![David Howells](/assets/img/avatar_default.png)
Move slow_work's debugging proc file to debugfs. Signed-off-by: David Howells <dhowells@redhat.com> Requested-and-acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1072 lines
30 KiB
C
1072 lines
30 KiB
C
/* Worker thread pool for slow items, such as filesystem lookups or mkdirs
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*
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* Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public Licence
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* as published by the Free Software Foundation; either version
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* 2 of the Licence, or (at your option) any later version.
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*
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* See Documentation/slow-work.txt
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*/
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#include <linux/module.h>
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#include <linux/slow-work.h>
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#include <linux/kthread.h>
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#include <linux/freezer.h>
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#include <linux/wait.h>
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#include <linux/debugfs.h>
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#include "slow-work.h"
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static void slow_work_cull_timeout(unsigned long);
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static void slow_work_oom_timeout(unsigned long);
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#ifdef CONFIG_SYSCTL
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static int slow_work_min_threads_sysctl(struct ctl_table *, int,
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void __user *, size_t *, loff_t *);
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static int slow_work_max_threads_sysctl(struct ctl_table *, int ,
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void __user *, size_t *, loff_t *);
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#endif
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/*
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* The pool of threads has at least min threads in it as long as someone is
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* using the facility, and may have as many as max.
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*
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* A portion of the pool may be processing very slow operations.
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*/
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static unsigned slow_work_min_threads = 2;
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static unsigned slow_work_max_threads = 4;
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static unsigned vslow_work_proportion = 50; /* % of threads that may process
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* very slow work */
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#ifdef CONFIG_SYSCTL
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static const int slow_work_min_min_threads = 2;
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static int slow_work_max_max_threads = SLOW_WORK_THREAD_LIMIT;
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static const int slow_work_min_vslow = 1;
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static const int slow_work_max_vslow = 99;
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ctl_table slow_work_sysctls[] = {
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{
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.ctl_name = CTL_UNNUMBERED,
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.procname = "min-threads",
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.data = &slow_work_min_threads,
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.maxlen = sizeof(unsigned),
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.mode = 0644,
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.proc_handler = slow_work_min_threads_sysctl,
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.extra1 = (void *) &slow_work_min_min_threads,
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.extra2 = &slow_work_max_threads,
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},
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{
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.ctl_name = CTL_UNNUMBERED,
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.procname = "max-threads",
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.data = &slow_work_max_threads,
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.maxlen = sizeof(unsigned),
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.mode = 0644,
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.proc_handler = slow_work_max_threads_sysctl,
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.extra1 = &slow_work_min_threads,
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.extra2 = (void *) &slow_work_max_max_threads,
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},
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{
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.ctl_name = CTL_UNNUMBERED,
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.procname = "vslow-percentage",
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.data = &vslow_work_proportion,
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.maxlen = sizeof(unsigned),
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.mode = 0644,
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.proc_handler = &proc_dointvec_minmax,
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.extra1 = (void *) &slow_work_min_vslow,
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.extra2 = (void *) &slow_work_max_vslow,
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},
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{ .ctl_name = 0 }
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};
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#endif
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/*
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* The active state of the thread pool
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*/
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static atomic_t slow_work_thread_count;
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static atomic_t vslow_work_executing_count;
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static bool slow_work_may_not_start_new_thread;
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static bool slow_work_cull; /* cull a thread due to lack of activity */
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static DEFINE_TIMER(slow_work_cull_timer, slow_work_cull_timeout, 0, 0);
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static DEFINE_TIMER(slow_work_oom_timer, slow_work_oom_timeout, 0, 0);
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static struct slow_work slow_work_new_thread; /* new thread starter */
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/*
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* slow work ID allocation (use slow_work_queue_lock)
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*/
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static DECLARE_BITMAP(slow_work_ids, SLOW_WORK_THREAD_LIMIT);
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/*
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* Unregistration tracking to prevent put_ref() from disappearing during module
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* unload
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*/
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#ifdef CONFIG_MODULES
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static struct module *slow_work_thread_processing[SLOW_WORK_THREAD_LIMIT];
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static struct module *slow_work_unreg_module;
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static struct slow_work *slow_work_unreg_work_item;
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static DECLARE_WAIT_QUEUE_HEAD(slow_work_unreg_wq);
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static DEFINE_MUTEX(slow_work_unreg_sync_lock);
