diff options
Diffstat (limited to 'kernel/rcuclassic.c')
-rw-r--r-- | kernel/rcuclassic.c | 177 |
1 files changed, 104 insertions, 73 deletions
diff --git a/kernel/rcuclassic.c b/kernel/rcuclassic.c index aad93cdc9f68..d4271146a9bd 100644 --- a/kernel/rcuclassic.c +++ b/kernel/rcuclassic.c @@ -60,12 +60,14 @@ EXPORT_SYMBOL_GPL(rcu_lock_map); static struct rcu_ctrlblk rcu_ctrlblk = { .cur = -300, .completed = -300, + .pending = -300, .lock = __SPIN_LOCK_UNLOCKED(&rcu_ctrlblk.lock), .cpumask = CPU_MASK_NONE, }; static struct rcu_ctrlblk rcu_bh_ctrlblk = { .cur = -300, .completed = -300, + .pending = -300, .lock = __SPIN_LOCK_UNLOCKED(&rcu_bh_ctrlblk.lock), .cpumask = CPU_MASK_NONE, }; @@ -118,6 +120,43 @@ static inline void force_quiescent_state(struct rcu_data *rdp, } #endif +static void __call_rcu(struct rcu_head *head, struct rcu_ctrlblk *rcp, + struct rcu_data *rdp) +{ + long batch; + smp_mb(); /* reads the most recently updated value of rcu->cur. */ + + /* + * Determine the batch number of this callback. + * + * Using ACCESS_ONCE to avoid the following error when gcc eliminates + * local variable "batch" and emits codes like this: + * 1) rdp->batch = rcp->cur + 1 # gets old value + * ...... + * 2)rcu_batch_after(rcp->cur + 1, rdp->batch) # gets new value + * then [*nxttail[0], *nxttail[1]) may contain callbacks + * that batch# = rdp->batch, see the comment of struct rcu_data. + */ + batch = ACCESS_ONCE(rcp->cur) + 1; + + if (rdp->nxtlist && rcu_batch_after(batch, rdp->batch)) { + /* process callbacks */ + rdp->nxttail[0] = rdp->nxttail[1]; + rdp->nxttail[1] = rdp->nxttail[2]; + if (rcu_batch_after(batch - 1, rdp->batch)) + rdp->nxttail[0] = rdp->nxttail[2]; + } + + rdp->batch = batch; + *rdp->nxttail[2] = head; + rdp->nxttail[2] = &head->next; + + if (unlikely(++rdp->qlen > qhimark)) { + rdp->blimit = INT_MAX; + force_quiescent_state(rdp, &rcu_ctrlblk); + } +} + /** * call_rcu - Queue an RCU callback for invocation after a grace period. * @head: structure to be used for queueing the RCU updates. @@ -133,18 +172,11 @@ void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) { unsigned long flags; - struct rcu_data *rdp; head->func = func; head->next = NULL; local_irq_save(flags); - rdp = &__get_cpu_var(rcu_data); - *rdp->nxttail = head; - rdp->nxttail = &head->next; - if (unlikely(++rdp->qlen > qhimark)) { - rdp->blimit = INT_MAX; - force_quiescent_state(rdp, &rcu_ctrlblk); - } + __call_rcu(head, &rcu_ctrlblk, &__get_cpu_var(rcu_data)); local_irq_restore(flags); } EXPORT_SYMBOL_GPL(call_rcu); @@ -169,20 +201,11 @@ void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) { unsigned long flags; - struct rcu_data *rdp; head->func = func; head->next = NULL; local_irq_save(flags); - rdp = &__get_cpu_var(rcu_bh_data); - *rdp->nxttail = head; - rdp->nxttail = &head->next; - - if (unlikely(++rdp->qlen > qhimark)) { - rdp->blimit = INT_MAX; - force_quiescent_state(rdp, &rcu_bh_ctrlblk); - } - + __call_rcu(head, &rcu_bh_ctrlblk, &__get_cpu_var(rcu_bh_data)); local_irq_restore(flags); } EXPORT_SYMBOL_GPL(call_rcu_bh); @@ -211,12 +234,6 @@ EXPORT_SYMBOL_GPL(rcu_batches_completed_bh); static inline void raise_rcu_softirq(void) { raise_softirq(RCU_SOFTIRQ); - /* - * The smp_mb() here is required to ensure that this cpu's - * __rcu_process_callbacks() reads the most recently updated - * value of rcu->cur. - */ - smp_mb(); } /* @@ -276,14 +293,8 @@ static void rcu_do_batch(struct rcu_data *rdp) */ static void rcu_start_batch(struct rcu_ctrlblk *rcp) { - if (rcp->next_pending && + if (rcp->cur != rcp->pending && rcp->completed == rcp->cur) { - rcp->next_pending = 0; - /* - * next_pending == 0 must be visible in - * __rcu_process_callbacks() before it can see new value of cur. - */ - smp_wmb(); rcp->cur++; /* @@ -364,13 +375,15 @@ static void rcu_check_quiescent_state(struct rcu_ctrlblk *rcp, * which is dead and hence not processing interrupts. */ static void rcu_move_batch(struct rcu_data *this_rdp, struct rcu_head *list, - struct rcu_head **tail) + struct rcu_head **tail, long batch) { - local_irq_disable(); - *this_rdp->nxttail = list; - if (list) - this_rdp->nxttail = tail; - local_irq_enable(); + if (list) { + local_irq_disable(); + this_rdp->batch = batch; + *this_rdp->nxttail[2] = list; + this_rdp->nxttail[2] = tail; + local_irq_enable(); + } } static