#include <linux/preempt.h>
#include <linux/rcupdate.h>
#include <linux/sched.h>
+#include <linux/sched/clock.h>
#include <linux/sched/rt.h>
#include <linux/six.h>
+#include <linux/slab.h>
#ifdef DEBUG
#define EBUG_ON(cond) BUG_ON(cond)
#define EBUG_ON(cond) do {} while (0)
#endif
-#define six_acquire(l, t) lock_acquire(l, 0, t, 0, 0, NULL, _RET_IP_)
+#define six_acquire(l, t, r) lock_acquire(l, 0, t, r, 1, NULL, _RET_IP_)
#define six_release(l) lock_release(l, _RET_IP_)
+static void do_six_unlock_type(struct six_lock *lock, enum six_lock_type type);
+
struct six_lock_vals {
/* Value we add to the lock in order to take the lock: */
u64 lock_val;
}
static inline void six_set_owner(struct six_lock *lock, enum six_lock_type type,
- union six_lock_state old)
+ union six_lock_state old,
+ struct task_struct *owner)
{
if (type != SIX_LOCK_intent)
return;
if (!old.intent_lock) {
EBUG_ON(lock->owner);
- lock->owner = current;
+ lock->owner = owner;
} else {
EBUG_ON(lock->owner != current);
}
return read_count;
}
-struct six_lock_waiter {
- struct list_head list;
- struct task_struct *task;
-};
-
/* This is probably up there with the more evil things I've done */
#define waitlist_bitnr(id) ilog2((((union six_lock_state) { .waiters = 1 << (id) }).l))
-static inline void six_lock_wakeup(struct six_lock *lock,
- union six_lock_state state,
- unsigned waitlist_id)
-{
- if (waitlist_id == SIX_LOCK_write) {
- if (state.write_locking && !state.read_lock) {
- struct task_struct *p = READ_ONCE(lock->owner);
- if (p)
- wake_up_process(p);
- }
- } else {
- struct list_head *wait_list = &lock->wait_list[waitlist_id];
- struct six_lock_waiter *w, *next;
-
- if (!(state.waiters & (1 << waitlist_id)))
- return;
-
- clear_bit(waitlist_bitnr(waitlist_id),
- (unsigned long *) &lock->state.v);
-
- raw_spin_lock(&lock->wait_lock);
-
- list_for_each_entry_safe(w, next, wait_list, list) {
- list_del_init(&w->list);
-
- if (wake_up_process(w->task) &&
- waitlist_id != SIX_LOCK_read) {
- if (!list_empty(wait_list))
- set_bit(waitlist_bitnr(waitlist_id),
- (unsigned long *) &lock->state.v);
- break;
- }
- }
-
- raw_spin_unlock(&lock->wait_lock);
- }
-}
-
-static __always_inline bool do_six_trylock_type(struct six_lock *lock,
- enum six_lock_type type,
- bool try)
+static int __do_six_trylock_type(struct six_lock *lock,
+ enum six_lock_type type,
+ struct task_struct *task,
+ bool try)
{
const struct six_lock_vals l[] = LOCK_VALS;
union six_lock_state old, new;
- bool ret;
+ int ret;
u64 v;
- EBUG_ON(type == SIX_LOCK_write && lock->owner != current);
+ EBUG_ON(type == SIX_LOCK_write && lock->owner != task);
EBUG_ON(type == SIX_LOCK_write && (lock->state.seq & 1));
-
EBUG_ON(type == SIX_LOCK_write && (try != !(lock->state.write_locking)));
/*
*/
if (type == SIX_LOCK_read && lock->readers) {
-retry:
preempt_disable();
this_cpu_inc(*lock->readers); /* signal that we own lock */
* lock, issue a wakeup because we might have caused a
* spurious trylock failure:
*/
- if (old.write_locking) {
- struct task_struct *p = READ_ONCE(lock->owner);
-
- if (p)
- wake_up_process(p);
- }
-
- /*
- * If we failed from the lock path and the waiting bit wasn't
- * set, set it:
- */
- if (!try && !ret) {
- v = old.v;
-
- do {
- new.v = old.v = v;
-
- if (!(old.v & l[type].lock_fail))
- goto retry;
-
- if (new.waiters & (1 << type))
- break;
-
- new.waiters |= 1 << type;
- } while ((v = atomic64_cmpxchg(&lock->state.counter,
- old.v, new.v)) != old.v);
- }
+ if (old.write_locking)
+ ret = -1 - SIX_LOCK_write;
} else if (type == SIX_LOCK_write && lock->readers) {
if (try) {
atomic64_add(__SIX_VAL(write_locking, 1),
if (ret || try)
v -= __SIX_VAL(write_locking, 1);
+ if (!ret && !try && !(lock->state.waiters & (1 << SIX_LOCK_write)))
+ v += __SIX_VAL(waiters, 1 << SIX_LOCK_write);
+
if (try && !ret) {
old.v = atomic64_add_return(v, &lock->state.counter);
- six_lock_wakeup(lock, old, SIX_LOCK_read);
+ if (old.waiters & (1 << SIX_LOCK_read))
