+++ /dev/null
-// SPDX-License-Identifier: GPL-2.0
-
-#include <linux/export.h>
-#include <linux/log2.h>
-#include <linux/percpu.h>
-#include <linux/preempt.h>
-#include <linux/rcupdate.h>
-#include <linux/sched.h>
-#include <linux/sched/clock.h>
-#include <linux/sched/rt.h>
-#include <linux/sched/task.h>
-#include <linux/slab.h>
-
-#include <trace/events/lock.h>
-
-#include "six.h"
-
-#ifdef DEBUG
-#define EBUG_ON(cond) BUG_ON(cond)
-#else
-#define EBUG_ON(cond) do {} while (0)
-#endif
-
-#define six_acquire(l, t, r, ip) lock_acquire(l, 0, t, r, 1, NULL, ip)
-#define six_release(l, ip) lock_release(l, ip)
-
-static void do_six_unlock_type(struct six_lock *lock, enum six_lock_type type);
-
-#define SIX_LOCK_HELD_read_OFFSET 0
-#define SIX_LOCK_HELD_read ~(~0U << 26)
-#define SIX_LOCK_HELD_intent (1U << 26)
-#define SIX_LOCK_HELD_write (1U << 27)
-#define SIX_LOCK_WAITING_read (1U << (28 + SIX_LOCK_read))
-#define SIX_LOCK_WAITING_write (1U << (28 + SIX_LOCK_write))
-#define SIX_LOCK_NOSPIN (1U << 31)
-
-struct six_lock_vals {
- /* Value we add to the lock in order to take the lock: */
- u32 lock_val;
-
- /* If the lock has this value (used as a mask), taking the lock fails: */
- u32 lock_fail;
-
- /* Mask that indicates lock is held for this type: */
- u32 held_mask;
-
- /* Waitlist we wakeup when releasing the lock: */
- enum six_lock_type unlock_wakeup;
-};
-
-static const struct six_lock_vals l[] = {
- [SIX_LOCK_read] = {
- .lock_val = 1U << SIX_LOCK_HELD_read_OFFSET,
- .lock_fail = SIX_LOCK_HELD_write,
- .held_mask = SIX_LOCK_HELD_read,
- .unlock_wakeup = SIX_LOCK_write,
- },
- [SIX_LOCK_intent] = {
- .lock_val = SIX_LOCK_HELD_intent,
- .lock_fail = SIX_LOCK_HELD_intent,
- .held_mask = SIX_LOCK_HELD_intent,
- .unlock_wakeup = SIX_LOCK_intent,
- },
- [SIX_LOCK_write] = {
- .lock_val = SIX_LOCK_HELD_write,
- .lock_fail = SIX_LOCK_HELD_read,
- .held_mask = SIX_LOCK_HELD_write,
- .unlock_wakeup = SIX_LOCK_read,
- },
-};
-
-static inline void six_set_bitmask(struct six_lock *lock, u32 mask)
-{
- if ((atomic_read(&lock->state) & mask) != mask)
- atomic_or(mask, &lock->state);
-}
-
-static inline void six_clear_bitmask(struct six_lock *lock, u32 mask)
-{
- if (atomic_read(&lock->state) & mask)
- atomic_and(~mask, &lock->state);
-}
-
-static inline void six_set_owner(struct six_lock *lock, enum six_lock_type type,
- u32 old, struct task_struct *owner)
-{
- if (type != SIX_LOCK_intent)
- return;
-
- if (!(old & SIX_LOCK_HELD_intent)) {
- EBUG_ON(lock->owner);
- lock->owner = owner;
- } else {
- EBUG_ON(lock->owner != current);
- }
-}
-
-static inline unsigned pcpu_read_count(struct six_lock *lock)
-{
- unsigned read_count = 0;
- int cpu;
-
- for_each_possible_cpu(cpu)
- read_count += *per_cpu_ptr(lock->readers, cpu);
- return read_count;
-}
-
-/*
- * __do_six_trylock() - main trylock routine
- *
- * Returns 1 on success, 0 on failure
- *
- * In percpu reader mode, a failed trylock may cause a spurious trylock failure
- * for anoter thread taking the competing lock type, and we may havve to do a
- * wakeup: when a wakeup is required, we return -1 - wakeup_type.
