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rcu/sync: Kill rcu_sync_type/gp_type

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Now that the RCU flavors have been consolidated, rcu_sync_type makes no
sense because none of internal update functions aside from .held() depend
on gp_type.  This commit therefore removes this field and consolidates
the relevant code.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
[ paulmck: Added RCU and RCU-bh checks to rcu_sync_is_idle(). ]
[ paulmck: And applied subsequent feedback from Oleg Nesterov. ]
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
This commit is contained in:
Oleg Nesterov 2019-04-23 14:07:24 +02:00 committed by Paul E. McKenney
parent a188339ca5
commit 95bf33b55f
4 changed files with 17 additions and 78 deletions
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2
include/linux/percpu-rwsem.h
View File

@ -20,7 +20,7 @@ struct percpu_rw_semaphore {
#define DEFINE_STATIC_PERCPU_RWSEM(name) \
static DEFINE_PER_CPU(unsigned int, __percpu_rwsem_rc_##name); \
static struct percpu_rw_semaphore name = { \
.rss = __RCU_SYNC_INITIALIZER(name.rss, RCU_SCHED_SYNC), \
.rss = __RCU_SYNC_INITIALIZER(name.rss), \
.read_count = &__percpu_rwsem_rc_##name, \
.rw_sem = __RWSEM_INITIALIZER(name.rw_sem), \
.writer = __RCUWAIT_INITIALIZER(name.writer), \

36
include/linux/rcu_sync.h
View File

@ -13,8 +13,6 @@
#include <linux/wait.h>
#include <linux/rcupdate.h>
enum rcu_sync_type { RCU_SYNC, RCU_SCHED_SYNC, RCU_BH_SYNC };
/* Structure to mediate between updaters and fastpath-using readers. */
struct rcu_sync {
int gp_state;
@ -23,52 +21,38 @@ struct rcu_sync {
int cb_state;
struct rcu_head cb_head;
enum rcu_sync_type gp_type;
};
extern void rcu_sync_lockdep_assert(struct rcu_sync *);
/**
* rcu_sync_is_idle() - Are readers permitted to use their fastpaths?
* @rsp: Pointer to rcu_sync structure to use for synchronization
*
* Returns true if readers are permitted to use their fastpaths.
* Must be invoked within an RCU read-side critical section whose
* flavor matches that of the rcu_sync struture.
* Returns true if readers are permitted to use their fastpaths. Must be
* invoked within some flavor of RCU read-side critical section.
*/
static inline bool rcu_sync_is_idle(struct rcu_sync *rsp)
{
#ifdef CONFIG_PROVE_RCU
rcu_sync_lockdep_assert(rsp);
#endif
RCU_LOCKDEP_WARN(!rcu_read_lock_held() &&
!rcu_read_lock_bh_held() &&
!rcu_read_lock_sched_held(),
"suspicious rcu_sync_is_idle() usage");
return !rsp->gp_state; /* GP_IDLE */
}
extern void rcu_sync_init(struct rcu_sync *, enum rcu_sync_type);
extern void rcu_sync_init(struct rcu_sync *);
extern void rcu_sync_enter_start(struct rcu_sync *);
extern void rcu_sync_enter(struct rcu_sync *);
extern void rcu_sync_exit(struct rcu_sync *);
extern void rcu_sync_dtor(struct rcu_sync *);
#define __RCU_SYNC_INITIALIZER(name, type) { \
#define __RCU_SYNC_INITIALIZER(name) { \
.gp_state = 0, \
.gp_count = 0, \
.gp_wait = __WAIT_QUEUE_HEAD_INITIALIZER(name.gp_wait), \
.cb_state = 0, \
.gp_type = type, \
}
#define __DEFINE_RCU_SYNC(name, type) \
struct rcu_sync_struct name = __RCU_SYNC_INITIALIZER(name, type)
#define DEFINE_RCU_SYNC(name) \
__DEFINE_RCU_SYNC(name, RCU_SYNC)
#define DEFINE_RCU_SCHED_SYNC(name) \
__DEFINE_RCU_SYNC(name, RCU_SCHED_SYNC)
#define DEFINE_RCU_BH_SYNC(name) \
__DEFINE_RCU_SYNC(name, RCU_BH_SYNC)
#define DEFINE_RCU_SYNC(name) \
struct rcu_sync name = __RCU_SYNC_INITIALIZER(name)
#endif /* _LINUX_RCU_SYNC_H_ */

