id, struct slow_work *work) {}
static void slow_work_done_thread_processing(int id, struct slow_work *work) {}
static void slow_work_clear_thread_processing(int id) {}
#endif
/*
* Data for tracking currently executing items for indication through /proc
*/
#ifdef CONFIG_SLOW_WORK_DEBUG
struct slow_work *slow_work_execs[SLOW_WORK_THREAD_LIMIT];
pid_t slow_work_pids[SLOW_WORK_THREAD_LIMIT];
DEFINE_RWLOCK(slow_work_execs_lock);
#endif
/*
* The queues of work items and the lock governing access to them. These are
* shared between all the CPUs. It doesn't make sense to have per-CPU queues
* as the number of threads bears no relation to the number of CPUs.
*
* There are two queues of work items: one for slow work items, and one for
* very slow work items.
*/
LIST_HEAD(slow_work_queue);
LIST_HEAD(vslow_work_queue);
DEFINE_SPINLOCK(slow_work_queue_lock);
/*
* The following are two wait queues that get pinged when a work item is placed
* on an empty queue. These allow work items that are hogging a thread by
* sleeping in a way that could be deferred to yield their thread and enqueue
* themselves.
*/
static DECLARE_WAIT_QUEUE_HEAD(slow_work_queue_waits_for_occupation);
static DECLARE_WAIT_QUEUE_HEAD(vslow_work_queue_waits_for_occupation);
/*
* The thread controls. A variable used to signal to the threads that they
* should exit when the queue is empty, a waitqueue used by the threads to wait
* for signals, and a completion set by the last thread to exit.
*/
static bool slow_work_threads_should_exit;
static DECLARE_WAIT_QUEUE_HEAD(slow_work_thread_wq);
static DECLARE_COMPLETION(slow_work_last_thread_exited);
/*
* The number of users of the thread pool and its lock. Whilst this is zero we
* have no threads hanging around, and when this reaches zero, we wait for all
* active or queued work items to complete and kill all the threads we do have.
*/
static int slow_work_user_count;
static DEFINE_MUTEX(slow_work_user_lock);
static inline int slow_work_get_ref(struct slow_work *work)
{
if (work->ops->get_ref)
return work->ops->get_ref(work);
return 0;
}
static inline void slow_work_put_ref(struct slow_work *work)
{
if (work->ops->put_ref)
work->ops->put_ref(work);
}
/*
* Calculate the maximum number of active threads in the pool that are
* permitted to process very slow work items.
*
* The answer is rounded up to at least 1, but may not equal or exceed the
* maximum number of the threads in the pool. This means we always have at
* least one thread that can process slow work items, and we always have at
* least one thread that won't get tied up doing so.
*/
static unsigned slow_work_calc_vsmax(void)
{
unsigned vsmax;
vsmax = atomic_read(&slow_work_thread_count) * vslow_work_proportion;
vsmax /= 100;
vsmax = max(vsmax, 1U);
return min(vsmax, slow_work_max_threads - 1);
}
/*
* Attempt to execute stuff queued on a slow thread. Return true if we managed
* it, false if there was nothing to do.