- */
-static int __do_six_trylock(struct six_lock *lock, enum six_lock_type type,
- struct task_struct *task, bool try)
-{
- int ret;
- u32 old;
-
- EBUG_ON(type == SIX_LOCK_write && lock->owner != task);
- EBUG_ON(type == SIX_LOCK_write &&
- (try != !(atomic_read(&lock->state) & SIX_LOCK_HELD_write)));
-
- /*
- * Percpu reader mode:
- *
- * The basic idea behind this algorithm is that you can implement a lock
- * between two threads without any atomics, just memory barriers:
- *
- * For two threads you'll need two variables, one variable for "thread a
- * has the lock" and another for "thread b has the lock".
- *
- * To take the lock, a thread sets its variable indicating that it holds
- * the lock, then issues a full memory barrier, then reads from the
- * other thread's variable to check if the other thread thinks it has
- * the lock. If we raced, we backoff and retry/sleep.
- *
- * Failure to take the lock may cause a spurious trylock failure in
- * another thread, because we temporarily set the lock to indicate that
- * we held it. This would be a problem for a thread in six_lock(), when
- * they are calling trylock after adding themself to the waitlist and
- * prior to sleeping.
- *
- * Therefore, if we fail to get the lock, and there were waiters of the
- * type we conflict with, we will have to issue a wakeup.
- *
- * Since we may be called under wait_lock (and by the wakeup code
- * itself), we return that the wakeup has to be done instead of doing it
- * here.
- */
- if (type == SIX_LOCK_read && lock->readers) {
- preempt_disable();
- this_cpu_inc(*lock->readers); /* signal that we own lock */
-
- smp_mb();
-
- old = atomic_read(&lock->state);
- ret = !(old & l[type].lock_fail);
-
- this_cpu_sub(*lock->readers, !ret);
- preempt_enable();
-
- if (!ret) {
- smp_mb();
- if (atomic_read(&lock->state) & SIX_LOCK_WAITING_write)
- ret = -1 - SIX_LOCK_write;
- }
- } else if (type == SIX_LOCK_write && lock->readers) {
- if (try) {
- atomic_add(SIX_LOCK_HELD_write, &lock->state);
- smp_mb__after_atomic();
- }
-
- ret = !pcpu_read_count(lock);
-
- if (try && !ret) {
- old = atomic_sub_return(SIX_LOCK_HELD_write, &lock->state);
- if (old & SIX_LOCK_WAITING_read)
- ret = -1 - SIX_LOCK_read;
- }
- } else {
- old = atomic_read(&lock->state);
- do {
- ret = !(old & l[type].lock_fail);
- if (!ret || (type == SIX_LOCK_write && !try)) {
- smp_mb();
- break;
- }
- } while (!atomic_try_cmpxchg_acquire(&lock->state, &old, old + l[type].lock_val));
-
- EBUG_ON(ret && !(atomic_read(&lock->state) & l[type].held_mask));
- }
-
- if (ret > 0)
- six_set_owner(lock, type, old, task);
-
- EBUG_ON(type == SIX_LOCK_write && try && ret <= 0 &&
- (atomic_read(&lock->state) & SIX_LOCK_HELD_write));
-
- return ret;
-}
-
-static 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(lock, lock_type, w->task, false);
- if (ret <= 0)
- goto unlock;
