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// SPDX-License-Identifier: GPL-2.0
/*
* Asynchronous refcounty things
*
* Copyright 2010, 2011 Kent Overstreet <kent.overstreet@gmail.com>
* Copyright 2012 Google, Inc.
*/
#include "closure.h"
#include <linux/debugfs.h>
#include <linux/export.h>
#include <linux/rcupdate.h>
#include <linux/seq_file.h>
#include <linux/sched/debug.h>
static void closure_val_checks(struct closure *cl, unsigned new, int d)
{
unsigned count = new & CLOSURE_REMAINING_MASK;
if (WARN(new & CLOSURE_GUARD_MASK,
"closure %ps has guard bits set: %x (%u), delta %i",
cl->fn,
new, (unsigned) __fls(new & CLOSURE_GUARD_MASK), d))
new &= ~CLOSURE_GUARD_MASK;
WARN(!count && (new & ~(CLOSURE_DESTRUCTOR|CLOSURE_SLEEPING)),
"closure %ps ref hit 0 with incorrect flags set: %x (%u)",
cl->fn,
new, (unsigned) __fls(new));
}
enum new_closure_state {
CLOSURE_normal_put,
CLOSURE_requeue,
CLOSURE_done,
};
/* For clearing flags with the same atomic op as a put */
void bch2_closure_sub(struct closure *cl, int v)
{
enum new_closure_state s;
struct task_struct *sleeper;
/* rcu_read_lock, atomic_read_acquire() are both for cl->sleeper: */
guard(rcu)();
int old = atomic_read_acquire(&cl->remaining), new;
do {
new = old - v;
if (new & CLOSURE_REMAINING_MASK) {
s = CLOSURE_normal_put;
} else {
if ((cl->fn || (new & CLOSURE_SLEEPING)) &&
!(new & CLOSURE_DESTRUCTOR)) {
s = CLOSURE_requeue;
new += CLOSURE_REMAINING_INITIALIZER;
} else
s = CLOSURE_done;
sleeper = new & CLOSURE_SLEEPING ? cl->sleeper : NULL;
new &= ~CLOSURE_SLEEPING;
}
closure_val_checks(cl, new, -v);
} while (!atomic_try_cmpxchg_release(&cl->remaining, &old, new));
if (s == CLOSURE_normal_put)
return;
if (sleeper) {
smp_mb();
wake_up_process(sleeper);
return;
}
if (s == CLOSURE_requeue) {
closure_queue(cl);
} else {
struct closure *parent = cl->parent;
closure_fn *destructor = cl->fn;
closure_debug_destroy(cl);
if (destructor)
destructor(&cl->work);
if (parent)
closure_put(parent);
}
}
/*
* closure_wake_up - wake up all closures on a wait list, without memory barrier
*/
void __bch2_closure_wake_up(struct closure_waitlist *wait_list)
{
struct llist_node *list;
struct closure *cl, *t;
struct llist_node *reverse = NULL;
list = llist_del_all(&wait_list->list);
/* We first reverse the list to preserve FIFO ordering and fairness */
reverse = llist_reverse_order(list);
/* Then do the wakeups */
llist_for_each_entry_safe(cl, t, reverse, list) {
closure_set_waiting(cl, 0);
bch2_closure_sub(cl, CLOSURE_WAITING + 1);
}
}
/**
* 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.
* @cl: closure pointer.
*
*/
bool bch2_closure_wait(struct closure_waitlist *waitlist, struct closure *cl)
{
if (atomic_read(&cl->remaining) & CLOSURE_WAITING)
return false;
closure_set_waiting(cl, _RET_IP_);
unsigned r = atomic_add_return(CLOSURE_WAITING + 1, &cl->remaining);
closure_val_checks(cl, r, CLOSURE_WAITING + 1);
llist_add(&cl->list, &waitlist->list);
return true;
}
void __sched __bch2_closure_sync(struct closure *cl)
{
cl->sleeper = current;
bch2_closure_sub(cl,
CLOSURE_REMAINING_INITIALIZER -
CLOSURE_SLEEPING);
while (1) {
set_current_state(TASK_UNINTERRUPTIBLE);
if (!(atomic_read(&cl->remaining) & CLOSURE_SLEEPING))
break;
schedule();
}
__set_current_state(TASK_RUNNING);
}
/*
* closure_return_sync - finish running a closure, synchronously (i.e. waiting
* for outstanding get()s to finish) and returning once closure refcount is 0.
*
* Unlike closure_sync() this doesn't reinit the ref to 1; subsequent
* closure_get_not_zero() calls will fail.
*/
void __sched bch2_closure_return_sync(struct closure *cl)
{
cl->sleeper = current;
bch2_closure_sub(cl,
CLOSURE_REMAINING_INITIALIZER -
CLOSURE_DESTRUCTOR -
CLOSURE_SLEEPING);
while (1) {
set_current_state(TASK_UNINTERRUPTIBLE);
if (!(atomic_read(&cl->remaining) & CLOSURE_SLEEPING))
break;
schedule();
}
__set_current_state(TASK_RUNNING);
if (cl->parent)
closure_put(cl->parent);
}
int __sched __bch2_closure_sync_timeout(struct closure *cl, unsigned long timeout)
{
int ret = 0;
cl->sleeper = current;
bch2_closure_sub(cl,
CLOSURE_REMAINING_INITIALIZER -
CLOSURE_SLEEPING);
while (1) {
set_current_state(TASK_UNINTERRUPTIBLE);
/*
* Carefully undo the continue_at() - but only if it
* hasn't completed, i.e. the final closure_put() hasn't
* happened yet:
*/
unsigned old = atomic_read(&cl->remaining), new;
if (!(old & CLOSURE_SLEEPING))
goto success;
if (!timeout) {
do {
if (!(old & CLOSURE_SLEEPING))
goto success;
new = old + CLOSURE_REMAINING_INITIALIZER - CLOSURE_SLEEPING;
closure_val_checks(cl, new, CLOSURE_REMAINING_INITIALIZER - CLOSURE_SLEEPING);
} while (!atomic_try_cmpxchg(&cl->remaining, &old, new));
ret = -ETIME;
break;
}
timeout = schedule_timeout(timeout);
}
success:
__set_current_state(TASK_RUNNING);
return ret;
}
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