*/
static noinline bool slow_work_execute(int id)
{
struct slow_work *work = NULL;
unsigned vsmax;
bool very_slow;
vsmax = slow_work_calc_vsmax();
/* see if we can schedule a new thread to be started if we're not
* keeping up with the work */
if (!waitqueue_active(&slow_work_thread_wq) &&
(!list_empty(&slow_work_queue) || !list_empty(&vslow_work_queue)) &&
atomic_read(&slow_work_thread_count) < slow_work_max_threads &&
!slow_work_may_not_start_new_thread)
slow_work_enqueue(&slow_work_new_thread);
/* find something to execute */
spin_lock_irq(&slow_work_queue_lock);
if (!list_empty(&vslow_work_queue) &&
atomic_read(&vslow_work_executing_count) < vsmax) {
work = list_entry(vslow_work_queue.next,
struct slow_work, link);
if (test_and_set_bit_lock(SLOW_WORK_EXECUTING, &work->flags))
BUG();
list_del_init(&work->link);
atomic_inc(&vslow_work_executing_count);
very_slow = true;
} else if (!list_empty(&slow_work_queue)) {
work = list_entry(slow_work_queue.next,
struct slow_work, link);
if (test_and_set_bit_lock(SLOW_WORK_EXECUTING, &work->flags))
BUG();
list_del_init(&work->link);
very_slow = false;
} else {
very_slow = false; /* avoid the compiler warning */
}
slow_work_set_thread_processing(id, work);
if (work) {
slow_work_mark_time(work);
slow_work_begin_exec(id, work);
}
spin_unlock_irq(&slow_work_queue_lock);
if (!work)
return false;
if (!test_and_clear_bit(SLOW_WORK_PENDING, &work->flags))
BUG();
/* don't execute if the work is in the process of being cancelled */
if (!test_bit(SLOW_WORK_CANCELLING, &work->flags))
work->ops->execute(work);
if (very_slow)
atomic_dec(&vslow_work_executing_count);
clear_bit_unlock(SLOW_WORK_EXECUTING, &work->flags);
/* wake up anyone waiting for this work to be complete */
wake_up_bit(&work->flags, SLOW_WORK_EXECUTING);
slow_work_end_exec(id, work);
/* if someone tried to enqueue the item whilst we were executing it,
* then it'll be left unenqueued to avoid multiple threads trying to
* execute it simultaneously
*
* there is, however, a race between us testing the pending flag and
* getting the spinlock, and between the enqueuer setting the pending
* flag and getting the spinlock, so we use a deferral bit to tell us
* if the enqueuer got there first
*/
if (test_bit(SLOW_WORK_PENDING, &work->flags)) {
spin_lock_irq(&slow_work_queue_lock);
if (!test_bit(SLOW_WORK_EXECUTING, &work->flags) &&
test_and_clear_bit(SLOW_WORK_ENQ_DEFERRED, &work->flags))
goto auto_requeue;
spin_unlock_irq(&slow_work_queue_lock);
}
/* sort out the race between module unloading and put_ref() */
slow_work_put_ref(work);
slow_work_done_thread_processing(id, work);
return true;
auto_requeue:
/* we must complete the enqueue operation
* - we transfer our ref on the item back to the appropriate queue
* - don't wake another thread up as we're awake already
*/
slow_work_mark_time(work);
if (test_bit(SLOW_WORK_VERY_SLOW, &work->flags))
list_add_tail(&work->link, &vslow_work_queue);
else
list_add_tail(&work->link, &slow_work_queue);
spin_unlock_irq(&slow_work_queue_lock);
slow_work_clear_thread_processing(id);
return true;
}
/**
* slow_work_sleep_till_thread_needed - Sleep till thread needed by other work
* work: The work item under execution that wants to sleep
* _timeout: Scheduler sleep timeout
*
* Allow a requeueable work item to sleep on a slow-work processor thread until
* that thread is needed to do some other work or the sleep is interrupted by
* some other event.
*
* The caller must set up a wake up event before calling this and must have set
* the appropriate sleep mode (such as TASK_UNINTERRUPTIBLE) and tested its own
* condition before calling this function as no test is made here.
*
* False is returned if there is nothing on the queue; true is returned if the
* work item should be requeued
*/
bool slow_work_sleep_till_thread_needed(struct slow_work *work,
signed long *_timeout)
{
wait_queue_head_t *wfo_wq;
struct list_head *queue;
DEFINE_WAIT(wait);
if (test_bit(SLOW_WORK_VERY_SLOW, &work->flags)) {
wfo_wq = &vslow_work_queue_waits_for_occupation;
queue = &vslow_work_queue;
} else {
wfo_wq = &slow_work_queue_waits_for_occupation;
queue = &slow_work_queue;
}
if (!list_empty(queue))
return true;
add_wait_queue_exclusive(wfo_wq, &wait);
if (list_empty(queue))
*_timeout = schedule_timeout(*_timeout);
finish_wait(wfo_wq, &wait);
return !list_empty(queue);
}
EXPORT_SYMBOL(slow_work_sleep_till_thread_needed);
/**
* slow_work_enqueue - Schedule a slow work item for processing
* @work: The work item to queue
*
* Schedule a slow work item for processing. If the item is already undergoing
* execution, this guarantees not to re-enter the execution routine until the
* first execution finishes.