-
- /*
- * Similar to percpu_rwsem_wake_function(), we need to guard
- * against the wakee noticing w->lock_acquired, returning, and
- * then exiting before we do the wakeup:
- */
- task = get_task_struct(w->task);
- __list_del(w->list.prev, w->list.next);
- /*
- * The release barrier here ensures the ordering of the
- * __list_del before setting w->lock_acquired; @w is on the
- * stack of the thread doing the waiting and will be reused
- * after it sees w->lock_acquired with no other locking:
- * pairs with smp_load_acquire() in six_lock_slowpath()
- */
- smp_store_release(&w->lock_acquired, true);
- wake_up_process(task);
- put_task_struct(task);
- }
-
- six_clear_bitmask(lock, SIX_LOCK_WAITING_read << lock_type);
-unlock:
- raw_spin_unlock(&lock->wait_lock);
-
- if (ret < 0) {
- lock_type = -ret - 1;
- goto again;
- }
-}
-
-__always_inline
-static void six_lock_wakeup(struct six_lock *lock, u32 state,
- enum six_lock_type lock_type)
-{
- if (lock_type == SIX_LOCK_write && (state & SIX_LOCK_HELD_read))
- return;
-
- if (!(state & (SIX_LOCK_WAITING_read << lock_type)))
- return;
-
- __six_lock_wakeup(lock, lock_type);
-}
-
-__always_inline
-static bool do_six_trylock(struct six_lock *lock, enum six_lock_type type, bool try)
-{
- int ret;
-
- ret = __do_six_trylock(lock, type, current, try);
- if (ret < 0)
- __six_lock_wakeup(lock, -ret - 1);
-
- return ret > 0;
-}
-
-/**
- * six_trylock_ip - attempt to take a six lock without blocking
- * @lock: lock to take
- * @type: SIX_LOCK_read, SIX_LOCK_intent, or SIX_LOCK_write
- * @ip: ip parameter for lockdep/lockstat, i.e. _THIS_IP_
- *
- * Return: true on success, false on failure.
- */
-bool six_trylock_ip(struct six_lock *lock, enum six_lock_type type, unsigned long ip)
-{
- if (!do_six_trylock(lock, type, true))
- return false;
-
- if (type != SIX_LOCK_write)
- six_acquire(&lock->dep_map, 1, type == SIX_LOCK_read, ip);
- return true;
-}
-EXPORT_SYMBOL_GPL(six_trylock_ip);
-
-/**
- * six_relock_ip - attempt to re-take a lock that was held previously
- * @lock: lock to take
- * @type: SIX_LOCK_read, SIX_LOCK_intent, or SIX_LOCK_write
- * @seq: lock sequence number obtained from six_lock_seq() while lock was
- * held previously
- * @ip: ip parameter for lockdep/lockstat, i.e. _THIS_IP_
- *
- * Return: true on success, false on failure.
- */
-bool six_relock_ip(struct six_lock *lock, enum six_lock_type type,
- unsigned seq, unsigned long ip)
-{
- if (six_lock_seq(lock) != seq || !six_trylock_ip(lock, type, ip))
- return false;
-
- if (six_lock_seq(lock) != seq) {
- six_unlock_ip(lock, type, ip);
- return false;
- }
-
- return true;
-}
-EXPORT_SYMBOL_GPL(six_relock_ip);
-
-#ifdef CONFIG_BCACHEFS_SIX_OPTIMISTIC_SPIN
-
-static inline bool six_owner_running(struct six_lock *lock)
-{
- /*
- * 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 the owner complete.
