X-Git-Url: http://git.onelab.eu/?a=blobdiff_plain;f=kernel%2Frcupdate.c;h=f0ae3c3c013eb6053a6db0e0f955c926c90e37ab;hb=6a77f38946aaee1cd85eeec6cf4229b204c15071;hp=b331fe3f64e9904d65dbc2e2dc96a61f9a5e7dcb;hpb=9bf4aaab3e101692164d49b7ca357651eb691cb6;p=linux-2.6.git diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c index b331fe3f6..f0ae3c3c0 100644 --- a/kernel/rcupdate.c +++ b/kernel/rcupdate.c @@ -17,9 +17,10 @@ * * Copyright (C) IBM Corporation, 2001 * - * Author: Dipankar Sarma + * Authors: Dipankar Sarma + * Manfred Spraul * - * Based on the original work by Paul McKenney + * Based on the original work by Paul McKenney * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. * Papers: * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf @@ -37,9 +38,10 @@ #include #include #include -#include +#include #include #include +#include #include #include #include @@ -47,45 +49,83 @@ /* Definition for rcupdate control block. */ struct rcu_ctrlblk rcu_ctrlblk = - { .cur = -300, .completed = -300 , .lock = SEQCNT_ZERO }; + { .cur = -300, .completed = -300 }; +struct rcu_ctrlblk rcu_bh_ctrlblk = + { .cur = -300, .completed = -300 }; /* Bookkeeping of the progress of the grace period */ -struct { - spinlock_t mutex; /* Guard this struct and writes to rcu_ctrlblk */ - cpumask_t rcu_cpu_mask; /* CPUs that need to switch in order */ +struct rcu_state { + spinlock_t lock; /* Guard this struct and writes to rcu_ctrlblk */ + cpumask_t cpumask; /* CPUs that need to switch in order */ /* for current batch to proceed. */ -} rcu_state ____cacheline_maxaligned_in_smp = - {.mutex = SPIN_LOCK_UNLOCKED, .rcu_cpu_mask = CPU_MASK_NONE }; +}; +static struct rcu_state rcu_state ____cacheline_maxaligned_in_smp = + {.lock = SPIN_LOCK_UNLOCKED, .cpumask = CPU_MASK_NONE }; +static struct rcu_state rcu_bh_state ____cacheline_maxaligned_in_smp = + {.lock = SPIN_LOCK_UNLOCKED, .cpumask = CPU_MASK_NONE }; DEFINE_PER_CPU(struct rcu_data, rcu_data) = { 0L }; +DEFINE_PER_CPU(struct rcu_data, rcu_bh_data) = { 0L }; /* Fake initialization required by compiler */ static DEFINE_PER_CPU(struct tasklet_struct, rcu_tasklet) = {NULL}; -#define RCU_tasklet(cpu) (per_cpu(rcu_tasklet, cpu)) +static int maxbatch = 10; /** - * call_rcu - Queue an RCU update request. + * call_rcu - Queue an RCU callback for invocation after a grace period. * @head: structure to be used for queueing the RCU updates. * @func: actual update function to be invoked after the grace period * - * The update function will be invoked as soon as all CPUs have performed - * a context switch or been seen in the idle loop or in a user process. - * The read-side of critical section that use call_rcu() for updation must - * be protected by rcu_read_lock()/rcu_read_unlock(). + * The update function will be invoked some time after a full grace + * period elapses, in other words after all currently executing RCU + * read-side critical sections have completed. RCU read-side critical + * sections are delimited by rcu_read_lock() and rcu_read_unlock(), + * and may be nested. */ void fastcall call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) { - int cpu; unsigned long flags; + struct rcu_data *rdp; head->func = func; head->next = NULL; local_irq_save(flags); - cpu = smp_processor_id(); - *RCU_nxttail(cpu) = head; - RCU_nxttail(cpu) = &head->next; + rdp = &__get_cpu_var(rcu_data); + *rdp->nxttail = head; + rdp->nxttail = &head->next; + local_irq_restore(flags); +} + +/** + * call_rcu_bh - Queue an RCU for invocation after a quicker grace period. + * @head: structure to be used for queueing the RCU updates. + * @func: actual update function to be invoked after the grace period + * + * The update function will be invoked some time after a full grace + * period elapses, in other words after all currently executing RCU + * read-side critical sections have completed. call_rcu_bh() assumes + * that the read-side critical sections end on completion of a softirq + * handler. This means that read-side critical sections in process + * context must not be interrupted by softirqs. This interface is to be + * used when most of the read-side critical sections are in softirq context. + * RCU