*
* The item is pinned by this function as it retains a reference to it, managed
* through the item operations. The item is unpinned once it has been
* executed.
*
* An item may hog the thread that is running it for a relatively large amount
* of time, sufficient, for example, to perform several lookup, mkdir, create
* and setxattr operations. It may sleep on I/O and may sleep to obtain locks.
*
* Conversely, if a number of items are awaiting processing, it may take some
* time before any given item is given attention. The number of threads in the
* pool may be increased to deal with demand, but only up to a limit.
*
* If SLOW_WORK_VERY_SLOW is set on the work item, then it will be placed in
* the very slow queue, from which only a portion of the threads will be
* allowed to pick items to execute. This ensures that very slow items won't
* overly block ones that are just ordinarily slow.
*
* Returns 0 if successful, -EAGAIN if not (or -ECANCELED if cancelled work is
* attempted queued)
*/
int slow_work_enqueue(struct slow_work *work)
{
wait_queue_head_t *wfo_wq;
struct list_head *queue;
unsigned long flags;
int ret;
if (test_bit(SLOW_WORK_CANCELLING, &work->flags))
return -ECANCELED;
BUG_ON(slow_work_user_count <= 0);
BUG_ON(!work);
BUG_ON(!work->ops);
/* when honouring an enqueue request, we only promise that we will run
* the work function in the future; we do not promise to run it once
* per enqueue request
*
* we use the PENDING bit to merge together repeat requests without
* having to disable IRQs and take the spinlock, whilst still
* maintaining our promise
*/
if (!test_and_set_bit_lock(SLOW_WORK_PENDING, &work->flags)) {
if (test_bit(SLOW_WORK_VERY_SLOW, &work->flags)) {
wfo_wq = &vslow_work_queue_waits_for_occupation;
queue = &vslow_work_queue;
} else {
wfo_wq = &slow_work_queue_waits_for_occupation;
queue = &slow_work_queue;
}
spin_lock_irqsave(&slow_work_queue_lock, flags);
if (unlikely(test_bit(SLOW_WORK_CANCELLING, &work->flags)))
goto cancelled;
/* we promise that we will not attempt to execute the work
* function in more than one thread simultaneously
*
* this, however, leaves us with a problem if we're asked to
* enqueue the work whilst someone is executing the work
* function as simply queueing the work immediately means that
* another thread may try executing it whilst it is already
* under execution
*
* to deal with this, we set the ENQ_DEFERRED bit instead of
* enqueueing, and the thread currently executing the work
* function will enqueue the work item when the work function
* returns and it has cleared the EXECUTING bit
*/
if (test_bit(SLOW_WORK_EXECUTING, &work->flags)) {
set_bit(SLOW_WORK_ENQ_DEFERRED, &work->flags);
} else {
ret = slow_work_get_ref(work);
if (ret < 0)
goto failed;
slow_work_mark_time(work);
list_add_tail(&work->link, queue);
wake_up(&slow_work_thread_wq);
/* if someone who could be requeued is sleeping on a
* thread, then ask them to yield their thread */
if (work->link.prev == queue)
wake_up(wfo_wq);
}
spin_unlock_irqrestore(&slow_work_queue_lock, flags);
}
return 0;
cancelled:
ret = -ECANCELED;
failed:
spin_unlock_irqrestore(&slow_work_queue_lock, flags);
return ret;
}
EXPORT_SYMBOL(slow_work_enqueue);
static int slow_work_wait(void *word)
{
schedule();
return 0;
}
/**
* slow_work_cancel - Cancel a slow work item
* @work: The work item to cancel
*
* This function will cancel a previously enqueued work item. If we cannot
* cancel the work item, it is guarenteed to have run when this function
* returns.