- */
- rcu_read_lock();
- struct task_struct *owner = READ_ONCE(lock->owner);
- bool ret = owner ? owner_on_cpu(owner) : !rt_task(current);
- rcu_read_unlock();
-
- return ret;
-}
-
-static inline bool six_optimistic_spin(struct six_lock *lock,
- struct six_lock_waiter *wait,
- enum six_lock_type type)
-{
- unsigned loop = 0;
- u64 end_time;
-
- if (type == SIX_LOCK_write)
- return false;
-
- if (lock->wait_list.next != &wait->list)
- return false;
-
- if (atomic_read(&lock->state) & SIX_LOCK_NOSPIN)
- return false;
-
- preempt_disable();
- end_time = sched_clock() + 10 * NSEC_PER_USEC;
-
- while (!need_resched() && six_owner_running(lock)) {
- /*
- * Ensures that writes to the waitlist entry happen after we see
- * wait->lock_acquired: pairs with the smp_store_release in
- * __six_lock_wakeup
- */
- if (smp_load_acquire(&wait->lock_acquired)) {
- preempt_enable();
- return true;
- }
-
- if (!(++loop & 0xf) && (time_after64(sched_clock(), end_time))) {
- six_set_bitmask(lock, SIX_LOCK_NOSPIN);
- 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();
- }
-
- preempt_enable();
- return false;
-}
-
-#else /* CONFIG_LOCK_SPIN_ON_OWNER */
-
-static inline bool six_optimistic_spin(struct six_lock *lock,
- struct six_lock_waiter *wait,
- enum six_lock_type type)
-{
- return false;
-}
-
-#endif
-
-noinline
-static int six_lock_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,
- unsigned long ip)
-{
- int ret = 0;
-
- if (type == SIX_LOCK_write) {
- EBUG_ON(atomic_read(&lock->state) & SIX_LOCK_HELD_write);
- atomic_add(SIX_LOCK_HELD_write, &lock->state);
- smp_mb__after_atomic();
- }
-
- trace_contention_begin(lock, 0);
- lock_contended(&lock->dep_map, ip);
-
- wait->task = current;
- wait->lock_want = type;
- wait->lock_acquired = false;
-
- raw_spin_lock(&lock->wait_lock);
- six_set_bitmask(lock, SIX_LOCK_WAITING_read << type);
- /*
- * Retry taking the lock after taking waitlist lock, in case we raced
- * with an unlock:
- */
- ret = __do_six_trylock(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;
- }
-
- if (unlikely(ret < 0)) {
- __six_lock_wakeup(lock, -ret - 1);
- ret = 0;
- }
-
- if (six_optimistic_spin(lock, wait, type))
- goto out;
-
- while (1) {
- set_current_state(TASK_UNINTERRUPTIBLE);
-
- /*
- * Ensures that writes to the waitlist entry happen after we see
- * wait->lock_acquired: pairs with the smp_store_release in
- * __six_lock_wakeup
- */
- if (smp_load_acquire(&wait->lock_acquired))
- break;
-
- ret = should_sleep_fn ? should_sleep_fn(lock, p) : 0;
- if (unlikely(ret)) {
- bool acquired;
-
- /*
- * If should_sleep_fn() returns an error, we are
- * required to return that error even if we already
- * acquired the lock - should_sleep_fn() might have
- * modified external state (e.g. when the deadlock cycle
- * detector in bcachefs issued a transaction restart)
- */
- raw_spin_lock(&lock->wait_lock);
- acquired = wait->lock_acquired;
- if (!acquired)
- list_del(&wait->list);
- raw_spin_unlock(&lock->wait_lock);
-
- if (unlikely(acquired))
- do_six_unlock_type(lock, type);
- break;
- }
-
- schedule();
- }
-
- __set_current_state(TASK_RUNNING);
-out:
- if (ret && type == SIX_LOCK_write) {
- six_clear_bitmask(lock, SIX_LOCK_HELD_write);
- six_lock_wakeup(lock, atomic_read(&lock->state), SIX_LOCK_read);
- }
- trace_contention_end(lock, 0);
-
- return ret;
-}
-
-/**
- * six_lock_ip_waiter - take a lock, with full waitlist interface
- * @lock: lock to take
- * @type: SIX_LOCK_read, SIX_LOCK_intent, or SIX_LOCK_write
- * @wait: pointer to wait object, which will be added to lock's waitlist
- * @should_sleep_fn: callback run after adding to waitlist, immediately prior
- * to scheduling
- * @p: passed through to @should_sleep_fn
- * @ip: ip parameter for lockdep/lockstat, i.e. _THIS_IP_
- *
- * This is the most general six_lock() variant, with parameters to support full
- * cycle detection for deadlock avoidance.
