[PATCH] closures: move to lib/

Kent Overstreet
2013-12-19T01:30:21Z

the closure code was never intended to be bcache specific - hopefully it can be
useful elsewhere in the kernel.

Signed-off-by: Kent Overstreet <kmo@daterainc.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
---
drivers/md/bcache/Kconfig | 9 -
drivers/md/bcache/Makefile | 2 +-
drivers/md/bcache/bcache.h | 2 +-
drivers/md/bcache/closure.c | 222 ----------------------
drivers/md/bcache/closure.h | 453 --------------------------------------------
drivers/md/bcache/util.h | 3 +-
include/linux/closure.h | 451 +++++++++++++++++++++++++++++++++++++++++++
lib/Kconfig.debug | 8 +
lib/Makefile | 2 +-
lib/closure.c | 218 +++++++++++++++++++++
10 files changed, 681 insertions(+), 689 deletions(-)
delete mode 100644 drivers/md/bcache/closure.c
delete mode 100644 drivers/md/bcache/closure.h
create mode 100644 include/linux/closure.h
create mode 100644 lib/closure.c

diff --git a/drivers/md/bcache/Kconfig b/drivers/md/bcache/Kconfig
index 2638417b19..d6d7f792cc 100644
--- a/drivers/md/bcache/Kconfig
+++ b/drivers/md/bcache/Kconfig
@@ -16,15 +16,6 @@ config BCACHE_DEBUG
Enables extra debugging tools, allows expensive runtime checks to be
turned on.

-config BCACHE_CLOSURES_DEBUG
- bool "Debug closures"
- depends on BCACHE
- select DEBUG_FS
- ---help---
- Keeps all active closures in a linked list and provides a debugfs
- interface to list them, which makes it possible to see asynchronous
- operations that get stuck.
-
# cgroup code needs to be updated:
#
#config CGROUP_BCACHE
diff --git a/drivers/md/bcache/Makefile b/drivers/md/bcache/Makefile
index 0e9c82523b..17ab9adbdf 100644
--- a/drivers/md/bcache/Makefile
+++ b/drivers/md/bcache/Makefile
@@ -2,6 +2,6 @@
obj-$(CONFIG_BCACHE) += bcache.o

bcache-y := alloc.o btree.o bset.o io.o journal.o writeback.o\
- movinggc.o request.o super.o sysfs.o debug.o util.o trace.o stats.o closure.o
+ movinggc.o request.o super.o sysfs.o debug.o util.o trace.o stats.o

CFLAGS_request.o += -Iblock
diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h
index 9d062bc562..79f444a8b9 100644
--- a/drivers/md/bcache/bcache.h
+++ b/drivers/md/bcache/bcache.h
@@ -179,6 +179,7 @@

#include <linux/bcache.h>
#include <linux/bio.h>
+#include <linux/closure.h>
#include <linux/kobject.h>
#include <linux/list.h>
#include <linux/mutex.h>
@@ -188,7 +189,6 @@
#include <linux/workqueue.h>

#include "util.h"
-#include "closure.h"