*/
void slow_work_cancel(struct slow_work *work)
{
bool wait = true, put = false;
set_bit(SLOW_WORK_CANCELLING, &work->flags);
smp_mb();
/* if the work item is a delayed work item with an active timer, we
* need to wait for the timer to finish _before_ getting the spinlock,
* lest we deadlock against the timer routine
*
* the timer routine will leave DELAYED set if it notices the
* CANCELLING flag in time
*/
if (test_bit(SLOW_WORK_DELAYED, &work->flags)) {
struct delayed_slow_work *dwork =
container_of(work, struct delayed_slow_work, work);
del_timer_sync(&dwork->timer);
}
spin_lock_irq(&slow_work_queue_lock);
if (test_bit(SLOW_WORK_DELAYED, &work->flags)) {
/* the timer routine aborted or never happened, so we are left
* holding the timer's reference on the item and should just
* drop the pending flag and wait for any ongoing execution to
* finish */
struct delayed_slow_work *dwork =
container_of(work, struct delayed_slow_work, work);
BUG_ON(timer_pending(&dwork->timer));
BUG_ON(!list_empty(&work->link));
clear_bit(SLOW_WORK_DELAYED, &work->flags);
put = true;
clear_bit(SLOW_WORK_PENDING, &work->flags);
} else if (test_bit(SLOW_WORK_PENDING, &work->flags) &&
!list_empty(&work->link)) {
/* the link in the pending queue holds a reference on the item
* that we will need to release */
list_del_init(&work->link);
wait = false;
put = true;
clear_bit(SLOW_WORK_PENDING, &work->flags);
} else if (test_and_clear_bit(SLOW_WORK_ENQ_DEFERRED, &work->flags)) {
/* the executor is holding our only reference on the item, so
* we merely need to wait for it to finish executing */
clear_bit(SLOW_WORK_PENDING, &work->flags);
}
spin_unlock_irq(&slow_work_queue_lock);
/* the EXECUTING flag is set by the executor whilst the spinlock is set
* and before the item is dequeued - so assuming the above doesn't
* actually dequeue it, simply waiting for the EXECUTING flag to be
* released here should be sufficient */
if (wait)
wait_on_bit(&work->flags, SLOW_WORK_EXECUTING, slow_work_wait,
TASK_UNINTERRUPTIBLE);
clear_bit(SLOW_WORK_CANCELLING, &work->flags);
if (put)
slow_work_put_ref(work);
}
EXPORT_SYMBOL(slow_work_cancel);
/*
* Handle expiry of the delay timer, indicating that a delayed slow work item
* should now be queued if not cancelled
*/
static void delayed_slow_work_timer(unsigned long data)
{
wait_queue_head_t *wfo_wq;
struct list_head *queue;
struct slow_work *work = (struct slow_work *) data;
unsigned long flags;
bool queued = false, put = false, first = false;
if (test_bit(SLOW_WORK_VERY_SLOW, &work->flags)) {
wfo_wq = &vslow_work_queue_waits_for_occupation;
queue = &vslow_work_queue;
} else {
wfo_wq = &slow_work_queue_waits_for_occupation;
queue = &slow_work_queue;
}
spin_lock_irqsave(&slow_work_queue_lock, flags);
if (likely(!test_bit(SLOW_WORK_CANCELLING, &work->flags))) {
clear_bit(SLOW_WORK_DELAYED, &work->flags);
if (test_bit(SLOW_WORK_EXECUTING, &work->flags)) {
/* we discard the reference the timer was holding in
* favour of the one the executor holds */
set_bit(SLOW_WORK_ENQ_DEFERRED, &work->flags);
put = true;
} else {
slow_work_mark_time(work);
list_add_tail(&work->link, queue);
queued = true;
if (work->link.prev == queue)
first = true;
}
}
spin_unlock_irqrestore(&slow_work_queue_lock, flags);
if (put)
slow_work_put_ref(work);
if (first)
wake_up(wfo_wq);
if (queued)
wake_up(&slow_work_thread_wq);
}
/**
* delayed_slow_work_enqueue - Schedule a delayed slow work item for processing
* @dwork: The delayed work item to queue
* @delay: When to start executing the work, in jiffies from now
*
* This is similar to slow_work_enqueue(), but it adds a delay before the work
* is actually queued for processing.