- *
- * The code calling this function must implement tracking of held locks, and the
- * @wait object should be embedded into the struct that tracks held locks -
- * which must also be accessible in a thread-safe way.
- *
- * @should_sleep_fn should invoke the cycle detector; it should walk each
- * lock's waiters, and for each waiter recursively walk their held locks.
- *
- * When this function must block, @wait will be added to @lock's waitlist before
- * calling trylock, and before calling @should_sleep_fn, and @wait will not be
- * removed from the lock waitlist until the lock has been successfully acquired,
- * or we abort.
- *
- * @wait.start_time will be monotonically increasing for any given waitlist, and
- * thus may be used as a loop cursor.
- *
- * Return: 0 on success, or the return code from @should_sleep_fn on failure.
- */
-int six_lock_ip_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,
- unsigned long ip)
-{
- int ret;
-
- wait->start_time = 0;
-
- if (type != SIX_LOCK_write)
- six_acquire(&lock->dep_map, 0, type == SIX_LOCK_read, ip);
-
- ret = do_six_trylock(lock, type, true) ? 0
- : six_lock_slowpath(lock, type, wait, should_sleep_fn, p, ip);
-
- if (ret && type != SIX_LOCK_write)
- six_release(&lock->dep_map, ip);
- if (!ret)
- lock_acquired(&lock->dep_map, ip);
-
- return ret;
-}
-EXPORT_SYMBOL_GPL(six_lock_ip_waiter);
-
-__always_inline
-static void do_six_unlock_type(struct six_lock *lock, enum six_lock_type type)
-{
- u32 state;
-
- 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 = atomic_read(&lock->state);
- } else {
- u32 v = l[type].lock_val;
-
- if (type != SIX_LOCK_read)
- v += atomic_read(&lock->state) & SIX_LOCK_NOSPIN;
-
- EBUG_ON(!(atomic_read(&lock->state) & l[type].held_mask));
- state = atomic_sub_return_release(v, &lock->state);
- }
-
- six_lock_wakeup(lock, state, l[type].unlock_wakeup);
-}
-
-/**
- * six_unlock_ip - drop a six lock
- * @lock: lock to unlock
- * @type: SIX_LOCK_read, SIX_LOCK_intent, or SIX_LOCK_write
- * @ip: ip parameter for lockdep/lockstat, i.e. _THIS_IP_
- *
- * When a lock is held multiple times (because six_lock_incement()) was used),
- * this decrements the 'lock held' counter by one.
- *
- * For example:
- * six_lock_read(&foo->lock); read count 1
- * six_lock_increment(&foo->lock, SIX_LOCK_read); read count 2
- * six_lock_unlock(&foo->lock, SIX_LOCK_read); read count 1
- * six_lock_unlock(&foo->lock, SIX_LOCK_read); read count 0
- */
-void six_unlock_ip(struct six_lock *lock, enum six_lock_type type, unsigned long ip)
-{
- EBUG_ON(type == SIX_LOCK_write &&
- !(atomic_read(&lock->state) & 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, ip);
- else
- lock->seq++;
-
- if (type == SIX_LOCK_intent &&
- lock->intent_lock_recurse) {
- --lock->intent_lock_recurse;
- return;
- }
-
- do_six_unlock_type(lock, type);
-}
-EXPORT_SYMBOL_GPL(six_unlock_ip);
-
-/**
- * six_lock_downgrade - convert an intent lock to a read lock
- * @lock: lock to dowgrade
- *
- * @lock will have read count incremented and intent count decremented
- */
-void six_lock_downgrade(struct six_lock *lock)
-{
- six_lock_increment(lock, SIX_LOCK_read);
- six_unlock_intent(lock);
-}
-EXPORT_SYMBOL_GPL(six_lock_downgrade);
-
-/**
- * six_lock_tryupgrade - attempt to convert read lock to an intent lock
- * @lock: lock to upgrade
- *