+ ret = -1 - SIX_LOCK_read;
} else {
atomic64_add(v, &lock->state.counter);
}
if (type == SIX_LOCK_write)
new.write_locking = 0;
- } else if (!try && type != SIX_LOCK_write &&
- !(new.waiters & (1 << type)))
+ } else if (!try && !(new.waiters & (1 << type)))
new.waiters |= 1 << type;
else
break; /* waiting bit already set */
old.v, new.v)) != old.v);
ret = !(old.v & l[type].lock_fail);
+
+ EBUG_ON(ret && !(lock->state.v & l[type].held_mask));
}
- if (ret)
- six_set_owner(lock, type, old);
+ if (ret > 0)
+ six_set_owner(lock, type, old, task);
- EBUG_ON(ret && !(lock->state.v & l[type].held_mask));
- EBUG_ON(type == SIX_LOCK_write && (try || ret) && (lock->state.write_locking));
+ EBUG_ON(type == SIX_LOCK_write && (try || ret > 0) && (lock->state.write_locking));
return ret;
}
+static inline void __six_lock_wakeup(struct six_lock *lock, enum six_lock_type lock_type)
+{
+ struct six_lock_waiter *w, *next;
+ struct task_struct *task;
+ bool saw_one;
+ int ret;
+again:
+ ret = 0;
+ saw_one = false;
+ raw_spin_lock(&lock->wait_lock);
+
+ list_for_each_entry_safe(w, next, &lock->wait_list, list) {
+ if (w->lock_want != lock_type)
+ continue;
+
+ if (saw_one && lock_type != SIX_LOCK_read)
+ goto unlock;
+ saw_one = true;
+
+ ret = __do_six_trylock_type(lock, lock_type, w->task, false);
+ if (ret <= 0)
+ goto unlock;
+
+ __list_del(w->list.prev, w->list.next);
+ task = w->task;
+ /*
+ * Do no writes to @w besides setting lock_acquired - otherwise
+ * we would need a memory barrier:
+ */
+ barrier();
+ w->lock_acquired = true;
+ wake_up_process(task);
+ }
+
+ clear_bit(waitlist_bitnr(lock_type), (unsigned long *) &lock->state.v);
+unlock:
+ raw_spin_unlock(&lock->wait_lock);
+
+ if (ret < 0) {
+ lock_type = -ret - 1;
+ goto again;
+ }
+}
+
+static inline void six_lock_wakeup(struct six_lock *lock,
+ union six_lock_state state,
+ enum six_lock_type lock_type)
+{
+ if (lock_type == SIX_LOCK_write && state.read_lock)
+ return;
+
+ if (!(state.waiters & (1 << lock_type)))
+ return;
+
+ __six_lock_wakeup(lock, lock_type);
+}
+
+static bool do_six_trylock_type(struct six_lock *lock,
+ enum six_lock_type type,
+ bool try)
+{
+ int ret;
+
+ ret = __do_six_trylock_type(lock, type, current, try);
+ if (ret < 0)
+ __six_lock_wakeup(lock, -ret - 1);
+
+ return ret > 0;
+}
+
__always_inline __flatten
static bool __six_trylock_type(struct six_lock *lock, enum six_lock_type type)
{
return false;
if (type != SIX_LOCK_write)
- six_acquire(&lock->dep_map, 1);
+ six_acquire(&lock->dep_map, 1, type == SIX_LOCK_read);
return true;
}
* Similar to the lock path, we may have caused a spurious write
* lock fail and need to issue a wakeup:
*/
- if (old.write_locking) {
- struct task_struct *p = READ_ONCE(lock->owner);
+ if (old.write_locking)
+ six_lock_wakeup(lock, old, SIX_LOCK_write);
- if (p)
- wake_up_process(p);
- }
+ if (ret)
+ six_acquire(&lock->dep_map, 1, type == SIX_LOCK_read);
return ret;
}
old.v,
old.v + l[type].lock_val)) != old.v);
- six_set_owner(lock, type, old);
+ six_set_owner(lock, type, old, current);
if (type != SIX_LOCK_write)
- six_acquire(&lock->dep_map, 1);
+ six_acquire(&lock->dep_map, 1, type == SIX_LOCK_read);
return true;
}
#ifdef CONFIG_LOCK_SPIN_ON_OWNER
-static inline int six_can_spin_on_owner(struct six_lock *lock)
+static inline bool six_optimistic_spin(struct six_lock *lock,
+ struct six_lock_waiter *wait)
{
- struct task_struct *owner;
- int retval = 1;
+ struct task_struct *owner, *task = current;
- if (need_resched())
- return 0;
+ switch (wait->lock_want) {
+ case SIX_LOCK_read:
+ break;
+ case SIX_LOCK_intent:
+ if (lock->wait_list.next != &wait->list)
+ return false;
+ break;
+ case SIX_LOCK_write:
+ return false;
+ }
rcu_read_lock();
owner = READ_ONCE(lock->owner);
- if (owner)
- retval = owner->on_cpu;
- rcu_read_unlock();
- /*
- * if lock->owner is not set, the mutex owner may have just acquired
- * it and not set the owner yet or the mutex has been released.
