diff options
| -rw-r--r-- | include/linux/rcupdate.h | 2 | ||||
| -rw-r--r-- | include/linux/srcu.h | 3 | ||||
| -rw-r--r-- | include/linux/srcutiny.h | 1 | ||||
| -rw-r--r-- | kernel/rcu/srcutiny.c | 55 |
4 files changed, 59 insertions, 2 deletions
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index de0826411311..e09c0d87b3c3 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -33,6 +33,8 @@ #define ULONG_CMP_GE(a, b) (ULONG_MAX / 2 >= (a) - (b)) #define ULONG_CMP_LT(a, b) (ULONG_MAX / 2 < (a) - (b)) #define ulong2long(a) (*(long *)(&(a))) +#define USHORT_CMP_GE(a, b) (USHRT_MAX / 2 >= (unsigned short)((a) - (b))) +#define USHORT_CMP_LT(a, b) (USHRT_MAX / 2 < (unsigned short)((a) - (b))) /* Exported common interfaces */ void call_rcu(struct rcu_head *head, rcu_callback_t func); diff --git a/include/linux/srcu.h b/include/linux/srcu.h index e432cc92c73d..a0895bbf71ce 100644 --- a/include/linux/srcu.h +++ b/include/linux/srcu.h @@ -60,6 +60,9 @@ void cleanup_srcu_struct(struct srcu_struct *ssp); int __srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp); void __srcu_read_unlock(struct srcu_struct *ssp, int idx) __releases(ssp); void synchronize_srcu(struct srcu_struct *ssp); +unsigned long get_state_synchronize_srcu(struct srcu_struct *ssp); +unsigned long start_poll_synchronize_srcu(struct srcu_struct *ssp); +bool poll_state_synchronize_srcu(struct srcu_struct *ssp, unsigned long cookie); #ifdef CONFIG_DEBUG_LOCK_ALLOC diff --git a/include/linux/srcutiny.h b/include/linux/srcutiny.h index b8b42d0a24f1..0e0cf4d6a72a 100644 --- a/include/linux/srcutiny.h +++ b/include/linux/srcutiny.h @@ -16,6 +16,7 @@ struct srcu_struct { short srcu_lock_nesting[2]; /* srcu_read_lock() nesting depth. */ unsigned short srcu_idx; /* Current reader array element in bit 0x2. */ + unsigned short srcu_idx_max; /* Furthest future srcu_idx request. */ u8 srcu_gp_running; /* GP workqueue running? */ u8 srcu_gp_waiting; /* GP waiting for readers? */ struct swait_queue_head srcu_wq; diff --git a/kernel/rcu/srcutiny.c b/kernel/rcu/srcutiny.c index 3bac1db85a85..26344dc6483b 100644 --- a/kernel/rcu/srcutiny.c +++ b/kernel/rcu/srcutiny.c @@ -34,6 +34,7 @@ static int init_srcu_struct_fields(struct srcu_struct *ssp) ssp->srcu_gp_running = false; ssp->srcu_gp_waiting = false; ssp->srcu_idx = 0; + ssp->srcu_idx_max = 0; INIT_WORK(&ssp->srcu_work, srcu_drive_gp); INIT_LIST_HEAD(&ssp->srcu_work.entry); return 0; @@ -84,6 +85,8 @@ void cleanup_srcu_struct(struct srcu_struct *ssp) WARN_ON(ssp->srcu_gp_waiting); WARN_ON(ssp->srcu_cb_head); WARN_ON(&ssp->srcu_cb_head != ssp->srcu_cb_tail); + WARN_ON(ssp->srcu_idx != ssp->srcu_idx_max); + WARN_ON(ssp->srcu_idx & 0x1); } EXPORT_SYMBOL_GPL(cleanup_srcu_struct); @@ -114,7 +117,7 @@ void srcu_drive_gp(struct work_struct *wp) struct srcu_struct *ssp; ssp = container_of(wp, struct srcu_struct, srcu_work); - if (ssp->srcu_gp_running || !READ_ONCE(ssp->srcu_cb_head)) + if (ssp->srcu_gp_running || USHORT_CMP_GE(ssp->srcu_idx, READ_ONCE(ssp->srcu_idx_max))) return; /* Already running or nothing to do. */ /* Remove recently arrived callbacks and wait for readers. */ @@ -147,13 +150,19 @@ void srcu_drive_gp(struct work_struct *wp) * straighten that out. */ WRITE_ONCE(ssp->srcu_gp_running, false); - if (READ_ONCE(ssp->srcu_cb_head)) + if (USHORT_CMP_LT(ssp->srcu_idx, READ_ONCE(ssp->srcu_idx_max))) schedule_work(&ssp->srcu_work); } EXPORT_SYMBOL_GPL(srcu_drive_gp); static void srcu_gp_start_if_needed(struct srcu_struct *ssp) { + unsigned short cookie; + + cookie = get_state_synchronize_srcu(ssp); + if (USHORT_CMP_GE(READ_ONCE(ssp->srcu_idx_max), cookie)) + return; + WRITE_ONCE(ssp->srcu_idx_max, cookie); if (!READ_ONCE(ssp->srcu_gp_running)) { if (likely(srcu_init_done)) schedule_work(&ssp->srcu_work); @@ -196,6 +205,48 @@ void synchronize_srcu(struct srcu_struct *ssp) } EXPORT_SYMBOL_GPL(synchronize_srcu); +/* + * get_state_synchronize_srcu - Provide an end-of-grace-period cookie + */ +unsigned long get_state_synchronize_srcu(struct srcu_struct *ssp) +{ + unsigned long ret; + + barrier(); + ret = (READ_ONCE(ssp->srcu_idx) + 3) & ~0x1; + barrier(); + return ret & USHRT_MAX; +} +EXPORT_SYMBOL_GPL(get_state_synchronize_srcu); + +/* + * start_poll_synchronize_srcu - Provide cookie and start grace period + * + * The difference between this and get_state_synchronize_srcu() is that + * this function ensures that the poll_state_synchronize_srcu() will + * eventually return the value true. + */ +unsigned long start_poll_synchronize_srcu(struct srcu_struct *ssp) +{ + unsigned long ret = get_state_synchronize_srcu(ssp); + + srcu_gp_start_if_needed(ssp); + return ret; +} +EXPORT_SYMBOL_GPL(start_poll_synchronize_srcu); + +/* + * poll_state_synchronize_srcu - Has cookie's grace period ended? + */ +bool poll_state_synchronize_srcu(struct srcu_struct *ssp, unsigned long cookie) +{ + bool ret = USHORT_CMP_GE(READ_ONCE(ssp->srcu_idx), cookie); + + barrier(); + return ret; +} +EXPORT_SYMBOL_GPL(poll_state_synchronize_srcu); + /* Lockdep diagnostics. */ void __init rcu_scheduler_starting(void) { |