*
* The item can have delayed processing requested on it whilst it is being
* executed. The delay will begin immediately, and if it expires before the
* item finishes executing, the item will be placed back on the queue when it
* has done executing.
*/
int delayed_slow_work_enqueue(struct delayed_slow_work *dwork,
unsigned long delay)
{
struct slow_work *work = &dwork->work;
unsigned long flags;
int ret;
if (delay == 0)
return slow_work_enqueue(&dwork->work);
BUG_ON(slow_work_user_count <= 0);
BUG_ON(!work);
BUG_ON(!work->ops);
if (test_bit(SLOW_WORK_CANCELLING, &work->flags))
return -ECANCELED;
if (!test_and_set_bit_lock(SLOW_WORK_PENDING, &work->flags)) {
spin_lock_irqsave(&slow_work_queue_lock, flags);
if (test_bit(SLOW_WORK_CANCELLING, &work->flags))
goto cancelled;
/* the timer holds a reference whilst it is pending */
ret = slow_work_get_ref(work);
if (ret < 0)
goto cant_get_ref;
if (test_and_set_bit(SLOW_WORK_DELAYED, &work->flags))
BUG();
dwork->timer.expires = jiffies + delay;
dwork->timer.data = (unsigned long) work;
dwork->timer.function = delayed_slow_work_timer;
add_timer(&dwork->timer);
spin_unlock_irqrestore(&slow_work_queue_lock, flags);
}
return 0;
cancelled:
ret = -ECANCELED;
cant_get_ref:
spin_unlock_irqrestore(&slow_work_queue_lock, flags);
return ret;
}
EXPORT_SYMBOL(delayed_slow_work_enqueue);
/*
* Schedule a cull of the thread pool at some time in the near future
*/
static void slow_work_schedule_cull(void)
{
mod_timer(&slow_work_cull_timer,
round_jiffies(jiffies + SLOW_WORK_CULL_TIMEOUT));
}
/*
* Worker thread culling algorithm
*/
static bool slow_work_cull_thread(void)
{
unsigned long flags;
bool do_cull = false;
spin_lock_irqsave(&slow_work_queue_lock, flags);
if (slow_work_cull) {
slow_work_cull = false;
if (list_empty(&slow_work_queue) &&
list_empty(&vslow_work_queue) &&
atomic_read(&slow_work_thread_count) >
slow_work_min_threads) {
slow_work_schedule_cull();
do_cull = true;
}
}
spin_unlock_irqrestore(&slow_work_queue_lock, flags);
return do_cull;
}
/*
* Determine if there is slow work available for dispatch
*/
static inline bool slow_work_available(int vsmax)
{
return !list_empty(&slow_work_queue) ||
(!list_empty(&vslow_work_queue) &&
atomic_read(&vslow_work_executing_count) < vsmax);
}
/*
* Worker thread dispatcher
*/
static int slow_work_thread(void *_data)
{
int vsmax, id;
DEFINE_WAIT(wait);
set_freezable();
set_user_nice(current, -5);
/* allocate ourselves an ID */
spin_lock_irq(&slow_work_queue_lock);
id = find_first_zero_bit(slow_work_ids, SLOW_WORK_THREAD_LIMIT);
BUG_ON(id < 0 || id >= SLOW_WORK_THREAD_LIMIT);
__set_bit(id, slow_work_ids);
slow_work_set_thread_pid(id, current->pid);
spin_unlock_irq(&slow_work_queue_lock);
sprintf(current->comm, "kslowd%03u", id);
for (;;) {
vsmax = vslow_work_proportion;
vsmax *= atomic_read(&slow_work_thread_count);
vsmax /= 100;
prepare_to_wait_exclusive(&slow_work_thread_wq, &wait,
TASK_INTERRUPTIBLE);
if (!freezing(current) &&
!slow_work_threads_should_exit &&
!slow_work_available(vsmax) &&
!slow_work_cull)
schedule();
finish_wait(&slow_work_thread_wq, &wait);
try_to_freeze();
vsmax = vslow_work_proportion;
vsmax *= atomic_read(&slow_work_thread_count);
vsmax /= 100;
if (slow_work_available(vsmax) && slow_work_execute(id)) {
cond_resched();
if (list_empty(&slow_work_queue) &&