struct bucket {
atomic_t pin;
diff --git a/drivers/md/bcache/closure.c b/drivers/md/bcache/closure.c
deleted file mode 100644
index 7a228de95f..0000000000
--- a/drivers/md/bcache/closure.c
+++ /dev/null
@@ -1,222 +0,0 @@
-/*
- * Asynchronous refcounty things
- *
- * Copyright 2010, 2011 Kent Overstreet <kent.overstreet@gmail.com>
- * Copyright 2012 Google, Inc.
- */
-
-#include <linux/debugfs.h>
-#include <linux/module.h>
-#include <linux/seq_file.h>
-
-#include "closure.h"
-
-static inline void closure_put_after_sub(struct closure *cl, int flags)
-{
- int r = flags & CLOSURE_REMAINING_MASK;
-
- BUG_ON(flags & CLOSURE_GUARD_MASK);
- BUG_ON(!r && (flags & ~CLOSURE_DESTRUCTOR));
-
- /* Must deliver precisely one wakeup */
- if (r == 1 && (flags & CLOSURE_SLEEPING))
- wake_up_process(cl->task);
-
- if (!r) {
- if (cl->fn && !(flags & CLOSURE_DESTRUCTOR)) {
- atomic_set(&cl->remaining,
- CLOSURE_REMAINING_INITIALIZER);
- closure_queue(cl);
- } else {
- struct closure *parent = cl->parent;
- closure_fn *destructor = cl->fn;
-
- closure_debug_destroy(cl);
-
- if (destructor)
- destructor(cl);
-
- if (parent)
- closure_put(parent);
- }
- }
-}
-
-/* For clearing flags with the same atomic op as a put */
-void closure_sub(struct closure *cl, int v)
-{
- closure_put_after_sub(cl, atomic_sub_return(v, &cl->remaining));
-}
-EXPORT_SYMBOL(closure_sub);
-
-/**
- * closure_put - decrement a closure's refcount
- */
-void closure_put(struct closure *cl)
-{
- closure_put_after_sub(cl, atomic_dec_return(&cl->remaining));
-}
-EXPORT_SYMBOL(closure_put);
-
-/**
- * closure_wake_up - wake up all closures on a wait list, without memory barrier
- */
-void __closure_wake_up(struct closure_waitlist *wait_list)
-{
- struct llist_node *list;
- struct closure *cl;
- struct llist_node *reverse = NULL;
-
- list = llist_del_all(&wait_list->list);
-
- /* We first reverse the list to preserve FIFO ordering and fairness */
-
- while (list) {
- struct llist_node *t = list;
- list = llist_next(list);
-
- t->next = reverse;
- reverse = t;
- }
-
- /* Then do the wakeups */
-
- while (reverse) {
- cl = container_of(reverse, struct closure, list);
- reverse = llist_next(reverse);
-
- closure_set_waiting(cl, 0);
- closure_sub(cl, CLOSURE_WAITING + 1);
- }
-}
-EXPORT_SYMBOL(__closure_wake_up);
-
-/**
- * closure_wait - add a closure to a waitlist
- *
- * @waitlist will own a ref on @cl, which will be released when
- * closure_wake_up() is called on @waitlist.
- *
- */
-bool closure_wait(struct closure_waitlist *waitlist, struct closure *cl)
-{
- if (atomic_read(&cl->remaining) & CLOSURE_WAITING)
- return false;
-
- closure_set_waiting(cl, _RET_IP_);
- atomic_add(CLOSURE_WAITING + 1, &cl->remaining);
- llist_add(&cl->list, &waitlist->list);
-
- return true;
-}
-EXPORT_SYMBOL(closure_wait);
-
-/**
- * closure_sync - sleep until a closure a closure has nothing left to wait on
- *
- * Sleeps until the refcount hits 1 - the thread that's running the closure owns
- * the last refcount.
- */
-void closure_sync(struct closure *cl)
-{
- while (1) {
- __closure_start_sleep(cl);
- closure_set_ret_ip(cl);
-
- if ((atomic_read(&cl->remaining) &
- CLOSURE_REMAINING_MASK) == 1)
- break;
-
- schedule();
- }
-
- __closure_end_sleep(cl);
-}
-EXPORT_SYMBOL(closure_sync);
-
-#ifdef CONFIG_BCACHE_CLOSURES_DEBUG
-
-static LIST_HEAD(closure_list);
-static DEFINE_SPINLOCK(closure_list_lock);
-
-void closure_debug_create(struct closure *cl)
-{
- unsigned long flags;
-
- BUG_ON(cl->magic == CLOSURE_MAGIC_ALIVE);
- cl->magic = CLOSURE_MAGIC_ALIVE;
-
- spin_lock_irqsave(&closure_list_lock, flags);
- list_add(&cl->all, &closure_list);
- spin_unlock_irqrestore(&closure_list_lock, flags);
-}
-EXPORT_SYMBOL(closure_debug_create);
-
-void closure_debug_destroy(struct closure *cl)
-{
- unsigned long flags;
-
- BUG_ON(cl->magic != CLOSURE_MAGIC_ALIVE);
- cl->magic = CLOSURE_MAGIC_DEAD;
-
- spin_lock_irqsave(&closure_list_lock, flags);
- list_del(&cl->all);
- spin_unlock_irqrestore(&closure_list_lock, flags);
-}
-EXPORT_SYMBOL(closure_debug_destroy);
-
-static struct dentry *debug;
-
-#define work_data_bits(work) ((unsigned long *)(&(work)->data))
-
-static int debug_seq_show(struct seq_file *f, void *data)
-{
- struct closure *cl;
- spin_lock_irq(&closure_list_lock);
-
- list_for_each_entry(cl, &closure_list, all) {
- int r = atomic_read(&cl->remaining);
-
- seq_printf(f, "%p: %pF -> %pf p %p r %i ",
- cl, (void *) cl->ip, cl->fn, cl->parent,
- r & CLOSURE_REMAINING_MASK);
-
- seq_printf(f, "%s%s%s%s\n",
- test_bit(WORK_STRUCT_PENDING,
- work_data_bits(&cl->work)) ? "Q" : "",
- r & CLOSURE_RUNNING ? "R" : "",
- r & CLOSURE_STACK ? "S" : "",
- r & CLOSURE_SLEEPING ? "Sl" : "");
-
- if (r & CLOSURE_WAITING)
- seq_printf(f, " W %pF\n",
- (void *) cl->waiting_on);
-
- seq_printf(f, "\n");
- }
-
- spin_unlock_irq(&closure_list_lock);
- return 0;
-}
-
-static int debug_seq_open(struct inode *inode, struct file *file)
-{
- return single_open(file, debug_seq_show, NULL);
-}
-
-static const struct file_operations debug_ops = {
- .owner = THIS_MODULE,
- .open = debug_seq_open,
- .read = seq_read,
- .release = single_release
-};
-