2
kernel/locking/percpu-rwsem.c
View File

@ -17,7 +17,7 @@ int __percpu_init_rwsem(struct percpu_rw_semaphore *sem,
return -ENOMEM;
/* ->rw_sem represents the whole percpu_rw_semaphore for lockdep */
rcu_sync_init(&sem->rss, RCU_SCHED_SYNC);
rcu_sync_init(&sem->rss);
__init_rwsem(&sem->rw_sem, name, rwsem_key);
rcuwait_init(&sem->writer);
sem->readers_block = 0;

55
kernel/rcu/sync.c
View File

@ -10,65 +10,20 @@
#include <linux/rcu_sync.h>
#include <linux/sched.h>
#ifdef CONFIG_PROVE_RCU
#define __INIT_HELD(func) .held = func,
#else
#define __INIT_HELD(func)
#endif
static const struct {
void (*sync)(void);
void (*call)(struct rcu_head *, void (*)(struct rcu_head *));
void (*wait)(void);
#ifdef CONFIG_PROVE_RCU
int (*held)(void);
#endif
} gp_ops[] = {
[RCU_SYNC] = {
.sync = synchronize_rcu,
.call = call_rcu,
.wait = rcu_barrier,
__INIT_HELD(rcu_read_lock_held)
},
[RCU_SCHED_SYNC] = {
.sync = synchronize_rcu,
.call = call_rcu,
.wait = rcu_barrier,
__INIT_HELD(rcu_read_lock_sched_held)
},
[RCU_BH_SYNC] = {
.sync = synchronize_rcu,
.call = call_rcu,
.wait = rcu_barrier,
__INIT_HELD(rcu_read_lock_bh_held)
},
};
enum { GP_IDLE = 0, GP_PENDING, GP_PASSED };
enum { CB_IDLE = 0, CB_PENDING, CB_REPLAY };
#define rss_lock gp_wait.lock
#ifdef CONFIG_PROVE_RCU
void rcu_sync_lockdep_assert(struct rcu_sync *rsp)
{
RCU_LOCKDEP_WARN(!gp_ops[rsp->gp_type].held(),
"suspicious rcu_sync_is_idle() usage");
}
EXPORT_SYMBOL_GPL(rcu_sync_lockdep_assert);
#endif
/**
* rcu_sync_init() - Initialize an rcu_sync structure
* @rsp: Pointer to rcu_sync structure to be initialized
* @type: Flavor of RCU with which to synchronize rcu_sync structure
*/
void rcu_sync_init(struct rcu_sync *rsp, enum rcu_sync_type type)
void rcu_sync_init(struct rcu_sync *rsp)
{
memset(rsp, 0, sizeof(*rsp));
init_waitqueue_head(&rsp->gp_wait);
rsp->gp_type = type;
}
/**
@ -114,7 +69,7 @@ void rcu_sync_enter(struct rcu_sync *rsp)
WARN_ON_ONCE(need_wait && need_sync);
if (need_sync) {
gp_ops[rsp->gp_type].sync();
synchronize_rcu();
rsp->gp_state = GP_PASSED;
wake_up_all(&rsp->gp_wait);
} else if (need_wait) {
@ -167,7 +122,7 @@ static void rcu_sync_func(struct rcu_head *rhp)
* to catch a later GP.
*/
rsp->cb_state = CB_PENDING;
gp_ops[rsp->gp_type].call(&rsp->cb_head, rcu_sync_func);
call_rcu(&rsp->cb_head, rcu_sync_func);
} else {
/*
* We're at least a GP after rcu_sync_exit(); eveybody will now
@ -195,7 +150,7 @@ void rcu_sync_exit(struct rcu_sync *rsp)
if (!--rsp->gp_count) {
if (rsp->cb_state == CB_IDLE) {
rsp->cb_state = CB_PENDING;
gp_ops[rsp->gp_type].call(&rsp->cb_head, rcu_sync_func);
call_rcu(&rsp->cb_head, rcu_sync_func);
} else if (rsp->cb_state == CB_PENDING) {
rsp->cb_state = CB_REPLAY;
}
@ -220,7 +175,7 @@ void rcu_sync_dtor(struct rcu_sync *rsp)
spin_unlock_irq(&rsp->rss_lock);
if (cb_state != CB_IDLE) {
gp_ops[rsp->gp_type].wait();
rcu_barrier();
WARN_ON_ONCE(rsp->cb_state != CB_IDLE);
}
}