cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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percpu-rwsem.h (4257B)

      1/* SPDX-License-Identifier: GPL-2.0 */
      2#ifndef _LINUX_PERCPU_RWSEM_H
      3#define _LINUX_PERCPU_RWSEM_H
      4
      5#include <linux/atomic.h>
      6#include <linux/percpu.h>
      7#include <linux/rcuwait.h>
      8#include <linux/wait.h>
      9#include <linux/rcu_sync.h>
     10#include <linux/lockdep.h>
     11
     12struct percpu_rw_semaphore {
     13	struct rcu_sync		rss;
     14	unsigned int __percpu	*read_count;
     15	struct rcuwait		writer;
     16	wait_queue_head_t	waiters;
     17	atomic_t		block;
     18#ifdef CONFIG_DEBUG_LOCK_ALLOC
     19	struct lockdep_map	dep_map;
     20#endif
     21};
     22
     23#ifdef CONFIG_DEBUG_LOCK_ALLOC
     24#define __PERCPU_RWSEM_DEP_MAP_INIT(lockname)	.dep_map = { .name = #lockname },
     25#else
     26#define __PERCPU_RWSEM_DEP_MAP_INIT(lockname)
     27#endif
     28
     29#define __DEFINE_PERCPU_RWSEM(name, is_static)				\
     30static DEFINE_PER_CPU(unsigned int, __percpu_rwsem_rc_##name);		\
     31is_static struct percpu_rw_semaphore name = {				\
     32	.rss = __RCU_SYNC_INITIALIZER(name.rss),			\
     33	.read_count = &__percpu_rwsem_rc_##name,			\
     34	.writer = __RCUWAIT_INITIALIZER(name.writer),			\
     35	.waiters = __WAIT_QUEUE_HEAD_INITIALIZER(name.waiters),		\
     36	.block = ATOMIC_INIT(0),					\
     37	__PERCPU_RWSEM_DEP_MAP_INIT(name)				\
     38}
     39
     40#define DEFINE_PERCPU_RWSEM(name)		\
     41	__DEFINE_PERCPU_RWSEM(name, /* not static */)
     42#define DEFINE_STATIC_PERCPU_RWSEM(name)	\
     43	__DEFINE_PERCPU_RWSEM(name, static)
     44
     45extern bool __percpu_down_read(struct percpu_rw_semaphore *, bool);
     46
     47static inline void percpu_down_read(struct percpu_rw_semaphore *sem)
     48{
     49	might_sleep();
     50
     51	rwsem_acquire_read(&sem->dep_map, 0, 0, _RET_IP_);
     52
     53	preempt_disable();
     54	/*
     55	 * We are in an RCU-sched read-side critical section, so the writer
     56	 * cannot both change sem->state from readers_fast and start checking
     57	 * counters while we are here. So if we see !sem->state, we know that
     58	 * the writer won't be checking until we're past the preempt_enable()
     59	 * and that once the synchronize_rcu() is done, the writer will see
     60	 * anything we did within this RCU-sched read-size critical section.
     61	 */
     62	if (likely(rcu_sync_is_idle(&sem->rss)))
     63		this_cpu_inc(*sem->read_count);
     64	else
     65		__percpu_down_read(sem, false); /* Unconditional memory barrier */
     66	/*
     67	 * The preempt_enable() prevents the compiler from
     68	 * bleeding the critical section out.
     69	 */
     70	preempt_enable();
     71}
     72
     73static inline bool percpu_down_read_trylock(struct percpu_rw_semaphore *sem)
     74{
     75	bool ret = true;
     76
     77	preempt_disable();
     78	/*
     79	 * Same as in percpu_down_read().
     80	 */
     81	if (likely(rcu_sync_is_idle(&sem->rss)))
     82		this_cpu_inc(*sem->read_count);
     83	else
     84		ret = __percpu_down_read(sem, true); /* Unconditional memory barrier */
     85	preempt_enable();
     86	/*
     87	 * The barrier() from preempt_enable() prevents the compiler from
     88	 * bleeding the critical section out.
     89	 */
     90
     91	if (ret)
     92		rwsem_acquire_read(&sem->dep_map, 0, 1, _RET_IP_);
     93
     94	return ret;
     95}
     96
     97static inline void percpu_up_read(struct percpu_rw_semaphore *sem)
     98{
     99	rwsem_release(&sem->dep_map, _RET_IP_);
    100
    101	preempt_disable();
    102	/*
    103	 * Same as in percpu_down_read().
    104	 */
    105	if (likely(rcu_sync_is_idle(&sem->rss))) {
    106		this_cpu_dec(*sem->read_count);
    107	} else {
    108		/*
    109		 * slowpath; reader will only ever wake a single blocked
    110		 * writer.
    111		 */
    112		smp_mb(); /* B matches C */
    113		/*
    114		 * In other words, if they see our decrement (presumably to
    115		 * aggregate zero, as that is the only time it matters) they
    116		 * will also see our critical section.
    117		 */
    118		this_cpu_dec(*sem->read_count);
    119		rcuwait_wake_up(&sem->writer);
    120	}
    121	preempt_enable();
    122}
    123
    124extern void percpu_down_write(struct percpu_rw_semaphore *);
    125extern void percpu_up_write(struct percpu_rw_semaphore *);
    126
    127extern int __percpu_init_rwsem(struct percpu_rw_semaphore *,
    128				const char *, struct lock_class_key *);
    129
    130extern void percpu_free_rwsem(struct percpu_rw_semaphore *);
    131
    132#define percpu_init_rwsem(sem)					\
    133({								\
    134	static struct lock_class_key rwsem_key;			\
    135	__percpu_init_rwsem(sem, #sem, &rwsem_key);		\
    136})
    137
    138#define percpu_rwsem_is_held(sem)	lockdep_is_held(sem)
    139#define percpu_rwsem_assert_held(sem)	lockdep_assert_held(sem)
    140
    141static inline void percpu_rwsem_release(struct percpu_rw_semaphore *sem,
    142					bool read, unsigned long ip)
    143{
    144	lock_release(&sem->dep_map, ip);
    145}
    146
    147static inline void percpu_rwsem_acquire(struct percpu_rw_semaphore *sem,
    148					bool read, unsigned long ip)
    149{
    150	lock_acquire(&sem->dep_map, 0, 1, read, 1, NULL, ip);
    151}
    152
    153#endif