- */
- return retval;
-}
-static inline bool six_spin_on_owner(struct six_lock *lock,
- struct task_struct *owner)
-{
- bool ret = true;
-
- rcu_read_lock();
- while (lock->owner == owner) {
+ while (owner && lock->owner == owner) {
/*
* Ensure we emit the owner->on_cpu, dereference _after_
* checking lock->owner still matches owner. If that fails,
*/
barrier();
- if (!owner->on_cpu || need_resched()) {
- ret = false;
- break;
- }
-
- cpu_relax();
- }
- rcu_read_unlock();
-
- return ret;
-}
-
-static inline bool six_optimistic_spin(struct six_lock *lock, enum six_lock_type type)
-{
- struct task_struct *task = current;
-
- if (type == SIX_LOCK_write)
- return false;
-
- preempt_disable();
- if (!six_can_spin_on_owner(lock))
- goto fail;
-
- if (!osq_lock(&lock->osq))
- goto fail;
-
- while (1) {
- struct task_struct *owner;
-
/*
- * If there's an owner, wait for it to either
- * release the lock or go to sleep.
- */
- owner = READ_ONCE(lock->owner);
- if (owner && !six_spin_on_owner(lock, owner))
- break;
-
- if (do_six_trylock_type(lock, type, false)) {
- osq_unlock(&lock->osq);
- preempt_enable();
- return true;
- }
-
- /*
- * When there's no owner, we might have preempted between the
- * owner acquiring the lock and setting the owner field. If
- * we're an RT task that will live-lock because we won't let
+ * If we're an RT task that will live-lock because we won't let
* the owner complete.
*/
- if (!owner && (need_resched() || rt_task(task)))
+ if (wait->lock_acquired ||
+ !owner->on_cpu ||
+ rt_task(task) ||
+ need_resched())
break;
- /*
- * The cpu_relax() call is a compiler barrier which forces
- * everything in this loop to be re-loaded. We don't need
- * memory barriers as we'll eventually observe the right
- * values at the cost of a few extra spins.
- */
cpu_relax();
}
+ rcu_read_unlock();
- osq_unlock(&lock->osq);
-fail:
- preempt_enable();
-
- /*
- * If we fell out of the spin path because of need_resched(),
- * reschedule now, before we try-lock again. This avoids getting
- * scheduled out right after we obtained the lock.