-void __init closure_debug_init(void)
-{
- debug = debugfs_create_file("closures", 0400, NULL, NULL, &debug_ops);
-}
-
-#endif
-
-MODULE_AUTHOR("Kent Overstreet <koverstreet@google.com>");
-MODULE_LICENSE("GPL");
diff --git a/drivers/md/bcache/closure.h b/drivers/md/bcache/closure.h
deleted file mode 100644
index 13c3aa2157..0000000000
--- a/drivers/md/bcache/closure.h
+++ /dev/null
@@ -1,453 +0,0 @@
-#ifndef _LINUX_CLOSURE_H
-#define _LINUX_CLOSURE_H
-
-#include <linux/llist.h>
-#include <linux/sched.h>
-#include <linux/workqueue.h>
-
-/*
- * Closure is perhaps the most overused and abused term in computer science, but
- * since I've been unable to come up with anything better you're stuck with it
- * again.
- *
- * What are closures?
- *
- * They embed a refcount. The basic idea is they count "things that are in
- * progress" - in flight bios, some other thread that's doing something else -
- * anything you might want to wait on.
- *
- * The refcount may be manipulated with closure_get() and closure_put().
- * closure_put() is where many of the interesting things happen, when it causes
- * the refcount to go to 0.
- *
- * Closures can be used to wait on things both synchronously and asynchronously,
- * and synchronous and asynchronous use can be mixed without restriction. To
- * wait synchronously, use closure_sync() - you will sleep until your closure's
- * refcount hits 1.
- *
- * To wait asynchronously, use
- * continue_at(cl, next_function, workqueue);
- *
- * passing it, as you might expect, the function to run when nothing is pending
- * and the workqueue to run that function out of.
- *
- * continue_at() also, critically, is a macro that returns the calling function.
- * There's good reason for this.
- *
- * To use safely closures asynchronously, they must always have a refcount while
- * they are running owned by the thread that is running them. Otherwise, suppose
- * you submit some bios and wish to have a function run when they all complete:
- *
- * foo_endio(struct bio *bio, int error)
- * {
- * closure_put(cl);
- * }
- *
- * closure_init(cl);
- *
- * do_stuff();
- * closure_get(cl);
- * bio1->bi_endio = foo_endio;
- * bio_submit(bio1);
- *
- * do_more_stuff();
- * closure_get(cl);
- * bio2->bi_endio = foo_endio;
- * bio_submit(bio2);
- *
- * continue_at(cl, complete_some_read, system_wq);
- *
- * If closure's refcount started at 0, complete_some_read() could run before the
- * second bio was submitted - which is almost always not what you want! More
- * importantly, it wouldn't be possible to say whether the original thread or
- * complete_some_read()'s thread owned the closure - and whatever state it was
- * associated with!
- *
- * So, closure_init() initializes a closure's refcount to 1 - and when a
- * closure_fn is run, the refcount will be reset to 1 first.
- *
- * Then, the rule is - if you got the refcount with closure_get(), release it
- * with closure_put() (i.e, in a bio->bi_endio function). If you have a refcount
- * on a closure because you called closure_init() or you were run out of a
- * closure - _always_ use continue_at(). Doing so consistently will help
- * eliminate an entire class of particularly pernicious races.
- *
- * For a closure to wait on an arbitrary event, we need to introduce waitlists:
- *
- * struct closure_waitlist list;
- * closure_wait_event(list, cl, condition);
- * closure_wake_up(wait_list);
- *
- * These work analagously to wait_event() and wake_up() - except that instead of
- * operating on the current thread (for wait_event()) and lists of threads, they
- * operate on an explicit closure and lists of closures.
- *
- * Because it's a closure we can now wait either synchronously or
- * asynchronously. closure_wait_event() returns the current value of the
- * condition, and if it returned false continue_at() or closure_sync() can be
- * used to wait for it to become true.
- *
- * It's useful for waiting on things when you can't sleep in the context in
- * which you must check the condition (perhaps a spinlock held, or you might be
- * beneath generic_make_request() - in which case you can't sleep on IO).
- *
- * closure_wait_event() will wait either synchronously or asynchronously,
- * depending on whether the closure is in blocking mode or not. You can pick a
- * mode explicitly with closure_wait_event_sync() and
- * closure_wait_event_async(), which do just what you might expect.
- *
- * Lastly, you might have a wait list dedicated to a specific event, and have no
- * need for specifying the condition - you just want to wait until someone runs
- * closure_wake_up() on the appropriate wait list. In that case, just use
- * closure_wait(). It will return either true or false, depending on whether the
- * closure was already on a wait list or not - a closure can only be on one wait
- * list at a time.
- *
- * Parents:
- *
- * closure_init() takes two arguments - it takes the closure to initialize, and
- * a (possibly null) parent.
- *
- * If parent is non null, the new closure will have a refcount for its lifetime;
- * a closure is considered to be "finished" when its refcount hits 0 and the