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static void slow_work_set_thread_processing(int id, struct slow_work *work)
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{
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if (work)
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slow_work_thread_processing[id] = work->owner;
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}
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static void slow_work_done_thread_processing(int id, struct slow_work *work)
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{
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struct module *module = slow_work_thread_processing[id];
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slow_work_thread_processing[id] = NULL;
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smp_mb();
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if (slow_work_unreg_work_item == work ||
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slow_work_unreg_module == module)
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wake_up_all(&slow_work_unreg_wq);
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}
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static void slow_work_clear_thread_processing(int id)
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{
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slow_work_thread_processing[id] = NULL;
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}
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#else
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static void slow_work_set_thread_processing(int id, struct slow_work *work) {}
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static void slow_work_done_thread_processing(int id, struct slow_work *work) {}
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static void slow_work_clear_thread_processing(int id) {}
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#endif
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/*
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* Data for tracking currently executing items for indication through /proc
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*/
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#ifdef CONFIG_SLOW_WORK_DEBUG
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struct slow_work *slow_work_execs[SLOW_WORK_THREAD_LIMIT];
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pid_t slow_work_pids[SLOW_WORK_THREAD_LIMIT];
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DEFINE_RWLOCK(slow_work_execs_lock);
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#endif
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/*
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* The queues of work items and the lock governing access to them. These are
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* shared between all the CPUs. It doesn't make sense to have per-CPU queues
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* as the number of threads bears no relation to the number of CPUs.
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*
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* There are two queues of work items: one for slow work items, and one for
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* very slow work items.
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*/
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LIST_HEAD(slow_work_queue);
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LIST_HEAD(vslow_work_queue);
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DEFINE_SPINLOCK(slow_work_queue_lock);
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/*
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* The following are two wait queues that get pinged when a work item is placed
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* on an empty queue. These allow work items that are hogging a thread by
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* sleeping in a way that could be deferred to yield their thread and enqueue
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* themselves.
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*/
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static DECLARE_WAIT_QUEUE_HEAD(slow_work_queue_waits_for_occupation);
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static DECLARE_WAIT_QUEUE_HEAD(vslow_work_queue_waits_for_occupation);
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/*
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* The thread controls. A variable used to signal to the threads that they
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* should exit when the queue is empty, a waitqueue used by the threads to wait
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* for signals, and a completion set by the last thread to exit.
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*/
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static bool slow_work_threads_should_exit;
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static DECLARE_WAIT_QUEUE_HEAD(slow_work_thread_wq);
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static DECLARE_COMPLETION(slow_work_last_thread_exited);
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/*
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* The number of users of the thread pool and its lock. Whilst this is zero we
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* have no threads hanging around, and when this reaches zero, we wait for all
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* active or queued work items to complete and kill all the threads we do have.
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*/
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static int slow_work_user_count;
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static DEFINE_MUTEX(slow_work_user_lock);
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static inline int slow_work_get_ref(struct slow_work *work)
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{
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if (work->ops->get_ref)
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return work->ops->get_ref(work);
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return 0;
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}
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static inline void slow_work_put_ref(struct slow_work *work)
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{
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if (work->ops->put_ref)
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work->ops->put_ref(work);
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}
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/*
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* Calculate the maximum number of active threads in the pool that are
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* permitted to process very slow work items.
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*
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* The answer is rounded up to at least 1, but may not equal or exceed the
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* maximum number of the threads in the pool. This means we always have at
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* least one thread that can process slow work items, and we always have at
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* least one thread that won't get tied up doing so.
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*/
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static unsigned slow_work_calc_vsmax(void)
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{
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unsigned vsmax;
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vsmax = atomic_read(&slow_work_thread_count) * vslow_work_proportion;
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vsmax /= 100;
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vsmax = max(vsmax, 1U);
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return min(vsmax, slow_work_max_threads - 1);
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}
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/*
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* Attempt to execute stuff queued on a slow thread. Return true if we managed
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* it, false if there was nothing to do.