- */
- if (need_resched())
- schedule();
-
- return false;
+ return wait->lock_acquired;
}
#else /* CONFIG_LOCK_SPIN_ON_OWNER */
-static inline bool six_optimistic_spin(struct six_lock *lock, enum six_lock_type type)
+static inline bool six_optimistic_spin(struct six_lock *lock,
+ struct six_lock_waiter *wait)
{
return false;
}
noinline
static int __six_lock_type_slowpath(struct six_lock *lock, enum six_lock_type type,
+ struct six_lock_waiter *wait,
six_lock_should_sleep_fn should_sleep_fn, void *p)
{
union six_lock_state old;
- struct six_lock_waiter wait;
int ret = 0;
if (type == SIX_LOCK_write) {
smp_mb__after_atomic();
}
- ret = should_sleep_fn ? should_sleep_fn(lock, p) : 0;
- if (ret)
- goto out_before_sleep;
+ lock_contended(&lock->dep_map, _RET_IP_);
- if (six_optimistic_spin(lock, type))
- goto out_before_sleep;
+ wait->task = current;
+ wait->lock_want = type;
+ wait->lock_acquired = false;
- lock_contended(&lock->dep_map, _RET_IP_);
+ raw_spin_lock(&lock->wait_lock);
+ if (!(lock->state.waiters & (1 << type)))
+ set_bit(waitlist_bitnr(type), (unsigned long *) &lock->state.v);
+ /*
+ * Retry taking the lock after taking waitlist lock, have raced with an
+ * unlock:
+ */
+ ret = __do_six_trylock_type(lock, type, current, false);
+ if (ret <= 0) {
+ wait->start_time = local_clock();
+
+ if (!list_empty(&lock->wait_list)) {
+ struct six_lock_waiter *last =
+ list_last_entry(&lock->wait_list,
+ struct six_lock_waiter, list);
+
+ if (time_before_eq64(wait->start_time, last->start_time))
+ wait->start_time = last->start_time + 1;
+ }
+
+ list_add_tail(&wait->list, &lock->wait_list);
+ }
+ raw_spin_unlock(&lock->wait_lock);
+
+ if (unlikely(ret > 0)) {
+ ret = 0;
+ goto out;
+ }
- INIT_LIST_HEAD(&wait.list);
- wait.task = current;
+ if (unlikely(ret < 0)) {
+ __six_lock_wakeup(lock, -ret - 1);
+ ret = 0;
+ }
+
+ if (six_optimistic_spin(lock, wait))
+ goto out;
while (1) {
set_current_state(TASK_UNINTERRUPTIBLE);
- if (type == SIX_LOCK_write)
- EBUG_ON(lock->owner != current);
- else if (list_empty_careful(&wait.list)) {
- raw_spin_lock(&lock->wait_lock);
- list_add_tail(&wait.list, &lock->wait_list[type]);
- raw_spin_unlock(&lock->wait_lock);
- }
- if (do_six_trylock_type(lock, type, false))
+ if (wait->lock_acquired)
break;
ret = should_sleep_fn ? should_sleep_fn(lock, p) : 0;
- if (ret)
+ if (unlikely(ret)) {
+ raw_spin_lock(&lock->wait_lock);
+ if (!wait->lock_acquired)
+ list_del(&wait->list);
+ raw_spin_unlock(&lock->wait_lock);
+
+ if (wait->lock_acquired)
+ do_six_unlock_type(lock, type);
break;
+ }
schedule();
}
__set_current_state(TASK_RUNNING);
-
- if (!list_empty_careful(&wait.list)) {
- raw_spin_lock(&lock->wait_lock);
- list_del_init(&wait.list);
- raw_spin_unlock(&lock->wait_lock);
- }
-out_before_sleep:
- if (ret && type == SIX_LOCK_write) {
+out:
+ if (ret && type == SIX_LOCK_write && lock->state.write_locking) {
old.v = atomic64_sub_return(__SIX_VAL(write_locking, 1),
&lock->state.counter);
six_lock_wakeup(lock, old, SIX_LOCK_read);
return ret;
}
-__always_inline
-static int __six_lock_type(struct six_lock *lock, enum six_lock_type type,
- six_lock_should_sleep_fn should_sleep_fn, void *p)
+__always_inline __flatten
+static int __six_lock_type_waiter(struct six_lock *lock, enum six_lock_type type,
+ struct six_lock_waiter *wait,
+ six_lock_should_sleep_fn should_sleep_fn, void *p)
{
int ret;
+ wait->start_time = 0;
+
if (type != SIX_LOCK_write)
- six_acquire(&lock->dep_map, 0);
+ six_acquire(&lock->dep_map, 0, type == SIX_LOCK_read);
ret = do_six_trylock_type(lock, type, true) ? 0
- : __six_lock_type_slowpath(lock, type, should_sleep_fn, p);
+ : __six_lock_type_slowpath(lock, type, wait, should_sleep_fn, p);
if (ret && type != SIX_LOCK_write)
six_release(&lock->dep_map);
return ret;
}
+__always_inline
+static int __six_lock_type(struct six_lock *lock, enum six_lock_type type,
+ six_lock_should_sleep_fn should_sleep_fn, void *p)