- * On success, @lock will have intent count incremented and read count
- * decremented
- *
- * Return: true on success, false on failure
- */
-bool six_lock_tryupgrade(struct six_lock *lock)
-{
- u32 old = atomic_read(&lock->state), new;
-
- do {
- new = old;
-
- if (new & SIX_LOCK_HELD_intent)
- return false;
-
- if (!lock->readers) {
- EBUG_ON(!(new & SIX_LOCK_HELD_read));
- new -= l[SIX_LOCK_read].lock_val;
- }
-
- new |= SIX_LOCK_HELD_intent;
- } while (!atomic_try_cmpxchg_acquire(&lock->state, &old, new));
-
- if (lock->readers)
- this_cpu_dec(*lock->readers);
-
- six_set_owner(lock, SIX_LOCK_intent, old, current);
-
- return true;
-}
-EXPORT_SYMBOL_GPL(six_lock_tryupgrade);
-
-/**
- * six_trylock_convert - attempt to convert a held lock from one type to another
- * @lock: lock to upgrade
- * @from: SIX_LOCK_read or SIX_LOCK_intent
- * @to: SIX_LOCK_read or SIX_LOCK_intent
- *
- * On success, @lock will have intent count incremented and read count
- * decremented
- *
- * Return: true on success, false on failure
- */
-bool six_trylock_convert(struct six_lock *lock,
- enum six_lock_type from,
- enum six_lock_type to)
-{
- EBUG_ON(to == SIX_LOCK_write || from == SIX_LOCK_write);
-
- if (to == from)
- return true;
-
- if (to == SIX_LOCK_read) {
- six_lock_downgrade(lock);
- return true;
- } else {
- return six_lock_tryupgrade(lock);
- }
-}
-EXPORT_SYMBOL_GPL(six_trylock_convert);
-
-/**
- * six_lock_increment - increase held lock count on a lock that is already held
- * @lock: lock to increment
- * @type: SIX_LOCK_read or SIX_LOCK_intent
- *
- * @lock must already be held, with a lock type that is greater than or equal to
- * @type
- *
- * A corresponding six_unlock_type() call will be required for @lock to be fully
- * unlocked.
- */
-void six_lock_increment(struct six_lock *lock, enum six_lock_type type)
-{
- six_acquire(&lock->dep_map, 0, type == SIX_LOCK_read, _RET_IP_);
-
- /* XXX: assert already locked, and that we don't overflow: */
-
- switch (type) {
- case SIX_LOCK_read:
- if (lock->readers) {
- this_cpu_inc(*lock->readers);
- } else {
- EBUG_ON(!(atomic_read(&lock->state) &
- (SIX_LOCK_HELD_read|
- SIX_LOCK_HELD_intent)));
- atomic_add(l[type].lock_val, &lock->state);
- }
- break;
- case SIX_LOCK_intent:
- EBUG_ON(!(atomic_read(&lock->state) & SIX_LOCK_HELD_intent));
- lock->intent_lock_recurse++;
- break;
- case SIX_LOCK_write:
- BUG();
- break;
- }
-}
-EXPORT_SYMBOL_GPL(six_lock_increment);
-
-/**
- * six_lock_wakeup_all - wake up all waiters on @lock
- * @lock: lock to wake up waiters for
- *
- * Wakeing up waiters will cause them to re-run should_sleep_fn, which may then
- * abort the lock operation.
- *
- * This function is never needed in a bug-free program; it's only useful in
- * debug code, e.g. to determine if a cycle detector is at fault.
- */
-void six_lock_wakeup_all(struct six_lock *lock)
-{
- u32 state = atomic_read(&lock->state);
- struct six_lock_waiter *w;
-
- six_lock_wakeup(lock, state, SIX_LOCK_read);
- six_lock_wakeup(lock, state, SIX_LOCK_intent);
- six_lock_wakeup(lock, state, SIX_LOCK_write);
-
- 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);
-
-/**
- * six_lock_counts - return held lock counts, for each lock type
- * @lock: lock to return counters for
- *
- * Return: the number of times a lock is held for read, intent and write.