- * function to run is null. Hence
- *
- * continue_at(cl, NULL, NULL);
- *
- * returns up the (spaghetti) stack of closures, precisely like normal return
- * returns up the C stack. continue_at() with non null fn is better thought of
- * as doing a tail call.
- *
- * All this implies that a closure should typically be embedded in a particular
- * struct (which its refcount will normally control the lifetime of), and that
- * struct can very much be thought of as a stack frame.
- */
-
-struct closure;
-typedef void (closure_fn) (struct closure *);
-
-struct closure_waitlist {
- struct llist_head list;
-};
-
-enum closure_state {
- /*
- * CLOSURE_WAITING: Set iff the closure is on a waitlist. Must be set by
- * the thread that owns the closure, and cleared by the thread that's
- * waking up the closure.
- *
- * CLOSURE_SLEEPING: Must be set before a thread uses a closure to sleep
- * - indicates that cl->task is valid and closure_put() may wake it up.
- * Only set or cleared by the thread that owns the closure.
- *
- * The rest are for debugging and don't affect behaviour:
- *
- * CLOSURE_RUNNING: Set when a closure is running (i.e. by
- * closure_init() and when closure_put() runs then next function), and
- * must be cleared before remaining hits 0. Primarily to help guard
- * against incorrect usage and accidentally transferring references.
- * continue_at() and closure_return() clear it for you, if you're doing
- * something unusual you can use closure_set_dead() which also helps
- * annotate where references are being transferred.
- *
- * CLOSURE_STACK: Sanity check - remaining should never hit 0 on a
- * closure with this flag set
- */
-
- CLOSURE_BITS_START = (1 << 23),
- CLOSURE_DESTRUCTOR = (1 << 23),
- CLOSURE_WAITING = (1 << 25),
- CLOSURE_SLEEPING = (1 << 27),
- CLOSURE_RUNNING = (1 << 29),
- CLOSURE_STACK = (1 << 31),
-};
-
-#define CLOSURE_GUARD_MASK \
- ((CLOSURE_DESTRUCTOR|CLOSURE_WAITING|CLOSURE_SLEEPING| \
- CLOSURE_RUNNING|CLOSURE_STACK) << 1)
-
-#define CLOSURE_REMAINING_MASK (CLOSURE_BITS_START - 1)
-#define CLOSURE_REMAINING_INITIALIZER (1|CLOSURE_RUNNING)
-
-struct closure {
- union {
- struct {
- struct workqueue_struct *wq;
- struct task_struct *task;
- struct llist_node list;
- closure_fn *fn;
- };
- struct work_struct work;
- };
-
- struct closure *parent;
-
- atomic_t remaining;
-
-#ifdef CONFIG_BCACHE_CLOSURES_DEBUG
-#define CLOSURE_MAGIC_DEAD 0xc054dead
-#define CLOSURE_MAGIC_ALIVE 0xc054a11e
-
- unsigned magic;
- struct list_head all;
- unsigned long ip;
- unsigned long waiting_on;
-#endif
-};
-
-void closure_sub(struct closure *cl, int v);
-void closure_put(struct closure *cl);
-void __closure_wake_up(struct closure_waitlist *list);
-bool closure_wait(struct closure_waitlist *list, struct closure *cl);
-void closure_sync(struct closure *cl);
-
-#ifdef CONFIG_BCACHE_CLOSURES_DEBUG
-
-void closure_debug_init(void);
-void closure_debug_create(struct closure *cl);
-void closure_debug_destroy(struct closure *cl);
-
-#else
-
-static inline void closure_debug_init(void) {}
-static inline void closure_debug_create(struct closure *cl) {}
-static inline void closure_debug_destroy(struct closure *cl) {}
-
-#endif
-
-static inline void closure_set_ip(struct closure *cl)
-{
-#ifdef CONFIG_BCACHE_CLOSURES_DEBUG
- cl->ip = _THIS_IP_;
-#endif
-}
-
-static inline void closure_set_ret_ip(struct closure *cl)
-{
-#ifdef CONFIG_BCACHE_CLOSURES_DEBUG
- cl->ip = _RET_IP_;
-#endif
-}
-
-static inline void closure_set_waiting(struct closure *cl, unsigned long f)
-{
-#ifdef CONFIG_BCACHE_CLOSURES_DEBUG
- cl->waiting_on = f;
-#endif
-}
-
-static inline void __closure_end_sleep(struct closure *cl)
-{
- __set_current_state(TASK_RUNNING);
-
- if (atomic_read(&cl->remaining) & CLOSURE_SLEEPING)
- atomic_sub(CLOSURE_SLEEPING, &cl->remaining);
-}
-
-static inline void __closure_start_sleep(struct closure *cl)
-{
- closure_set_ip(cl);
- cl->task = current;
- set_current_state(TASK_UNINTERRUPTIBLE);
-
- if (!(atomic_read(&cl->remaining) & CLOSURE_SLEEPING))
- atomic_add(CLOSURE_SLEEPING, &cl->remaining);
-}
-
-static inline void closure_set_stopped(struct closure *cl)
-{
- atomic_sub(CLOSURE_RUNNING, &cl->remaining);
-}
-
-static inline void set_closure_fn(struct closure *cl, closure_fn *fn,
- struct workqueue_struct *wq)
-{
- BUG_ON(object_is_on_stack(cl));
- closure_set_ip(cl);
- cl->fn = fn;
- cl->wq = wq;
- /* between atomic_dec() in closure_put() */
- smp_mb__before_atomic_dec();
-}
-
-static inline void closure_queue(struct closure *cl)
-{
- struct workqueue_struct *wq = cl->wq;
- if (wq) {
- INIT_WORK(&cl->work, cl->work.func);
- BUG_ON(!queue_work(wq, &cl->work));
- } else
- cl->fn(cl);
-}
-
-/**
- * closure_get - increment a closure's refcount
- */
-static inline void closure_get(struct closure *cl)
-{
-#ifdef CONFIG_BCACHE_CLOSURES_DEBUG
- BUG_ON((atomic_inc_return(&cl->remaining) &
- CLOSURE_REMAINING_MASK) <= 1);
-#else
- atomic_inc(&cl->remaining);
-#endif
-}
-
-/**
- * closure_init - Initialize a closure, setting the refcount to 1
- * @cl: closure to initialize
- * @parent: parent of the new closure. cl will take a refcount on it for its
- * lifetime; may be NULL.
