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linux/kernel/locking/spinlock_rt.c
Minchan Kim 4a57d6bbae locking/rwlocks: introduce write_lock_nested
In preparation for converting bit_spin_lock to rwlock in zsmalloc so
that multiple writers of zspages can run at the same time but those
zspages are supposed to be different zspage instance.  Thus, it's not
deadlock.  This patch adds write_lock_nested to support the case for
LOCKDEP.

[minchan@kernel.org: fix write_lock_nested for RT]
  Link: https://lkml.kernel.org/r/YZfrMTAXV56HFWJY@google.com
[bigeasy@linutronix.de: fixup write_lock_nested() implementation]
  Link: https://lkml.kernel.org/r/20211123170134.y6xb7pmpgdn4m3bn@linutronix.de

Link: https://lkml.kernel.org/r/20211115185909.3949505-8-minchan@kernel.org
Signed-off-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Tested-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Mike Galbraith <umgwanakikbuti@gmail.com>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Naresh Kamboju <naresh.kamboju@linaro.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2022-01-22 08:33:37 +02:00

281 lines
6.9 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* PREEMPT_RT substitution for spin/rw_locks
*
* spinlocks and rwlocks on RT are based on rtmutexes, with a few twists to
* resemble the non RT semantics:
*
* - Contrary to plain rtmutexes, spinlocks and rwlocks are state
* preserving. The task state is saved before blocking on the underlying
* rtmutex, and restored when the lock has been acquired. Regular wakeups
* during that time are redirected to the saved state so no wake up is
* missed.
*
* - Non RT spin/rwlocks disable preemption and eventually interrupts.
* Disabling preemption has the side effect of disabling migration and
* preventing RCU grace periods.
*
* The RT substitutions explicitly disable migration and take
* rcu_read_lock() across the lock held section.
*/
#include <linux/spinlock.h>
#include <linux/export.h>
#define RT_MUTEX_BUILD_SPINLOCKS
#include "rtmutex.c"
/*
* __might_resched() skips the state check as rtlocks are state
* preserving. Take RCU nesting into account as spin/read/write_lock() can
* legitimately nest into an RCU read side critical section.
*/
#define RTLOCK_RESCHED_OFFSETS \
(rcu_preempt_depth() << MIGHT_RESCHED_RCU_SHIFT)
#define rtlock_might_resched() \
__might_resched(__FILE__, __LINE__, RTLOCK_RESCHED_OFFSETS)
static __always_inline void rtlock_lock(struct rt_mutex_base *rtm)
{
if (unlikely(!rt_mutex_cmpxchg_acquire(rtm, NULL, current)))
rtlock_slowlock(rtm);
}
static __always_inline void __rt_spin_lock(spinlock_t *lock)
{
rtlock_might_resched();
rtlock_lock(&lock->lock);
rcu_read_lock();
migrate_disable();
}
void __sched rt_spin_lock(spinlock_t *lock)
{
spin_acquire(&lock->dep_map, 0, 0, _RET_IP_);
__rt_spin_lock(lock);
}
EXPORT_SYMBOL(rt_spin_lock);
#ifdef CONFIG_DEBUG_LOCK_ALLOC
void __sched rt_spin_lock_nested(spinlock_t *lock, int subclass)
{
spin_acquire(&lock->dep_map, subclass, 0, _RET_IP_);
__rt_spin_lock(lock);
}
EXPORT_SYMBOL(rt_spin_lock_nested);
void __sched rt_spin_lock_nest_lock(spinlock_t *lock,
struct lockdep_map *nest_lock)
{
spin_acquire_nest(&lock->dep_map, 0, 0, nest_lock, _RET_IP_);
__rt_spin_lock(lock);
}
EXPORT_SYMBOL(rt_spin_lock_nest_lock);
#endif
void __sched rt_spin_unlock(spinlock_t *lock)
{
spin_release(&lock->dep_map, _RET_IP_);
migrate_enable();
rcu_read_unlock();
if (unlikely(!rt_mutex_cmpxchg_release(&lock->lock, current, NULL)))
rt_mutex_slowunlock(&lock->lock);
}
EXPORT_SYMBOL(rt_spin_unlock);
/*
* Wait for the lock to get unlocked: instead of polling for an unlock
* (like raw spinlocks do), lock and unlock, to force the kernel to
* schedule if there's contention:
*/
void __sched rt_spin_lock_unlock(spinlock_t *lock)
{
spin_lock(lock);
spin_unlock(lock);
}
EXPORT_SYMBOL(rt_spin_lock_unlock);
static __always_inline int __rt_spin_trylock(spinlock_t *lock)
{
int ret = 1;
if (unlikely(!rt_mutex_cmpxchg_acquire(&lock->lock, NULL, current)))