list_empty(&vslow_work_queue) &&
atomic_read(&slow_work_thread_count) >
slow_work_min_threads)
slow_work_schedule_cull();
continue;
}
if (slow_work_threads_should_exit)
break;
if (slow_work_cull && slow_work_cull_thread())
break;
}
spin_lock_irq(&slow_work_queue_lock);
slow_work_set_thread_pid(id, 0);
__clear_bit(id, slow_work_ids);
spin_unlock_irq(&slow_work_queue_lock);
if (atomic_dec_and_test(&slow_work_thread_count))
complete_and_exit(&slow_work_last_thread_exited, 0);
return 0;
}
/*
* Handle thread cull timer expiration
*/
static void slow_work_cull_timeout(unsigned long data)
{
slow_work_cull = true;
wake_up(&slow_work_thread_wq);
}
/*
* Start a new slow work thread
*/
static void slow_work_new_thread_execute(struct slow_work *work)
{
struct task_struct *p;
if (slow_work_threads_should_exit)
return;
if (atomic_read(&slow_work_thread_count) >= slow_work_max_threads)
return;
if (!mutex_trylock(&slow_work_user_lock))
return;
slow_work_may_not_start_new_thread = true;
atomic_inc(&slow_work_thread_count);
p = kthread_run(slow_work_thread, NULL, "kslowd");
if (IS_ERR(p)) {
printk(KERN_DEBUG "Slow work thread pool: OOM\n");
if (atomic_dec_and_test(&slow_work_thread_count))
BUG(); /* we're running on a slow work thread... */
mod_timer(&slow_work_oom_timer,
round_jiffies(jiffies + SLOW_WORK_OOM_TIMEOUT));
} else {
/* ratelimit the starting of new threads */
mod_timer(&slow_work_oom_timer, jiffies + 1);
}
mutex_unlock(&slow_work_user_lock);
}
static const struct slow_work_ops slow_work_new_thread_ops = {
.owner = THIS_MODULE,
.execute = slow_work_new_thread_execute,
#ifdef CONFIG_SLOW_WORK_DEBUG
.desc = slow_work_new_thread_desc,
#endif
};
/*
* post-OOM new thread start suppression expiration
*/
static void slow_work_oom_timeout(unsigned long data)
{
slow_work_may_not_start_new_thread = false;
}
#ifdef CONFIG_SYSCTL
/*
* Handle adjustment of the minimum number of threads
*/
static int slow_work_min_threads_sysctl(struct ctl_table *table, int write,
void __user *buffer,
size_t *lenp, loff_t *ppos)
{
int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
int n;
if (ret == 0) {
mutex_lock(&slow_work_user_lock);
if (slow_work_user_count > 0) {
/* see if we need to start or stop threads */
n = atomic_read(&slow_work_thread_count) -
slow_work_min_threads;
if (n < 0 && !slow_work_may_not_start_new_thread)
slow_work_enqueue(&slow_work_new_thread);
else if (n > 0)
slow_work_schedule_cull();
}
mutex_unlock(&slow_work_user_lock);
}
return ret;
}
/*
* Handle adjustment of the maximum number of threads
*/
static int slow_work_max_threads_sysctl(struct ctl_table *table, int write,
void __user *buffer,
size_t *lenp, loff_t *ppos)
{
int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
int n;
if (ret == 0) {
mutex_lock(&slow_work_user_lock);
if (slow_work_user_count > 0) {
/* see if we need to stop threads */
n = slow_work_max_threads -
atomic_read(&slow_work_thread_count);
if (n < 0)
slow_work_schedule_cull();
}
mutex_unlock(&slow_work_user_lock);
}
return ret;
}
#endif /* CONFIG_SYSCTL */
/**
* slow_work_register_user - Register a user of the facility
* @module: The module about to make use of the facility
*
* Register a user of the facility, starting up the initial threads if there
* aren't any other users at this point. This will return 0 if successful, or
* an error if not.