- */
-static inline void closure_init(struct closure *cl, struct closure *parent)
-{
- memset(cl, 0, sizeof(struct closure));
- cl->parent = parent;
- if (parent)
- closure_get(parent);
-
- atomic_set(&cl->remaining, CLOSURE_REMAINING_INITIALIZER);
-
- closure_debug_create(cl);
- closure_set_ip(cl);
-}
-
-static inline void closure_init_stack(struct closure *cl)
-{
- memset(cl, 0, sizeof(struct closure));
- atomic_set(&cl->remaining, CLOSURE_REMAINING_INITIALIZER|CLOSURE_STACK);
-}
-
-/**
- * closure_wake_up - wake up all closures on a wait list.
- */
-static inline void closure_wake_up(struct closure_waitlist *list)
-{
- smp_mb();
- __closure_wake_up(list);
-}
-
-/**
- * closure_wait_event - wait on arbitrary event
- *
- * Analogous to wait_event() but for closures.
- *
- * The loop is oddly structured so as to avoid a race; we must check the
- * condition again after we've added ourself to the waitlist. We know if we were
- * already on the waitlist because closure_wait() returns false; thus, we only
- * schedule or break if closure_wait() returns false. If it returns true, we
- * just loop again - rechecking the condition.
- *
- * The __closure_wake_up() is necessary because we may race with the event
- * becoming true; i.e. we see event false -> wait -> recheck condition, but the
- * thread that made the event true may have called closure_wake_up() before we
- * added ourself to the wait list.
- *
- * We have to call closure_sync() at the end instead of just
- * __closure_end_sleep() because a different thread might've called
- * closure_wake_up() before us and gotten preempted before they dropped the
- * refcount on our closure. If this was a stack allocated closure, that would be
- * bad.
- */
-#define closure_wait_event(list, cl, condition) \
-({ \
- typeof(condition) ret; \
- \
- while (1) { \
- ret = (condition); \
- if (ret) { \
- __closure_wake_up(list); \
- closure_sync(cl); \
- break; \
- } \
- \
- __closure_start_sleep(cl); \
- \
- if (!closure_wait(list, cl)) \
- schedule(); \
- } \
- \
- ret; \
-})
-
-/**
- * continue_at - jump to another function with barrier
- *
- * After @cl is no longer waiting on anything (i.e. all outstanding refs have
- * been dropped with closure_put()), it will resume execution at @fn running out
- * of @wq (or, if @wq is NULL, @fn will be called by closure_put() directly).
- *
- * NOTE: This macro expands to a return in the calling function!
- *
- * This is because after calling continue_at() you no longer have a ref on @cl,
- * and whatever @cl owns may be freed out from under you - a running closure fn
- * has a ref on its own closure which continue_at() drops.
- */
-#define continue_at(_cl, _fn, _wq) \
-do { \
- set_closure_fn(_cl, _fn, _wq); \
- closure_sub(_cl, CLOSURE_RUNNING + 1); \
- return; \
-} while (0)
-
-/**
- * closure_return - finish execution of a closure
- *
- * This is used to indicate that @cl is finished: when all outstanding refs on
- * @cl have been dropped @cl's ref on its parent closure (as passed to
- * closure_init()) will be dropped, if one was specified - thus this can be
- * thought of as returning to the parent closure.
- */
-#define closure_return(_cl) continue_at((_cl), NULL, NULL)
-
-/**
- * continue_at_nobarrier - jump to another function without barrier
- *
- * Causes @fn to be executed out of @cl, in @wq context (or called directly if
- * @wq is NULL).
- *
- * NOTE: like continue_at(), this macro expands to a return in the caller!
- *
- * The ref the caller of continue_at_nobarrier() had on @cl is now owned by @fn,
- * thus it's not safe to touch anything protected by @cl after a
- * continue_at_nobarrier().
- */
-#define continue_at_nobarrier(_cl, _fn, _wq) \
-do { \
- set_closure_fn(_cl, _fn, _wq); \
- closure_queue(_cl); \
- return; \
-} while (0)
-
-/**
- * closure_return - finish execution of a closure, with destructor
- *
- * Works like closure_return(), except @destructor will be called when all
- * outstanding refs on @cl have been dropped; @destructor may be used to safely
- * free the memory occupied by @cl, and it is called with the ref on the parent
- * closure still held - so @destructor could safely return an item to a
- * freelist protected by @cl's parent.
- */
-#define closure_return_with_destructor(_cl, _destructor) \
-do { \
- set_closure_fn(_cl, _destructor, NULL); \
- closure_sub(_cl, CLOSURE_RUNNING - CLOSURE_DESTRUCTOR + 1); \
- return; \
-} while (0)
-
-/**
- * closure_call - execute @fn out of a new, uninitialized closure
- *
- * Typically used when running out of one closure, and we want to run @fn
- * asynchronously out of a new closure - @parent will then wait for @cl to
- * finish.
- */
-static inline void closure_call(struct closure *cl, closure_fn fn,
- struct workqueue_struct *wq,
- struct closure *parent)
-{
- closure_init(cl, parent);
- continue_at_nobarrier(cl, fn, wq);
-}
-
-#endif /* _LINUX_CLOSURE_H */
diff --git a/drivers/md/bcache/util.h b/drivers/md/bcache/util.h
index 1030c6020e..c51605d34b 100644
--- a/drivers/md/bcache/util.h
+++ b/drivers/md/bcache/util.h
@@ -2,6 +2,7 @@
#ifndef _BCACHE_UTIL_H
#define _BCACHE_UTIL_H