ret = rt_mutex_slowtrylock(&lock->lock);
if (ret) {
spin_acquire(&lock->dep_map, 0, 1, _RET_IP_);
rcu_read_lock();
migrate_disable();
}
return ret;
}
int __sched rt_spin_trylock(spinlock_t *lock)
{
return __rt_spin_trylock(lock);
}
EXPORT_SYMBOL(rt_spin_trylock);
int __sched rt_spin_trylock_bh(spinlock_t *lock)
{
int ret;
local_bh_disable();
ret = __rt_spin_trylock(lock);
if (!ret)
local_bh_enable();
return ret;
}
EXPORT_SYMBOL(rt_spin_trylock_bh);
#ifdef CONFIG_DEBUG_LOCK_ALLOC
void __rt_spin_lock_init(spinlock_t *lock, const char *name,
struct lock_class_key *key, bool percpu)
{
u8 type = percpu ? LD_LOCK_PERCPU : LD_LOCK_NORMAL;
debug_check_no_locks_freed((void *)lock, sizeof(*lock));
lockdep_init_map_type(&lock->dep_map, name, key, 0, LD_WAIT_CONFIG,
LD_WAIT_INV, type);
}
EXPORT_SYMBOL(__rt_spin_lock_init);
#endif
/*
* RT-specific reader/writer locks
*/
#define rwbase_set_and_save_current_state(state) \
current_save_and_set_rtlock_wait_state()
#define rwbase_restore_current_state() \
current_restore_rtlock_saved_state()
static __always_inline int
rwbase_rtmutex_lock_state(struct rt_mutex_base *rtm, unsigned int state)
{
if (unlikely(!rt_mutex_cmpxchg_acquire(rtm, NULL, current)))
rtlock_slowlock(rtm);
return 0;
}
static __always_inline int
rwbase_rtmutex_slowlock_locked(struct rt_mutex_base *rtm, unsigned int state)
{
rtlock_slowlock_locked(rtm);
return 0;
}
static __always_inline void rwbase_rtmutex_unlock(struct rt_mutex_base *rtm)
{
if (likely(rt_mutex_cmpxchg_acquire(rtm, current, NULL)))
return;
rt_mutex_slowunlock(rtm);
}
static __always_inline int rwbase_rtmutex_trylock(struct rt_mutex_base *rtm)
{
if (likely(rt_mutex_cmpxchg_acquire(rtm, NULL, current)))
return 1;
return rt_mutex_slowtrylock(rtm);
}
#define rwbase_signal_pending_state(state, current) (0)
#define rwbase_schedule() \
schedule_rtlock()
#include "rwbase_rt.c"
/*
* The common functions which get wrapped into the rwlock API.
*/
int __sched rt_read_trylock(rwlock_t *rwlock)
{
int ret;
ret = rwbase_read_trylock(&rwlock->rwbase);
if (ret) {
rwlock_acquire_read(&rwlock->dep_map, 0, 1, _RET_IP_);
rcu_read_lock();
migrate_disable();
}
return ret;
}
EXPORT_SYMBOL(rt_read_trylock);
int __sched rt_write_trylock(rwlock_t *rwlock)
{
int ret;
ret = rwbase_write_trylock(&rwlock->rwbase);
if (ret) {
rwlock_acquire(&rwlock->dep_map, 0, 1, _RET_IP_);
rcu_read_lock();
migrate_disable();
}
return ret;
}
EXPORT_SYMBOL(rt_write_trylock);
void __sched rt_read_lock(rwlock_t *rwlock)
{
rtlock_might_resched();
rwlock_acquire_read(&rwlock->dep_map, 0, 0, _RET_IP_);
rwbase_read_lock(&rwlock->rwbase, TASK_RTLOCK_WAIT);
rcu_read_lock();
migrate_disable();
}
EXPORT_SYMBOL(rt_read_lock);
void __sched rt_write_lock(rwlock_t *rwlock)
{
rtlock_might_resched();
rwlock_acquire(&rwlock->dep_map, 0, 0, _RET_IP_);
rwbase_write_lock(&rwlock->rwbase, TASK_RTLOCK_WAIT);
rcu_read_lock();
migrate_disable();
}
EXPORT_SYMBOL(rt_write_lock);
#ifdef CONFIG_DEBUG_LOCK_ALLOC
void __sched rt_write_lock_nested(rwlock_t *rwlock, int subclass)
{
rtlock_might_resched();
rwlock_acquire(&rwlock->dep_map, subclass, 0, _RET_IP_);
rwbase_write_lock(&rwlock->rwbase, TASK_RTLOCK_WAIT);
rcu_read_lock();
migrate_disable();
}
EXPORT_SYMBOL(rt_write_lock_nested);
#endif
void __sched rt_read_unlock(rwlock_t *rwlock)
{
rwlock_release(&rwlock->dep_map, _RET_IP_);
migrate_enable();
rcu_read_unlock();
rwbase_read_unlock(&rwlock->rwbase, TASK_RTLOCK_WAIT);
}
EXPORT_SYMBOL(rt_read_unlock);
void __sched rt_write_unlock(rwlock_t *rwlock)
{
rwlock_release(&rwlock->dep_map, _RET_IP_);
rcu_read_unlock();
migrate_enable();
rwbase_write_unlock(&rwlock->rwbase);
}
EXPORT_SYMBOL(rt_write_unlock);
#ifdef CONFIG_DEBUG_LOCK_ALLOC
void __rt_rwlock_init(rwlock_t *rwlock, const char *name,
struct lock_class_key *key)
{
debug_check_no_locks_freed((void *)rwlock, sizeof(*rwlock));
lockdep_init_map_wait(&rwlock->dep_map, name, key, 0, LD_WAIT_CONFIG);
}
EXPORT_SYMBOL(__rt_rwlock_init);
#endif