*/
int slow_work_register_user(struct module *module)
{
struct task_struct *p;
int loop;
mutex_lock(&slow_work_user_lock);
if (slow_work_user_count == 0) {
printk(KERN_NOTICE "Slow work thread pool: Starting up\n");
init_completion(&slow_work_last_thread_exited);
slow_work_threads_should_exit = false;
slow_work_init(&slow_work_new_thread,
&slow_work_new_thread_ops);
slow_work_may_not_start_new_thread = false;
slow_work_cull = false;
/* start the minimum number of threads */
for (loop = 0; loop < slow_work_min_threads; loop++) {
atomic_inc(&slow_work_thread_count);
p = kthread_run(slow_work_thread, NULL, "kslowd");
if (IS_ERR(p))
goto error;
}
printk(KERN_NOTICE "Slow work thread pool: Ready\n");
}
slow_work_user_count++;
mutex_unlock(&slow_work_user_lock);
return 0;
error:
if (atomic_dec_and_test(&slow_work_thread_count))
complete(&slow_work_last_thread_exited);
if (loop > 0) {
printk(KERN_ERR "Slow work thread pool:"
" Aborting startup on ENOMEM\n");
slow_work_threads_should_exit = true;
wake_up_all(&slow_work_thread_wq);
wait_for_completion(&slow_work_last_thread_exited);
printk(KERN_ERR "Slow work thread pool: Aborted\n");
}
mutex_unlock(&slow_work_user_lock);
return PTR_ERR(p);
}
EXPORT_SYMBOL(slow_work_register_user);
/*
* wait for all outstanding items from the calling module to complete
* - note that more items may be queued whilst we're waiting
*/
static void slow_work_wait_for_items(struct module *module)
{
#ifdef CONFIG_MODULES
DECLARE_WAITQUEUE(myself, current);
struct slow_work *work;
int loop;
mutex_lock(&slow_work_unreg_sync_lock);
add_wait_queue(&slow_work_unreg_wq, &myself);
for (;;) {
spin_lock_irq(&slow_work_queue_lock);
/* first of all, we wait for the last queued item in each list
* to be processed */
list_for_each_entry_reverse(work, &vslow_work_queue, link) {
if (work->owner == module) {
set_current_state(TASK_UNINTERRUPTIBLE);
slow_work_unreg_work_item = work;
goto do_wait;
}
}
list_for_each_entry_reverse(work, &slow_work_queue, link) {
if (work->owner == module) {
set_current_state(TASK_UNINTERRUPTIBLE);
slow_work_unreg_work_item = work;
goto do_wait;
}
}
/* then we wait for the items being processed to finish */
slow_work_unreg_module = module;
smp_mb();
for (loop = 0; loop < SLOW_WORK_THREAD_LIMIT; loop++) {
if (slow_work_thread_processing[loop] == module)
goto do_wait;
}
spin_unlock_irq(&slow_work_queue_lock);
break; /* okay, we're done */
do_wait:
spin_unlock_irq(&slow_work_queue_lock);
schedule();
slow_work_unreg_work_item = NULL;
slow_work_unreg_module = NULL;
}
remove_wait_queue(&slow_work_unreg_wq, &myself);
mutex_unlock(&slow_work_unreg_sync_lock);
#endif /* CONFIG_MODULES */
}
/**
* slow_work_unregister_user - Unregister a user of the facility
* @module: The module whose items should be cleared
*
* Unregister a user of the facility, killing all the threads if this was the
* last one.
*
* This waits for all the work items belonging to the nominated module to go
* away before proceeding.