read-side critical sections are delimited by rcu_read_lock() and + * rcu_read_unlock(), * if in interrupt context or rcu_read_lock_bh() + * and rcu_read_unlock_bh(), if in process context. These may be nested. + */ +void fastcall 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; local_irq_restore(flags); } @@ -93,15 +133,23 @@ void fastcall call_rcu(struct rcu_head *head, * Invoke the completed RCU callbacks. They are expected to be in * a per-cpu list. */ -static void rcu_do_batch(struct rcu_head *list) +static void rcu_do_batch(struct rcu_data *rdp) { - struct rcu_head *next; + struct rcu_head *next, *list; + int count = 0; + list = rdp->donelist; while (list) { - next = list->next; + next = rdp->donelist = list->next; list->func(list); list = next; + if (++count >= maxbatch) + break; } + if (!rdp->donelist) + rdp->donetail = &rdp->donelist; + else + tasklet_schedule(&per_cpu(rcu_tasklet, rdp->cpu)); } /* @@ -109,15 +157,15 @@ static void rcu_do_batch(struct rcu_head *list) * The grace period handling consists out of two steps: * - A new grace period is started. * This is done by rcu_start_batch. The start is not broadcasted to - * all cpus, they must pick this up by comparing rcu_ctrlblk.cur with - * RCU_quiescbatch(cpu). All cpus are recorded in the - * rcu_state.rcu_cpu_mask bitmap. + * all cpus, they must pick this up by comparing rcp->cur with + * rdp->quiescbatch. All cpus are recorded in the + * rcu_state.cpumask bitmap. * - All cpus must go through a quiescent state. * Since the start of the grace period is not broadcasted, at least two * calls to rcu_check_quiescent_state are required: * The first call just notices that a new grace period is running. The * following calls check if there was a quiescent state since the beginning - * of the grace period. If so, it updates rcu_state.rcu_cpu_mask. If + * of the grace period. If so, it updates rcu_state.cpumask. If * the bitmap is empty, then the grace period is completed. * rcu_check_quiescent_state calls rcu_start_batch(0) to start the next grace * period (if necessary). @@ -125,22 +173,25 @@ static void rcu_do_batch(struct rcu_head *list) /* * Register a new batch of callbacks, and start it up if there is currently no * active batch and the batch to be registered has not already occurred. - * Caller must hold rcu_state.mutex. + * Caller must hold rcu_state.lock. */ -static void rcu_start_batch(int next_pending) +static void rcu_start_batch(struct rcu_ctrlblk *rcp, struct rcu_state *rsp, + int next_pending) { if (next_pending) - rcu_ctrlblk.next_pending = 1; + rcp->next_pending = 1; - if (rcu_ctrlblk.next_pending && - rcu_ctrlblk.completed == rcu_ctrlblk.cur) { + if (rcp->next_pending && + rcp->completed == rcp->cur) { /* Can't change, since spin lock held. */ - cpus_andnot(rcu_state.rcu_cpu_mask, cpu_online_map, - nohz_cpu_mask); - write_seqcount_begin(&rcu_ctrlblk.lock); - rcu_ctrlblk.next_pending = 0; - rcu_ctrlblk.cur++; - write_seqcount_end(&rcu_ctrlblk.lock); + cpus_andnot(rsp->cpumask, cpu_online_map, nohz_cpu_mask); + + 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++; } } @@ -149,13 +200,13 @@ static void rcu_start_batch(int next_pending) * Clear it from the cpu mask and complete the grace period if it was the last * cpu. Start another grace period if someone has further entries pending */ -static void cpu_quiet(int cpu) +static void cpu_quiet(int cpu, struct rcu_ctrlblk *rcp, struct rcu_state *rsp) { - cpu_clear(cpu, rcu_state.rcu_cpu_mask); - if (cpus_empty(rcu_state.rcu_cpu_mask)) { + cpu_clear(cpu, rsp->cpumask); + if (cpus_empty(rsp->cpumask)) { /* batch completed ! */ - rcu_ctrlblk.completed = rcu_ctrlblk.cur; - rcu_start_batch(0); + rcp->completed = rcp->cur; + rcu_start_batch(rcp, rsp, 0); } } @@ -164,15 +215,14 @@ static void cpu_quiet(int cpu) * switch). If so and if it already hasn't done so in this RCU * quiescent cycle, then indicate that it has done so. */ -static void rcu_check_quiescent_state(void) +static void rcu_check_quiescent_state(struct rcu_ctrlblk *rcp, + struct rcu_state *rsp, struct rcu_data *rdp) { - int cpu = smp_processor_id(); - - if (RCU_quiescbatch(cpu) != rcu_ctrlblk.cur) { - /* new