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*/
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static noinline bool slow_work_execute(int id)
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{
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struct slow_work *work = NULL;
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unsigned vsmax;
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bool very_slow;
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vsmax = slow_work_calc_vsmax();
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/* see if we can schedule a new thread to be started if we're not
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* keeping up with the work */
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if (!waitqueue_active(&slow_work_thread_wq) &&
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(!list_empty(&slow_work_queue) || !list_empty(&vslow_work_queue)) &&
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atomic_read(&slow_work_thread_count) < slow_work_max_threads &&
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!slow_work_may_not_start_new_thread)
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slow_work_enqueue(&slow_work_new_thread);
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/* find something to execute */
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spin_lock_irq(&slow_work_queue_lock);
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if (!list_empty(&vslow_work_queue) &&
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atomic_read(&vslow_work_executing_count) < vsmax) {
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work = list_entry(vslow_work_queue.next,
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struct slow_work, link);
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if (test_and_set_bit_lock(SLOW_WORK_EXECUTING, &work->flags))
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BUG();
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list_del_init(&work->link);
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atomic_inc(&vslow_work_executing_count);
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very_slow = true;
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} else if (!list_empty(&slow_work_queue)) {
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work = list_entry(slow_work_queue.next,
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struct slow_work, link);
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if (test_and_set_bit_lock(SLOW_WORK_EXECUTING, &work->flags))
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BUG();
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list_del_init(&work->link);
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very_slow = false;
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} else {
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very_slow = false; /* avoid the compiler warning */
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}
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slow_work_set_thread_processing(id, work);
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if (work) {
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slow_work_mark_time(work);
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slow_work_begin_exec(id, work);
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}
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spin_unlock_irq(&slow_work_queue_lock);
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if (!work)
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return false;
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if (!test_and_clear_bit(SLOW_WORK_PENDING, &work->flags))
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BUG();
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/* don't execute if the work is in the process of being cancelled */
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if (!test_bit(SLOW_WORK_CANCELLING, &work->flags))
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work->ops->execute(work);
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if (very_slow)
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atomic_dec(&vslow_work_executing_count);
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clear_bit_unlock(SLOW_WORK_EXECUTING, &work->flags);
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/* wake up anyone waiting for this work to be complete */
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wake_up_bit(&work->flags, SLOW_WORK_EXECUTING);
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slow_work_end_exec(id, work);
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/* if someone tried to enqueue the item whilst we were executing it,
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* then it'll be left unenqueued to avoid multiple threads trying to
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* execute it simultaneously
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*
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* there is, however, a race between us testing the pending flag and
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* getting the spinlock, and between the enqueuer setting the pending
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* flag and getting the spinlock, so we use a deferral bit to tell us
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* if the enqueuer got there first
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*/
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if (test_bit(SLOW_WORK_PENDING, &work->flags)) {
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spin_lock_irq(&slow_work_queue_lock);
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if (!test_bit(SLOW_WORK_EXECUTING, &work->flags) &&
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test_and_clear_bit(SLOW_WORK_ENQ_DEFERRED, &work->flags))
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goto auto_requeue;
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spin_unlock_irq(&slow_work_queue_lock);
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}
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/* sort out the race between module unloading and put_ref() */
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slow_work_put_ref(work);
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slow_work_done_thread_processing(id, work);
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return true;
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auto_requeue:
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/* we must complete the enqueue operation
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* - we transfer our ref on the item back to the appropriate queue
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* - don't wake another thread up as we're awake already
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*/
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slow_work_mark_time(work);
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if (test_bit(SLOW_WORK_VERY_SLOW, &work->flags))
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list_add_tail(&work->link, &vslow_work_queue);
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else
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list_add_tail(&work->link, &slow_work_queue);
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spin_unlock_irq(&slow_work_queue_lock);
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slow_work_clear_thread_processing(id);
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return true;
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}
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/**
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* slow_work_sleep_till_thread_needed - Sleep till thread needed by other work
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* work: The work item under execution that wants to sleep
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* _timeout: Scheduler sleep timeout
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*
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* Allow a requeueable work item to sleep on a slow-work processor thread until
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* that thread is needed to do some other work or the sleep is interrupted by
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* some other event.
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*
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* The caller must set up a wake up event before calling this and must have set
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* the appropriate sleep mode (such as TASK_UNINTERRUPTIBLE) and tested its own
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* condition before calling this function as no test is made here.