+{
+ struct six_lock_waiter wait;
+
+ return __six_lock_type_waiter(lock, type, &wait, should_sleep_fn, p);
+}
+
__always_inline __flatten
-static void __six_unlock_type(struct six_lock *lock, enum six_lock_type type)
+static void do_six_unlock_type(struct six_lock *lock, enum six_lock_type type)
{
const struct six_lock_vals l[] = LOCK_VALS;
union six_lock_state state;
- EBUG_ON(type == SIX_LOCK_write &&
- !(lock->state.v & __SIX_LOCK_HELD_intent));
-
- if (type != SIX_LOCK_write)
- six_release(&lock->dep_map);
-
- if (type == SIX_LOCK_intent) {
- EBUG_ON(lock->owner != current);
-
- if (lock->intent_lock_recurse) {
- --lock->intent_lock_recurse;
- return;
- }
-
+ if (type == SIX_LOCK_intent)
lock->owner = NULL;
- }
if (type == SIX_LOCK_read &&
lock->readers) {
smp_mb(); /* unlock barrier */
this_cpu_dec(*lock->readers);
+ smp_mb(); /* between unlocking and checking for waiters */
state.v = READ_ONCE(lock->state.v);
} else {
EBUG_ON(!(lock->state.v & l[type].held_mask));
six_lock_wakeup(lock, state, l[type].unlock_wakeup);
}
+__always_inline __flatten
+static void __six_unlock_type(struct six_lock *lock, enum six_lock_type type)
+{
+ EBUG_ON(type == SIX_LOCK_write &&
+ !(lock->state.v & __SIX_LOCK_HELD_intent));
+ EBUG_ON((type == SIX_LOCK_write ||
+ type == SIX_LOCK_intent) &&
+ lock->owner != current);
+
+ if (type != SIX_LOCK_write)
+ six_release(&lock->dep_map);
+
+ if (type == SIX_LOCK_intent &&
+ lock->intent_lock_recurse) {
+ --lock->intent_lock_recurse;
+ return;
+ }
+
+ do_six_unlock_type(lock, type);
+}
+
#define __SIX_LOCK(type) \
bool six_trylock_##type(struct six_lock *lock) \
{ \
} \
EXPORT_SYMBOL_GPL(six_lock_##type); \
\
+int six_lock_waiter_##type(struct six_lock *lock, \
+ struct six_lock_waiter *wait, \
+ six_lock_should_sleep_fn should_sleep_fn, void *p)\
+{ \
+ return __six_lock_type_waiter(lock, SIX_LOCK_##type, wait, should_sleep_fn, p);\
+} \
+EXPORT_SYMBOL_GPL(six_lock_waiter_##type); \
+ \
void six_unlock_##type(struct six_lock *lock) \
{ \
__six_unlock_type(lock, SIX_LOCK_##type); \
if (lock->readers)
this_cpu_dec(*lock->readers);
- six_set_owner(lock, SIX_LOCK_intent, old);
+ six_set_owner(lock, SIX_LOCK_intent, old, current);
return true;
}
{
const struct six_lock_vals l[] = LOCK_VALS;
- six_acquire(&lock->dep_map, 0);
+ six_acquire(&lock->dep_map, 0, type == SIX_LOCK_read);
/* XXX: assert already locked, and that we don't overflow: */
void six_lock_wakeup_all(struct six_lock *lock)
{
+ union six_lock_state state = lock->state;
struct six_lock_waiter *w;
- raw_spin_lock(&lock->wait_lock);
+ six_lock_wakeup(lock, state, SIX_LOCK_read);
+ six_lock_wakeup(lock, state, SIX_LOCK_intent);
+ six_lock_wakeup(lock, state, SIX_LOCK_write);
- list_for_each_entry(w, &lock->wait_list[0], list)
- wake_up_process(w->task);
- list_for_each_entry(w, &lock->wait_list[1], list)
+ raw_spin_lock(&lock->wait_lock);
+ list_for_each_entry(w, &lock->wait_list, list)
wake_up_process(w->task);
-
raw_spin_unlock(&lock->wait_lock);
}
EXPORT_SYMBOL_GPL(six_lock_wakeup_all);
void six_lock_pcpu_alloc(struct six_lock *lock)
{
- BUG_ON(lock->readers && pcpu_read_count(lock));
- BUG_ON(lock->state.read_lock);
#ifdef __KERNEL__
if (!lock->readers)
lock->readers = alloc_percpu(unsigned);
#endif
}
EXPORT_SYMBOL_GPL(six_lock_pcpu_alloc);
+
+/*
+ * Returns lock held counts, for both read and intent
+ */
+struct six_lock_count six_lock_counts(struct six_lock *lock)
+{
+ struct six_lock_count ret;
+
+ ret.n[SIX_LOCK_read] = 0;
+ ret.n[SIX_LOCK_intent] = lock->state.intent_lock + lock->intent_lock_recurse;
+ ret.n[SIX_LOCK_write] = lock->state.seq & 1;
+
+ if (!lock->readers)
+ ret.n[SIX_LOCK_read] += lock->state.read_lock;
+ else {
+ int cpu;
+
+ for_each_possible_cpu(cpu)
+ ret.n[SIX_LOCK_read] += *per_cpu_ptr(lock->readers, cpu);
+ }
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(six_lock_counts);
projects / bcachefs-tools-debian / blobdiff