+#include <linux/closure.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/llist.h>
@@ -9,8 +10,6 @@
#include <linux/vmalloc.h>
#include <linux/workqueue.h>

-#include "closure.h"
-
#define PAGE_SECTORS (PAGE_SIZE / 512)

struct closure;
diff --git a/include/linux/closure.h b/include/linux/closure.h
new file mode 100644
index 0000000000..038f0bf5df
--- /dev/null
+++ b/include/linux/closure.h
@@ -0,0 +1,451 @@
+#ifndef _LINUX_CLOSURE_H
+#define _LINUX_CLOSURE_H
+
+#include <linux/llist.h>
+#include <linux/sched.h>
+#include <linux/workqueue.h>
+
+/*
+ * Closure is perhaps the most overused and abused term in computer science, but
+ * since I've been unable to come up with anything better you're stuck with it
+ * again.
+ *
+ * What are closures?
+ *
+ * They embed a refcount. The basic idea is they count "things that are in
+ * progress" - in flight bios, some other thread that's doing something else -
+ * anything you might want to wait on.
+ *
+ * The refcount may be manipulated with closure_get() and closure_put().
+ * closure_put() is where many of the interesting things happen, when it causes
+ * the refcount to go to 0.
+ *
+ * Closures can be used to wait on things both synchronously and asynchronously,
+ * and synchronous and asynchronous use can be mixed without restriction. To
+ * wait synchronously, use closure_sync() - you will sleep until your closure's
+ * refcount hits 1.
+ *
+ * To wait asynchronously, use
+ * continue_at(cl, next_function, workqueue);
+ *
+ * passing it, as you might expect, the function to run when nothing is pending
+ * and the workqueue to run that function out of.
+ *
+ * continue_at() also, critically, is a macro that returns the calling function.
+ * There's good reason for this.
+ *
+ * To use safely closures asynchronously, they must always have a refcount while
+ * they are running owned by the thread that is running them. Otherwise, suppose
+ * you submit some bios and wish to have a function run when they all complete:
+ *
+ * foo_endio(struct bio *bio, int error)
+ * {
+ * closure_put(cl);
+ * }
+ *
+ * closure_init(cl);
+ *
+ * do_stuff();
+ * closure_get(cl);
+ * bio1->bi_endio = foo_endio;
+ * bio_submit(bio1);
+ *
+ * do_more_stuff();
+ * closure_get(cl);
+ * bio2->bi_endio = foo_endio;
+ * bio_submit(bio2);
+ *
+ * continue_at(cl, complete_some_read, system_wq);
+ *
+ * If closure's refcount started at 0, complete_some_read() could run before the
+ * second bio was submitted - which is almost always not what you want! More
+ * importantly, it wouldn't be possible to say whether the original thread or
+ * complete_some_read()'s thread owned the closure - and whatever state it was
+ * associated with!
+ *
+ * So, closure_init() initializes a closure's refcount to 1 - and when a
+ * closure_fn is run, the refcount will be reset to 1 first.
+ *
+ * Then, the rule is - if you got the refcount with closure_get(), release it
+ * with closure_put() (i.e, in a bio->bi_endio function). If you have a refcount
+ * on a closure because you called closure_init() or you were run out of a
+ * closure - _always_ use continue_at(). Doing so consistently will help
+ * eliminate an entire class of particularly pernicious races.
+ *
+ * For a closure to wait on an arbitrary event, we need to introduce waitlists:
+ *
+ * struct closure_waitlist list;
+ * closure_wait_event(list, cl, condition);
+ * closure_wake_up(wait_list);
+ *
+ * These work analagously to wait_event() and wake_up() - except that instead of
+ * operating on the current thread (for wait_event()) and lists of threads, they
+ * operate on an explicit closure and lists of closures.
+ *
+ * Because it's a closure we can now wait either synchronously or
+ * asynchronously. closure_wait_event() returns the current value of the
+ * condition, and if it returned false continue_at() or closure_sync() can be
+ * used to wait for it to become true.
+ *
+ * It's useful for waiting on things when you can't sleep in the context in
+ * which you must check the condition (perhaps a spinlock held, or you might be
+ * beneath generic_make_request() - in which case you can't sleep on IO).
+ *
+ * closure_wait_event() will wait either synchronously or asynchronously,
+ * depending on whether the closure is in blocking mode or not. You can pick a
+ * mode explicitly with closure_wait_event_sync() and
+ * closure_wait_event_async(), which do just what you might expect.
+ *
+ * Lastly, you might have a wait list dedicated to a specific event, and have no
+ * need for specifying the condition - you just want to wait until someone runs
+ * closure_wake_up() on the appropriate wait list. In that case, just use
+ * closure_wait(). It will return either true or false, depending on whether the
+ * closure was already on a wait list or not - a closure can only be on one wait
+ * list at a time.
+ *
+ * Parents:
+ *
+ * closure_init() takes two arguments - it takes the closure to initialize, and
+ * a (possibly null) parent.
+ *
+ * If parent is non null, the new closure will have a refcount for its lifetime;
+ * a closure is considered to be "finished" when its refcount hits 0 and the
+ * function to run is null. Hence
+ *
+ * continue_at(cl, NULL, NULL);
+ *
+ * returns up the (spaghetti) stack of closures, precisely like normal return
+ * returns up the C stack. continue_at() with non null fn is better thought of
+ * as doing a tail call.
+ *
+ * All this implies that a closure should typically be embedded in a particular
+ * struct (which its refcount will normally control the lifetime of), and that
+ * struct can very much be thought of as a stack frame.
+ */
+
+struct closure;
+typedef void (closure_fn) (struct closure *);
+
+struct closure_waitlist {
+ struct llist_head list;
+};
+
+enum closure_state {
+ /*
+ * CLOSURE_WAITING: Set iff the closure is on a waitlist. Must be set by
+ * the thread that owns the closure, and cleared by the thread that's
+ * waking up the closure.
+ *
+ * CLOSURE_SLEEPING: Must be set before a thread uses a closure to sleep
+ * - indicates that cl->task is valid and closure_put() may wake it up.
+ * Only set or cleared by the thread that owns the closure.
+ *
+ * The rest are for debugging and don't affect behaviour:
+ *
+ * CLOSURE_RUNNING: Set when a closure is running (i.e. by
+ * closure_init() and when closure_put() runs then next function), and
+ * must be cleared before remaining hits 0. Primarily to help guard
+ * against incorrect usage and accidentally transferring references.
+ * continue_at() and closure_return() clear it for you, if you're doing
+ * something unusual you can use closure_set_dead() which also helps
+ * annotate where references are being transferred.
+ *
+ * CLOSURE_STACK: Sanity check - remaining should never hit 0 on a
+ * closure with this flag set
+ */
+
+ CLOSURE_BITS_START = (1 << 23),
+ CLOSURE_DESTRUCTOR = (1 << 23),
+ CLOSURE_WAITING = (1 << 25),
+ CLOSURE_SLEEPING = (1 << 27),
+ CLOSURE_RUNNING = (1 << 29),
+ CLOSURE_STACK = (1 << 31),
+};
+
+#define CLOSURE_GUARD_MASK \
+ ((CLOSURE_DESTRUCTOR|CLOSURE_WAITING|CLOSURE_SLEEPING| \
+ CLOSURE_RUNNING|CLOSURE_STACK) << 1)
+
+#define CLOSURE_REMAINING_MASK (CLOSURE_BITS_START - 1)
+#define CLOSURE_REMAINING_INITIALIZER (1|CLOSURE_RUNNING)
+
+struct closure {
+ union {
+ struct {
+ struct workqueue_struct *wq;
+ struct task_struct *task;
+ struct llist_node list;
+ closure_fn *fn;
+ };
+ struct work_struct work;
+ };
+
+ struct closure *parent;
+
+ atomic_t remaining;
+
+#ifdef CONFIG_CLOSURE_DEBUG
+#define CLOSURE_MAGIC_DEAD 0xc054dead
+#define CLOSURE_MAGIC_ALIVE 0xc054a11e
+
+ unsigned magic;
+ struct list_head all;