- */
-struct six_lock_count six_lock_counts(struct six_lock *lock)
-{
- struct six_lock_count ret;
-
- ret.n[SIX_LOCK_read] = !lock->readers
- ? atomic_read(&lock->state) & SIX_LOCK_HELD_read
- : pcpu_read_count(lock);
- ret.n[SIX_LOCK_intent] = !!(atomic_read(&lock->state) & SIX_LOCK_HELD_intent) +
- lock->intent_lock_recurse;
- ret.n[SIX_LOCK_write] = !!(atomic_read(&lock->state) & SIX_LOCK_HELD_write);
-
- return ret;
-}
-EXPORT_SYMBOL_GPL(six_lock_counts);
-
-/**
- * six_lock_readers_add - directly manipulate reader count of a lock
- * @lock: lock to add/subtract readers for
- * @nr: reader count to add/subtract
- *
- * When an upper layer is implementing lock reentrency, we may have both read
- * and intent locks on the same lock.
- *
- * When we need to take a write lock, the read locks will cause self-deadlock,
- * because six locks themselves do not track which read locks are held by the
- * current thread and which are held by a different thread - it does no
- * per-thread tracking of held locks.
- *
- * The upper layer that is tracking held locks may however, if trylock() has
- * failed, count up its own read locks, subtract them, take the write lock, and
- * then re-add them.
- *
- * As in any other situation when taking a write lock, @lock must be held for
- * intent one (or more) times, so @lock will never be left unlocked.
- */
-void six_lock_readers_add(struct six_lock *lock, int nr)
-{
- if (lock->readers) {
- this_cpu_add(*lock->readers, nr);
- } else {
- EBUG_ON((int) (atomic_read(&lock->state) & SIX_LOCK_HELD_read) + nr < 0);
- /* reader count starts at bit 0 */
- atomic_add(nr, &lock->state);
- }
-}
-EXPORT_SYMBOL_GPL(six_lock_readers_add);
-
-/**
- * six_lock_exit - release resources held by a lock prior to freeing
- * @lock: lock to exit
- *
- * When a lock was initialized in percpu mode (SIX_OLCK_INIT_PCPU), this is
- * required to free the percpu read counts.
- */
-void six_lock_exit(struct six_lock *lock)
-{
- WARN_ON(lock->readers && pcpu_read_count(lock));
- WARN_ON(atomic_read(&lock->state) & SIX_LOCK_HELD_read);
-
- free_percpu(lock->readers);
- lock->readers = NULL;
-}
-EXPORT_SYMBOL_GPL(six_lock_exit);
-
-void __six_lock_init(struct six_lock *lock, const char *name,
- struct lock_class_key *key, enum six_lock_init_flags flags)
-{
- atomic_set(&lock->state, 0);
- raw_spin_lock_init(&lock->wait_lock);
- INIT_LIST_HEAD(&lock->wait_list);
-#ifdef CONFIG_DEBUG_LOCK_ALLOC
- debug_check_no_locks_freed((void *) lock, sizeof(*lock));
- lockdep_init_map(&lock->dep_map, name, key, 0);
-#endif
-
- /*
- * Don't assume that we have real percpu variables available in
- * userspace:
- */
-#ifdef __KERNEL__
- if (flags & SIX_LOCK_INIT_PCPU) {
- /*
- * We don't return an error here on memory allocation failure
- * since percpu is an optimization, and locks will work with the
- * same semantics in non-percpu mode: callers can check for
- * failure if they wish by checking lock->readers, but generally
- * will not want to treat it as an error.
- */
- lock->readers = alloc_percpu(unsigned);
- }
-#endif
-}
-EXPORT_SYMBOL_GPL(__six_lock_init);
projects / bcachefs-tools-debian / blobdiff