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*
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* False is returned if there is nothing on the queue; true is returned if the
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* work item should be requeued
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*/
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bool slow_work_sleep_till_thread_needed(struct slow_work *work,
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signed long *_timeout)
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{
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wait_queue_head_t *wfo_wq;
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struct list_head *queue;
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DEFINE_WAIT(wait);
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if (test_bit(SLOW_WORK_VERY_SLOW, &work->flags)) {
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wfo_wq = &vslow_work_queue_waits_for_occupation;
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queue = &vslow_work_queue;
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} else {
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wfo_wq = &slow_work_queue_waits_for_occupation;
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queue = &slow_work_queue;
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}
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if (!list_empty(queue))
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return true;
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add_wait_queue_exclusive(wfo_wq, &wait);
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if (list_empty(queue))
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*_timeout = schedule_timeout(*_timeout);
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finish_wait(wfo_wq, &wait);
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return !list_empty(queue);
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}
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EXPORT_SYMBOL(slow_work_sleep_till_thread_needed);
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/**
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* slow_work_enqueue - Schedule a slow work item for processing
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* @work: The work item to queue
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*
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* Schedule a slow work item for processing. If the item is already undergoing
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* execution, this guarantees not to re-enter the execution routine until the
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* first execution finishes.
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*
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* The item is pinned by this function as it retains a reference to it, managed
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* through the item operations. The item is unpinned once it has been
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* executed.
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*
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* An item may hog the thread that is running it for a relatively large amount
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* of time, sufficient, for example, to perform several lookup, mkdir, create
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* and setxattr operations. It may sleep on I/O and may sleep to obtain locks.
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*
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* Conversely, if a number of items are awaiting processing, it may take some
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* time before any given item is given attention. The number of threads in the
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* pool may be increased to deal with demand, but only up to a limit.
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*
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* If SLOW_WORK_VERY_SLOW is set on the work item, then it will be placed in
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* the very slow queue, from which only a portion of the threads will be
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* allowed to pick items to execute. This ensures that very slow items won't
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* overly block ones that are just ordinarily slow.
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*
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* Returns 0 if successful, -EAGAIN if not (or -ECANCELED if cancelled work is
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* attempted queued)
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*/
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int slow_work_enqueue(struct slow_work *work)
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{
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wait_queue_head_t *wfo_wq;
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struct list_head *queue;
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unsigned long flags;
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int ret;
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if (test_bit(SLOW_WORK_CANCELLING, &work->flags))
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return -ECANCELED;
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BUG_ON(slow_work_user_count <= 0);
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BUG_ON(!work);
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BUG_ON(!work->ops);
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/* when honouring an enqueue request, we only promise that we will run
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* the work function in the future; we do not promise to run it once
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* per enqueue request
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*
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* we use the PENDING bit to merge together repeat requests without
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* having to disable IRQs and take the spinlock, whilst still
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* maintaining our promise
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*/
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if (!test_and_set_bit_lock(SLOW_WORK_PENDING, &work->flags)) {
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if (test_bit(SLOW_WORK_VERY_SLOW, &work->flags)) {
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wfo_wq = &vslow_work_queue_waits_for_occupation;
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queue = &vslow_work_queue;
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} else {
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wfo_wq = &slow_work_queue_waits_for_occupation;
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queue = &slow_work_queue;
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}
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spin_lock_irqsave(&slow_work_queue_lock, flags);
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if (unlikely(test_bit(SLOW_WORK_CANCELLING, &work->flags)))
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goto cancelled;
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/* we promise that we will not attempt to execute the work
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* function in more than one thread simultaneously
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*
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* this, however, leaves us with a problem if we're asked to
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* enqueue the work whilst someone is executing the work
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* function as simply queueing the work immediately means that
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* another thread may try executing it whilst it is already
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* under execution
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*
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* to deal with this, we set the ENQ_DEFERRED bit instead of
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* enqueueing, and the thread currently executing the work
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* function will enqueue the work item when the work function
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* returns and it has cleared the EXECUTING bit
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*/
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if (test_bit(SLOW_WORK_EXECUTING, &work->flags)) {
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set_bit(SLOW_WORK_ENQ_DEFERRED, &work->flags);
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} else {
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ret = slow_work_get_ref(work);
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if (ret < 0)
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goto failed;
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slow_work_mark_time(work);
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list_add_tail(&work->link, queue);
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wake_up(&slow_work_thread_wq);
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/* if someone who could be requeued is sleeping on a
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* thread, then ask them to yield their thread */
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if (work->link.prev == queue)
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wake_up(wfo_wq);
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}
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spin_unlock_irqrestore(&slow_work_queue_lock, flags);
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}
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return 0;
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cancelled:
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ret = -ECANCELED;
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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 = work->ops->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);
|