+ unsigned long ip;
+ unsigned long waiting_on;
+#endif
+};
+
+void closure_sub(struct closure *cl, int v);
+void closure_put(struct closure *cl);
+void __closure_wake_up(struct closure_waitlist *list);
+bool closure_wait(struct closure_waitlist *list, struct closure *cl);
+void closure_sync(struct closure *cl);
+
+#ifdef CONFIG_CLOSURE_DEBUG
+
+void closure_debug_create(struct closure *cl);
+void closure_debug_destroy(struct closure *cl);
+
+#else
+
+static inline void closure_debug_create(struct closure *cl) {}
+static inline void closure_debug_destroy(struct closure *cl) {}
+
+#endif
+
+static inline void closure_set_ip(struct closure *cl)
+{
+#ifdef CONFIG_CLOSURE_DEBUG
+ cl->ip = _THIS_IP_;
+#endif
+}
+
+static inline void closure_set_ret_ip(struct closure *cl)
+{
+#ifdef CONFIG_CLOSURE_DEBUG
+ cl->ip = _RET_IP_;
+#endif
+}
+
+static inline void closure_set_waiting(struct closure *cl, unsigned long f)
+{
+#ifdef CONFIG_CLOSURE_DEBUG
+ cl->waiting_on = f;
+#endif
+}
+
+static inline void __closure_end_sleep(struct closure *cl)
+{
+ __set_current_state(TASK_RUNNING);
+
+ if (atomic_read(&cl->remaining) & CLOSURE_SLEEPING)
+ atomic_sub(CLOSURE_SLEEPING, &cl->remaining);
+}
+
+static inline void __closure_start_sleep(struct closure *cl)
+{
+ closure_set_ip(cl);
+ cl->task = current;
+ set_current_state(TASK_UNINTERRUPTIBLE);
+
+ if (!(atomic_read(&cl->remaining) & CLOSURE_SLEEPING))
+ atomic_add(CLOSURE_SLEEPING, &cl->remaining);
+}
+
+static inline void closure_set_stopped(struct closure *cl)
+{
+ atomic_sub(CLOSURE_RUNNING, &cl->remaining);
+}
+
+static inline void set_closure_fn(struct closure *cl, closure_fn *fn,
+ struct workqueue_struct *wq)
+{
+ BUG_ON(object_is_on_stack(cl));
+ closure_set_ip(cl);
+ cl->fn = fn;
+ cl->wq = wq;
+ /* between atomic_dec() in closure_put() */
+ smp_mb__before_atomic_dec();
+}
+
+static inline void closure_queue(struct closure *cl)
+{
+ struct workqueue_struct *wq = cl->wq;
+ if (wq) {
+ INIT_WORK(&cl->work, cl->work.func);
+ BUG_ON(!queue_work(wq, &cl->work));
+ } else
+ cl->fn(cl);
+}
+
+/**
+ * closure_get - increment a closure's refcount
+ */
+static inline void closure_get(struct closure *cl)
+{
+#ifdef CONFIG_CLOSURE_DEBUG
+ BUG_ON((atomic_inc_return(&cl->remaining) &
+ CLOSURE_REMAINING_MASK) <= 1);
+#else
+ atomic_inc(&cl->remaining);
+#endif
+}
+
+/**
+ * closure_init - Initialize a closure, setting the refcount to 1
+ * @cl: closure to initialize
+ * @parent: parent of the new closure. cl will take a refcount on it for its
+ * lifetime; may be NULL.
+ */
+static inline void closure_init(struct closure *cl, struct closure *parent)
+{
+ memset(cl, 0, sizeof(struct closure));
+ cl->parent = parent;
+ if (parent)
+ closure_get(parent);
+
+ atomic_set(&cl->remaining, CLOSURE_REMAINING_INITIALIZER);
+
+ closure_debug_create(cl);
+ closure_set_ip(cl);
+}
+
+static inline void closure_init_stack(struct closure *cl)
+{
+ memset(cl, 0, sizeof(struct closure));
+ atomic_set(&cl->remaining, CLOSURE_REMAINING_INITIALIZER|CLOSURE_STACK);
+}
+
+/**
+ * closure_wake_up - wake up all closures on a wait list.
+ */
+static inline void closure_wake_up(struct closure_waitlist *list)
+{
+ smp_mb();
+ __closure_wake_up(list);
+}
+
+/**
+ * closure_wait_event - wait on arbitrary event
+ *
+ * Analogous to wait_event() but for closures.
+ *
+ * The loop is oddly structured so as to avoid a race; we must check the
+ * condition again after we've added ourself to the waitlist. We know if we were
+ * already on the waitlist because closure_wait() returns false; thus, we only
+ * schedule or break if closure_wait() returns false. If it returns true, we
+ * just loop again - rechecking the condition.
+ *
+ * The __closure_wake_up() is necessary because we may race with the event
+ * becoming true; i.e. we see event false -> wait -> recheck condition, but the
+ * thread that made the event true may have called closure_wake_up() before we
+ * added ourself to the wait list.
+ *
+ * We have to call closure_sync() at the end instead of just
+ * __closure_end_sleep() because a different thread might've called
+ * closure_wake_up() before us and gotten preempted before they dropped the
+ * refcount on our closure. If this was a stack allocated closure, that would be
+ * bad.
+ */
+#define closure_wait_event(list, cl, condition) \
+({ \
+ typeof(condition) ret; \
+ \
+ while (1) { \
+ ret = (condition); \
+ if (ret) { \
+ __closure_wake_up(list); \
+ closure_sync(cl); \
+ break; \
+ } \
+ \
+ __closure_start_sleep(cl); \
+ \
+ if (!closure_wait(list, cl)) \
+ schedule(); \
+ } \
+ \
+ ret; \
+})
+
+/**
+ * continue_at - jump to another function with barrier
+ *
+ * After @cl is no longer waiting on anything (i.e. all outstanding refs have
+ * been dropped with closure_put()), it will resume execution at @fn running out
+ * of @wq (or, if @wq is NULL, @fn will be called by closure_put() directly).
+ *
+ * NOTE: This macro expands to a return in the calling function!
+ *
+ * This is because after calling continue_at() you no longer have a ref on @cl,
+ * and whatever @cl owns may be freed out from under you - a running closure fn
+ * has a ref on its own closure which continue_at() drops.
+ */
+#define continue_at(_cl, _fn, _wq) \
+do { \
+ set_closure_fn(_cl, _fn, _wq); \
+ closure_sub(_cl, CLOSURE_RUNNING + 1); \
+ return; \
+} while (0)
+
+/**
+ * closure_return - finish execution of a closure
+ *
+ * This is used to indicate that @cl is finished: when all outstanding refs on
+ * @cl have been dropped @cl's ref on its parent closure (as passed to
+ * closure_init()) will be dropped, if one was specified - thus this can be
+ * thought of as returning to the parent closure.
+ */
+#define closure_return(_cl) continue_at((_cl), NULL, NULL)
+
+/**
+ * continue_at_nobarrier - jump to another function without barrier
+ *
+ * Causes @fn to be executed out of @cl, in @wq context (or called directly if
+ * @wq is NULL).
+ *
+ * NOTE: like continue_at(), this macro expands to a return in the caller!
+ *
+ * The ref the caller of continue_at_nobarrier() had on @cl is now owned by @fn,
+ * thus it's not safe to touch anything protected by @cl after a
+ * continue_at_nobarrier().
+ */
+#define continue_at_nobarrier(_cl, _fn, _wq) \
+do { \
+ set_closure_fn(_cl, _fn, _wq); \
+ closure_queue(_cl); \
+ return; \
+} while (0)
+
+/**
+ * closure_return - finish execution of a closure, with destructor
+ *
+ * Works like closure_return(), except @destructor will be called when all
+ * outstanding refs on @cl have been dropped; @destructor may be used to safely
+ * free the memory occupied by @cl, and it is called with the ref on the parent
+ * closure still held - so @destructor could safely return an item to a
+ * freelist protected by @cl's parent.
+ */
+#define closure_return_with_destructor(_cl, _destructor) \
+do { \
+ set_closure_fn(_cl, _destructor, NULL); \
+ closure_sub(_cl, CLOSURE_RUNNING - CLOSURE_DESTRUCTOR + 1); \
+ return; \
+} while (0)
+
+/**
+ * closure_call - execute @fn out of a new, uninitialized closure
+ *
+ * Typically used when running out of one closure, and we want to run @fn
+ * asynchronously out of a new closure - @parent will then wait for @cl to
+ * finish.
+ */
+static inline void closure_call(struct closure *cl, closure_fn fn,
+ struct workqueue_struct *wq,
+ struct closure *parent)
+{
+ closure_init(cl, parent);
+ continue_at_nobarrier(cl, fn, wq);
+}
+
+#endif /* _LINUX_CLOSURE_H */
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index db25707aa4..0d1dbbf07a 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1240,6 +1240,14 @@ config DEBUG_BLOCK_EXT_DEVT