*/
void slow_work_unregister_user(struct module *module)
{
/* first of all, wait for all outstanding items from the calling module
* to complete */
if (module)
slow_work_wait_for_items(module);
/* then we can actually go about shutting down the facility if need
* be */
mutex_lock(&slow_work_user_lock);
BUG_ON(slow_work_user_count <= 0);
slow_work_user_count--;
if (slow_work_user_count == 0) {
printk(KERN_NOTICE "Slow work thread pool: Shutting down\n");
slow_work_threads_should_exit = true;
del_timer_sync(&slow_work_cull_timer);
del_timer_sync(&slow_work_oom_timer);
wake_up_all(&slow_work_thread_wq);
wait_for_completion(&slow_work_last_thread_exited);
printk(KERN_NOTICE "Slow work thread pool:"
" Shut down complete\n");
}
mutex_unlock(&slow_work_user_lock);
}
EXPORT_SYMBOL(slow_work_unregister_user);
/*
* Initialise the slow work facility
*/
static int __init init_slow_work(void)
{
unsigned nr_cpus = num_possible_cpus();
if (slow_work_max_threads < nr_cpus)
slow_work_max_threads = nr_cpus;
#ifdef CONFIG_SYSCTL
if (slow_work_max_max_threads < nr_cpus * 2)
slow_work_max_max_threads = nr_cpus * 2;
#endif
#ifdef CONFIG_SLOW_WORK_DEBUG
{
struct dentry *dbdir;
dbdir = debugfs_create_dir("slow_work", NULL);
if (dbdir && !IS_ERR(dbdir))
debugfs_create_file("runqueue", S_IFREG | 0400, dbdir,
NULL, &slow_work_runqueue_fops);
}
#endif
return 0;
}
subsys_initcall(init_slow_work);
kernel/slow-work.h deleted 100644 → 0
View file @ 6ecd7c2d
/* Slow work private definitions
*
* Copyright (C) 2009 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public Licence
* as published by the Free Software Foundation; either version
* 2 of the Licence, or (at your option) any later version.
*/
#define SLOW_WORK_CULL_TIMEOUT (5 * HZ) /* cull threads 5s after running out of
* things to do */
#define SLOW_WORK_OOM_TIMEOUT (5 * HZ) /* can't start new threads for 5s after
* OOM */
#define SLOW_WORK_THREAD_LIMIT 255 /* abs maximum number of slow-work threads */
/*
* slow-work.c
*/
#ifdef CONFIG_SLOW_WORK_DEBUG
extern struct slow_work *slow_work_execs[];
extern pid_t slow_work_pids[];
extern rwlock_t slow_work_execs_lock;
#endif
extern struct list_head slow_work_queue;
extern struct list_head vslow_work_queue;
extern spinlock_t slow_work_queue_lock;
/*
* slow-work-debugfs.c
*/
#ifdef CONFIG_SLOW_WORK_DEBUG
extern const struct file_operations slow_work_runqueue_fops;
extern void slow_work_new_thread_desc(struct slow_work *, struct seq_file *);
#endif
/*
* Helper functions
*/
static inline void slow_work_set_thread_pid(int id, pid_t pid)
{
#ifdef CONFIG_SLOW_WORK_DEBUG
slow_work_pids[id] = pid;
#endif
}
static inline void slow_work_mark_time(struct slow_work *work)
{
#ifdef CONFIG_SLOW_WORK_DEBUG
work->mark = CURRENT_TIME;
#endif
}
static inline void slow_work_begin_exec(int id, struct slow_work *work)
{
#ifdef CONFIG_SLOW_WORK_DEBUG
slow_work_execs[id] = work;
#endif
}
static inline void slow_work_end_exec(int id, struct slow_work *work)
{
#ifdef CONFIG_SLOW_WORK_DEBUG
write_lock(&slow_work_execs_lock);
slow_work_execs[id] = NULL;
write_unlock(&slow_work_execs_lock);
#endif
}
kernel/sysctl.c
View file @ 181a51f6
......@@ -50,7 +50,6 @@
#include <linux/acpi.h>
#include <linux/reboot.h>
#include <linux/ftrace.h>
#include <linux/slow-work.h>
#include <linux/perf_event.h>
#include <linux/kprobes.h>
#include <linux/pipe_fs_i.h>
......@@ -906,13 +905,6 @@ static struct ctl_table kern_table[] = {
.proc_handler = proc_dointvec,
},
#endif
#ifdef CONFIG_SLOW_WORK
{
.procname = "slow-work",
.mode = 0555,
.child = slow_work_sysctls,
},
#endif
#ifdef CONFIG_PERF_EVENTS
{
.procname = "perf_event_paranoid",
......
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