diff options
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/list.h | 10 | ||||
| -rw-r--r-- | include/linux/rculist.h | 10 | ||||
| -rw-r--r-- | include/linux/srcu.h | 34 | ||||
| -rw-r--r-- | include/linux/srcutree.h | 49 |
4 files changed, 74 insertions, 29 deletions
diff --git a/include/linux/list.h b/include/linux/list.h index 5bfda2f91fca..00ea8e5fb88b 100644 --- a/include/linux/list.h +++ b/include/linux/list.h @@ -709,16 +709,6 @@ static inline void list_splice_tail_init(struct list_head *list, for (pos = (head)->next; !list_is_head(pos, (head)); pos = pos->next) /** - * list_for_each_rcu - Iterate over a list in an RCU-safe fashion - * @pos: the &struct list_head to use as a loop cursor. - * @head: the head for your list. - */ -#define list_for_each_rcu(pos, head) \ - for (pos = rcu_dereference((head)->next); \ - !list_is_head(pos, (head)); \ - pos = rcu_dereference(pos->next)) - -/** * list_for_each_continue - continue iteration over a list * @pos: the &struct list_head to use as a loop cursor. * @head: the head for your list. diff --git a/include/linux/rculist.h b/include/linux/rculist.h index 1b11926ddd47..2abba7552605 100644 --- a/include/linux/rculist.h +++ b/include/linux/rculist.h @@ -43,6 +43,16 @@ static inline void INIT_LIST_HEAD_RCU(struct list_head *list) #define list_bidir_prev_rcu(list) (*((struct list_head __rcu **)(&(list)->prev))) /** + * list_for_each_rcu - Iterate over a list in an RCU-safe fashion + * @pos: the &struct list_head to use as a loop cursor. + * @head: the head for your list. + */ +#define list_for_each_rcu(pos, head) \ + for (pos = rcu_dereference((head)->next); \ + !list_is_head(pos, (head)); \ + pos = rcu_dereference(pos->next)) + +/** * list_tail_rcu - returns the prev pointer of the head of the list * @head: the head of the list * diff --git a/include/linux/srcu.h b/include/linux/srcu.h index f179700fecaf..ada65b58bc4c 100644 --- a/include/linux/srcu.h +++ b/include/linux/srcu.h @@ -275,12 +275,27 @@ static inline struct srcu_ctr __percpu *srcu_read_lock_fast(struct srcu_struct * { struct srcu_ctr __percpu *retval; + RCU_LOCKDEP_WARN(!rcu_is_watching(), "RCU must be watching srcu_read_lock_fast()."); srcu_check_read_flavor_force(ssp, SRCU_READ_FLAVOR_FAST); retval = __srcu_read_lock_fast(ssp); rcu_try_lock_acquire(&ssp->dep_map); return retval; } +/* + * Used by tracing, cannot be traced and cannot call lockdep. + * See srcu_read_lock_fast() for more information. + */ +static inline struct srcu_ctr __percpu *srcu_read_lock_fast_notrace(struct srcu_struct *ssp) + __acquires(ssp) +{ + struct srcu_ctr __percpu *retval; + + srcu_check_read_flavor_force(ssp, SRCU_READ_FLAVOR_FAST); + retval = __srcu_read_lock_fast(ssp); + return retval; +} + /** * srcu_down_read_fast - register a new reader for an SRCU-protected structure. * @ssp: srcu_struct in which to register the new reader. @@ -295,6 +310,7 @@ static inline struct srcu_ctr __percpu *srcu_read_lock_fast(struct srcu_struct * static inline struct srcu_ctr __percpu *srcu_down_read_fast(struct srcu_struct *ssp) __acquires(ssp) { WARN_ON_ONCE(IS_ENABLED(CONFIG_PROVE_RCU) && in_nmi()); + RCU_LOCKDEP_WARN(!rcu_is_watching(), "RCU must be watching srcu_down_read_fast()."); srcu_check_read_flavor_force(ssp, SRCU_READ_FLAVOR_FAST); return __srcu_read_lock_fast(ssp); } @@ -389,6 +405,18 @@ static inline void srcu_read_unlock_fast(struct srcu_struct *ssp, struct srcu_ct srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_FAST); srcu_lock_release(&ssp->dep_map); __srcu_read_unlock_fast(ssp, scp); + RCU_LOCKDEP_WARN(!rcu_is_watching(), "RCU must be watching srcu_read_unlock_fast()."); +} + +/* + * Used by tracing, cannot be traced and cannot call lockdep. + * See srcu_read_unlock_fast() for more information. + */ +static inline void srcu_read_unlock_fast_notrace(struct srcu_struct *ssp, + struct srcu_ctr __percpu *scp) __releases(ssp) +{ + srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_FAST); + __srcu_read_unlock_fast(ssp, scp); } /** @@ -405,6 +433,7 @@ static inline void srcu_up_read_fast(struct srcu_struct *ssp, struct srcu_ctr __ WARN_ON_ONCE(IS_ENABLED(CONFIG_PROVE_RCU) && in_nmi()); srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_FAST); __srcu_read_unlock_fast(ssp, scp); + RCU_LOCKDEP_WARN(!rcu_is_watching(), "RCU must be watching srcu_up_read_fast()."); } /** @@ -486,4 +515,9 @@ DEFINE_LOCK_GUARD_1(srcu_fast, struct srcu_struct, srcu_read_unlock_fast(_T->lock, _T->scp), struct srcu_ctr __percpu *scp) +DEFINE_LOCK_GUARD_1(srcu_fast_notrace, struct srcu_struct, + _T->scp = srcu_read_lock_fast_notrace(_T->lock), + srcu_read_unlock_fast_notrace(_T->lock, _T->scp), + struct srcu_ctr __percpu *scp) + #endif diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h index bf44d8d1e69e..42098e0fa0b7 100644 --- a/include/linux/srcutree.h +++ b/include/linux/srcutree.h @@ -232,23 +232,40 @@ static inline struct srcu_ctr __percpu *__srcu_ctr_to_ptr(struct srcu_struct *ss * srcu_read_unlock_fast(). * * Note that both this_cpu_inc() and atomic_long_inc() are RCU read-side - * critical sections either because they disables interrupts, because they - * are a single instruction, or because they are a read-modify-write atomic - * operation, depending on the whims of the architecture. + * critical sections either because they disables interrupts, because + * they are a single instruction, or because they are read-modify-write + * atomic operations, depending on the whims of the architecture. + * This matters because the SRCU-fast grace-period mechanism uses either + * synchronize_rcu() or synchronize_rcu_expedited(), that is, RCU, + * *not* SRCU, in order to eliminate the need for the read-side smp_mb() + * invocations that are used by srcu_read_lock() and srcu_read_unlock(). + * The __srcu_read_unlock_fast() function also relies on this same RCU + * (again, *not* SRCU) trick to eliminate the need for smp_mb(). + * + * The key point behind this RCU trick is that if any part of a given + * RCU reader precedes the beginning of a given RCU grace period, then + * the entirety of that RCU reader and everything preceding it happens + * before the end of that same RCU grace period. Similarly, if any part + * of a given RCU reader follows the end of a given RCU grace period, + * then the entirety of that RCU reader and everything following it + * happens after the beginning of that same RCU grace period. Therefore, + * the operations labeled Y in __srcu_read_lock_fast() and those labeled Z + * in __srcu_read_unlock_fast() are ordered against the corresponding SRCU + * read-side critical section from the viewpoint of the SRCU grace period. + * This is all the ordering that is required, hence no calls to smp_mb(). * * This means that __srcu_read_lock_fast() is not all that fast * on architectures that support NMIs but do not supply NMI-safe * implementations of this_cpu_inc(). */ -static inline struct srcu_ctr __percpu *__srcu_read_lock_fast(struct srcu_struct *ssp) +static inline struct srcu_ctr __percpu notrace *__srcu_read_lock_fast(struct srcu_struct *ssp) { struct srcu_ctr __percpu *scp = READ_ONCE(ssp->srcu_ctrp); - RCU_LOCKDEP_WARN(!rcu_is_watching(), "RCU must be watching srcu_read_lock_fast()."); if (!IS_ENABLED(CONFIG_NEED_SRCU_NMI_SAFE)) - this_cpu_inc(scp->srcu_locks.counter); /* Y */ + this_cpu_inc(scp->srcu_locks.counter); // Y, and implicit RCU reader. else - atomic_long_inc(raw_cpu_ptr(&scp->srcu_locks)); /* Z */ + atomic_long_inc(raw_cpu_ptr(&scp->srcu_locks)); // Y, and implicit RCU reader. barrier(); /* Avoid leaking the critical section. */ return scp; } @@ -259,23 +276,17 @@ static inline struct srcu_ctr __percpu *__srcu_read_lock_fast(struct srcu_struct * different CPU than that which was incremented by the corresponding * srcu_read_lock_fast(), but it must be within the same task. * - * Note that both this_cpu_inc() and atomic_long_inc() are RCU read-side - * critical sections either because they disables interrupts, because they - * are a single instruction, or because they are a read-modify-write atomic - * operation, depending on the whims of the architecture. - * - * This means that __srcu_read_unlock_fast() is not all that fast - * on architectures that support NMIs but do not supply NMI-safe - * implementations of this_cpu_inc(). + * Please see the __srcu_read_lock_fast() function's header comment for + * information on implicit RCU readers and NMI safety. */ -static inline void __srcu_read_unlock_fast(struct srcu_struct *ssp, struct srcu_ctr __percpu *scp) +static inline void notrace +__srcu_read_unlock_fast(struct srcu_struct *ssp, struct srcu_ctr __percpu *scp) { barrier(); /* Avoid leaking the critical section. */ if (!IS_ENABLED(CONFIG_NEED_SRCU_NMI_SAFE)) - this_cpu_inc(scp->srcu_unlocks.counter); /* Z */ + this_cpu_inc(scp->srcu_unlocks.counter); // Z, and implicit RCU reader. else - atomic_long_inc(raw_cpu_ptr(&scp->srcu_unlocks)); /* Z */ - RCU_LOCKDEP_WARN(!rcu_is_watching(), "RCU must be watching srcu_read_unlock_fast()."); + atomic_long_inc(raw_cpu_ptr(&scp->srcu_unlocks)); // Z, and implicit RCU reader. } void __srcu_check_read_flavor(struct srcu_struct *ssp, int read_flavor); |