Say N if you are unsure.

+config CLOSURE_DEBUG
+ bool "Debug closures"
+ select DEBUG_FS
+ ---help---
+ Keeps all active closures in a linked list and provides a debugfs
+ interface to list them, which makes it possible to see asynchronous
+ operations that get stuck.
+
config NOTIFIER_ERROR_INJECTION
tristate "Notifier error injection"
depends on DEBUG_KERNEL
diff --git a/lib/Makefile b/lib/Makefile
index a459c31e8c..907c11b788 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -26,7 +26,7 @@ obj-y += bcd.o div64.o sort.o parser.o halfmd4.o debug_locks.o random32.o \
bust_spinlocks.o hexdump.o kasprintf.o bitmap.o scatterlist.o \
gcd.o lcm.o list_sort.o uuid.o flex_array.o iovec.o clz_ctz.o \
bsearch.o find_last_bit.o find_next_bit.o llist.o memweight.o kfifo.o \
- percpu-refcount.o percpu_ida.o
+ percpu-refcount.o percpu_ida.o closure.o
obj-y += string_helpers.o
obj-$(CONFIG_TEST_STRING_HELPERS) += test-string_helpers.o
obj-y += kstrtox.o
diff --git a/lib/closure.c b/lib/closure.c
new file mode 100644
index 0000000000..10ec8a1711
--- /dev/null
+++ b/lib/closure.c
@@ -0,0 +1,218 @@
+/*
+ * Asynchronous refcounty things
+ *
+ * Copyright 2010, 2011 Kent Overstreet <kent.overstreet@gmail.com>
+ * Copyright 2012 Google, Inc.
+ */
+
+#include <linux/closure.h>
+#include <linux/debugfs.h>
+#include <linux/seq_file.h>
+
+static inline void closure_put_after_sub(struct closure *cl, int flags)
+{
+ int r = flags & CLOSURE_REMAINING_MASK;
+
+ BUG_ON(flags & CLOSURE_GUARD_MASK);
+ BUG_ON(!r && (flags & ~CLOSURE_DESTRUCTOR));
+
+ /* Must deliver precisely one wakeup */
+ if (r == 1 && (flags & CLOSURE_SLEEPING))
+ wake_up_process(cl->task);
+
+ if (!r) {
+ if (cl->fn && !(flags & CLOSURE_DESTRUCTOR)) {
+ atomic_set(&cl->remaining,
+ CLOSURE_REMAINING_INITIALIZER);
+ closure_queue(cl);
+ } else {
+ struct closure *parent = cl->parent;
+ closure_fn *destructor = cl->fn;
+
+ closure_debug_destroy(cl);
+
+ if (destructor)
+ destructor(cl);
+
+ if (parent)
+ closure_put(parent);
+ }
+ }
+}
+
+/* For clearing flags with the same atomic op as a put */
+void closure_sub(struct closure *cl, int v)
+{
+ closure_put_after_sub(cl, atomic_sub_return(v, &cl->remaining));
+}
+EXPORT_SYMBOL(closure_sub);
+
+/**
+ * closure_put - decrement a closure's refcount
+ */
+void closure_put(struct closure *cl)
+{
+ closure_put_after_sub(cl, atomic_dec_return(&cl->remaining));
+}
+EXPORT_SYMBOL(closure_put);
+
+/**
+ * closure_wake_up - wake up all closures on a wait list, without memory barrier
+ */
+void __closure_wake_up(struct closure_waitlist *wait_list)
+{
+ struct llist_node *list;
+ struct closure *cl;
+ struct llist_node *reverse = NULL;
+
+ list = llist_del_all(&wait_list->list);
+
+ /* We first reverse the list to preserve FIFO ordering and fairness */
+
+ while (list) {
+ struct llist_node *t = list;
+ list = llist_next(list);
+
+ t->next = reverse;
+ reverse = t;
+ }
+
+ /* Then do the wakeups */
+
+ while (reverse) {
+ cl = container_of(reverse, struct closure, list);
+ reverse = llist_next(reverse);
+
+ closure_set_waiting(cl, 0);
+ closure_sub(cl, CLOSURE_WAITING + 1);
+ }
+}
+EXPORT_SYMBOL(__closure_wake_up);
+
+/**
+ * closure_wait - add a closure to a waitlist
+ *
+ * @waitlist will own a ref on @cl, which will be released when
+ * closure_wake_up() is called on @waitlist.
+ *
+ */
+bool closure_wait(struct closure_waitlist *waitlist, struct closure *cl)
+{
+ if (atomic_read(&cl->remaining) & CLOSURE_WAITING)
+ return false;
+
+ closure_set_waiting(cl, _RET_IP_);
+ atomic_add(CLOSURE_WAITING + 1, &cl->remaining);
+ llist_add(&cl->list, &waitlist->list);
+
+ return true;
+}
+EXPORT_SYMBOL(closure_wait);
+
+/**
+ * closure_sync - sleep until a closure a closure has nothing left to wait on
+ *
+ * Sleeps until the refcount hits 1 - the thread that's running the closure owns
+ * the last refcount.
+ */
+void closure_sync(struct closure *cl)
+{
+ while (1) {
+ __closure_start_sleep(cl);
+ closure_set_ret_ip(cl);
+
+ if ((atomic_read(&cl->remaining) &
+ CLOSURE_REMAINING_MASK) == 1)
+ break;
+
+ schedule();
+ }
+
+ __closure_end_sleep(cl);
+}
+EXPORT_SYMBOL(closure_sync);
+
+#ifdef CONFIG_CLOSURE_DEBUG
+
+static LIST_HEAD(closure_list);
+static DEFINE_SPINLOCK(closure_list_lock);
+
+void closure_debug_create(struct closure *cl)
+{
+ unsigned long flags;
+
+ BUG_ON(cl->magic == CLOSURE_MAGIC_ALIVE);
+ cl->magic = CLOSURE_MAGIC_ALIVE;
+
+ spin_lock_irqsave(&closure_list_lock, flags);
+ list_add(&cl->all, &closure_list);
+ spin_unlock_irqrestore(&closure_list_lock, flags);
+}
+EXPORT_SYMBOL(closure_debug_create);
+
+void closure_debug_destroy(struct closure *cl)
+{
+ unsigned long flags;
+
+ BUG_ON(cl->magic != CLOSURE_MAGIC_ALIVE);
+ cl->magic = CLOSURE_MAGIC_DEAD;
+
+ spin_lock_irqsave(&closure_list_lock, flags);
+ list_del(&cl->all);
+ spin_unlock_irqrestore(&closure_list_lock, flags);
+}
+EXPORT_SYMBOL(closure_debug_destroy);
+
+static struct dentry *debug;
+
+#define work_data_bits(work) ((unsigned long *)(&(work)->data))
+
+static int debug_seq_show(struct seq_file *f, void *data)
+{
+ struct closure *cl;
+ spin_lock_irq(&closure_list_lock);
+
+ list_for_each_entry(cl, &closure_list, all) {
+ int r = atomic_read(&cl->remaining);
+
+ seq_printf(f, "%p: %pF -> %pf p %p r %i ",
+ cl, (void *) cl->ip, cl->fn, cl->parent,
+ r & CLOSURE_REMAINING_MASK);
+
+ seq_printf(f, "%s%s%s%s\n",
+ test_bit(WORK_STRUCT_PENDING,
+ work_data_bits(&cl->work)) ? "Q" : "",
+ r & CLOSURE_RUNNING ? "R" : "",
+ r & CLOSURE_STACK ? "S" : "",
+ r & CLOSURE_SLEEPING ? "Sl" : "");
+
+ if (r & CLOSURE_WAITING)
+ seq_printf(f, " W %pF\n",
+ (void *) cl->waiting_on);
+
+ seq_printf(f, "\n");
+ }
+
+ spin_unlock_irq(&closure_list_lock);
+ return 0;
+}
+
+static int debug_seq_open(struct inode *inode, struct file *file)
+{
+ return single_open(file, debug_seq_show, NULL);
+}
+
+static const struct file_operations debug_ops = {
+ .open = debug_seq_open,
+ .read = seq_read,
+ .release = single_release
+};
+
+static int __init closure_debug_init(void)
+{
+ debug = debugfs_create_file("closures", 0400, NULL, NULL, &debug_ops);
+ return 0;
+}
+late_initcall(closure_debug_init);
+
+#endif
--
1.8.5.1