void __rcu_offline_cpu(struct rcu_data *this_rdp, @@ -384,9 +397,9 @@ static void __rcu_offline_cpu(struct rcu_data *this_rdp, if (rcp->cur != rcp->completed) cpu_quiet(rdp->cpu, rcp); spin_unlock_bh(&rcp->lock); - rcu_move_batch(this_rdp, rdp->donelist, rdp->donetail); - rcu_move_batch(this_rdp, rdp->curlist, rdp->curtail); - rcu_move_batch(this_rdp, rdp->nxtlist, rdp->nxttail); + /* spin_lock implies smp_mb() */ + rcu_move_batch(this_rdp, rdp->donelist, rdp->donetail, rcp->cur + 1); + rcu_move_batch(this_rdp, rdp->nxtlist, rdp->nxttail[2], rcp->cur + 1); local_irq_disable(); this_rdp->qlen += rdp->qlen; @@ -420,37 +433,45 @@ static void rcu_offline_cpu(int cpu) static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp, struct rcu_data *rdp) { - if (rdp->curlist && !rcu_batch_before(rcp->completed, rdp->batch)) { - *rdp->donetail = rdp->curlist; - rdp->donetail = rdp->curtail; - rdp->curlist = NULL; - rdp->curtail = &rdp->curlist; - } - - if (rdp->nxtlist && !rdp->curlist) { + if (rdp->nxtlist) { local_irq_disable(); - rdp->curlist = rdp->nxtlist; - rdp->curtail = rdp->nxttail; - rdp->nxtlist = NULL; - rdp->nxttail = &rdp->nxtlist; - local_irq_enable(); /* - * start the next batch of callbacks + * move the other grace-period-completed entries to + * [rdp->nxtlist, *rdp->nxttail[0]) temporarily */ + if (!rcu_batch_before(rcp->completed, rdp->batch)) + rdp->nxttail[0] = rdp->nxttail[1] = rdp->nxttail[2]; + else if (!rcu_batch_before(rcp->completed, rdp->batch - 1)) + rdp->nxttail[0] = rdp->nxttail[1]; - /* determine batch number */ - rdp->batch = rcp->cur + 1; - /* see the comment and corresponding wmb() in - * the rcu_start_batch() + /* + * the grace period for entries in + * [rdp->nxtlist, *rdp->nxttail[0]) has completed and + * move these entries to donelist */ - smp_rmb(); + if (rdp->nxttail[0] != &rdp->nxtlist) { + *rdp->donetail = rdp->nxtlist; + rdp->donetail = rdp->nxttail[0]; + rdp->nxtlist = *rdp->nxttail[0]; + *rdp->donetail = NULL; + + if (rdp->nxttail[1] == rdp->nxttail[0]) + rdp->nxttail[1] = &rdp->nxtlist; + if (rdp->nxttail[2] == rdp->nxttail[0]) + rdp->nxttail[2] = &rdp->nxtlist; + rdp->nxttail[0] = &rdp->nxtlist; + } + + local_irq_enable(); - if (!rcp->next_pending) { + if (rcu_batch_after(rdp->batch, rcp->pending)) { /* and start it/schedule start if it's a new batch */ spin_lock(&rcp->lock); - rcp->next_pending = 1; - rcu_start_batch(rcp); + if (rcu_batch_after(rdp->batch, rcp->pending)) { + rcp->pending = rdp->batch; + rcu_start_batch(rcp); + } spin_unlock(&rcp->lock); } } @@ -468,15 +489,26 @@ static void rcu_process_callbacks(struct softirq_action *unused) static int __rcu_pending(struct rcu_ctrlblk *rcp, struct rcu_data *rdp) { - /* This cpu has pending rcu entries and the grace period - * for them has completed. - */ - if (rdp->curlist && !rcu_batch_before(rcp->completed, rdp->batch)) - return 1; + if (rdp->nxtlist) { + /* + * This cpu has pending rcu entries and the grace period + * for them has completed. + */ + if (!rcu_batch_before(rcp->completed, rdp->batch)) + return 1; + if (!rcu_batch_before(rcp->completed, rdp->batch - 1) && + rdp->nxttail[0] != rdp->nxttail[1]) + return 1; + if (rdp->nxttail[0] != &rdp->nxtlist) + return 1; - /* This cpu has no pending entries, but there are new entries */ - if (!rdp->curlist && rdp->nxtlist) - return 1; + /* + * This cpu has pending rcu entries and the new batch + * for then hasn't been started nor scheduled start + */ + if (rcu_batch_after(rdp->batch, rcp->pending)) + return 1; + } /* This cpu has finished callbacks to invoke */ if (rdp->donelist) @@ -512,7 +544,7 @@ int rcu_needs_cpu(int cpu) struct rcu_data *rdp = &per_cpu(rcu_data, cpu); struct rcu_data *rdp_bh = &per_cpu(rcu_bh_data, cpu); - return (!!rdp->curlist || !!rdp_bh->curlist || rcu_pending(cpu)); + return !!rdp->nxtlist || !!rdp_bh->nxtlist || rcu_pending(cpu); } void rcu_check_callbacks(int cpu, int user) @@ -559,8 +591,7 @@ static void rcu_init_percpu_data(int cpu, struct rcu_ctrlblk *rcp, struct rcu_data *rdp) { memset(rdp, 0, sizeof(*rdp)); - rdp->curtail = &rdp->curlist; - rdp->nxttail = &rdp->nxtlist; + rdp->nxttail[0] = rdp->nxttail[1] = rdp->nxttail[2] = &rdp->nxtlist; rdp->donetail = &rdp->donelist; rdp->quiescbatch = rcp->completed; rdp->qs_pending = 0; |