grace period: record qsctr value. */ - RCU_qs_pending(cpu) = 1; - RCU_last_qsctr(cpu) = RCU_qsctr(cpu); - RCU_quiescbatch(cpu) = rcu_ctrlblk.cur; + if (rdp->quiescbatch != rcp->cur) { + /* start new grace period: */ + rdp->qs_pending = 1; + rdp->passed_quiesc = 0; + rdp->quiescbatch = rcp->cur; return; } @@ -180,27 +230,26 @@ static void rcu_check_quiescent_state(void) * qs_pending is checked instead of the actual bitmap to avoid * cacheline trashing. */ - if (!RCU_qs_pending(cpu)) + if (!rdp->qs_pending) return; /* - * Races with local timer interrupt - in the worst case - * we may miss one quiescent state of that CPU. That is - * tolerable. So no need to disable interrupts. + * Was there a quiescent state since the beginning of the grace + * period? If no, then exit and wait for the next call. */ - if (RCU_qsctr(cpu) == RCU_last_qsctr(cpu)) + if (!rdp->passed_quiesc) return; - RCU_qs_pending(cpu) = 0; + rdp->qs_pending = 0; - spin_lock(&rcu_state.mutex); + spin_lock(&rsp->lock); /* - * RCU_quiescbatch/batch.cur and the cpu bitmap can come out of sync + * rdp->quiescbatch/rcp->cur and the cpu bitmap can come out of sync * during cpu startup. Ignore the quiescent state. */ - if (likely(RCU_quiescbatch(cpu) == rcu_ctrlblk.cur)) - cpu_quiet(cpu); + if (likely(rdp->quiescbatch == rcp->cur)) + cpu_quiet(rdp->cpu, rcp, rsp); - spin_unlock(&rcu_state.mutex); + spin_unlock(&rsp->lock); } @@ -210,112 +259,139 @@ static void rcu_check_quiescent_state(void) * locking requirements, the list it's pulling from has to belong to a cpu * which is dead and hence not processing interrupts. */ -static void rcu_move_batch(struct rcu_head *list) +static void rcu_move_batch(struct rcu_data *this_rdp, struct rcu_head *list, + struct rcu_head **tail) { - int cpu; - local_irq_disable(); - - cpu = smp_processor_id(); - - while (list != NULL) { - *RCU_nxttail(cpu) = list; - RCU_nxttail(cpu) = &list->next; - list = list->next; - } + *this_rdp->nxttail = list; + if (list) + this_rdp->nxttail = tail; local_irq_enable(); } -static void rcu_offline_cpu(int cpu) +static void __rcu_offline_cpu(struct rcu_data *this_rdp, + struct rcu_ctrlblk *rcp, struct rcu_state *rsp, struct rcu_data *rdp) { /* if the cpu going offline owns the grace period * we can block indefinitely waiting for it, so flush * it here */ - spin_lock_bh(&rcu_state.mutex); - if (rcu_ctrlblk.cur != rcu_ctrlblk.completed) - cpu_quiet(cpu); - spin_unlock_bh(&rcu_state.mutex); - - rcu_move_batch(RCU_curlist(cpu)); - rcu_move_batch(RCU_nxtlist(cpu)); + spin_lock_bh(&rsp->lock); + if (rcp->cur != rcp->completed) + cpu_quiet(rdp->cpu, rcp, rsp); + spin_unlock_bh(&rsp->lock); + rcu_move_batch(this_rdp, rdp->curlist, rdp->curtail); + rcu_move_batch(this_rdp, rdp->nxtlist, rdp->nxttail); - tasklet_kill_immediate(&RCU_tasklet(cpu), cpu); +} +static void rcu_offline_cpu(int cpu) +{ + struct rcu_data *this_rdp = &get_cpu_var(rcu_data); + struct rcu_data *this_bh_rdp = &get_cpu_var(rcu_bh_data); + + __rcu_offline_cpu(this_rdp, &rcu_ctrlblk, &rcu_state, + &per_cpu(rcu_data, cpu)); + __rcu_offline_cpu(this_bh_rdp, &rcu_bh_ctrlblk, &rcu_bh_state, + &per_cpu(rcu_bh_data, cpu)); + put_cpu_var(rcu_data); + put_cpu_var(rcu_bh_data); + tasklet_kill_immediate(&per_cpu(rcu_tasklet, cpu), cpu); } -#endif +#else -void rcu_restart_cpu(int cpu) +static void rcu_offline_cpu(int cpu) { - spin_lock_bh(&rcu_state.mutex); - RCU_quiescbatch(cpu) = rcu_ctrlblk.completed; - RCU_qs_pending(cpu) = 0; - spin_unlock_bh(&rcu_state.mutex); } +#endif + /* * This does the RCU processing work from tasklet context. */ -static void rcu_process_callbacks(unsigned long unused) +static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp, + struct rcu_state *rsp, struct rcu_data *rdp) { - int cpu = smp_processor_id(); - struct rcu_head *rcu_list = NULL; - - if (RCU_curlist(cpu) && - !rcu_batch_before(rcu_ctrlblk.completed, RCU_batch(cpu))) { - rcu_list = RCU_curlist(cpu); - RCU_curlist(cpu) = NULL; + 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; } local_irq_disable(); - if (RCU_nxtlist(cpu) && !RCU_curlist(cpu)) { - int next_pending, seq; - - RCU_curlist(cpu) = RCU_nxtlist(cpu); - RCU_nxtlist(cpu) = NULL; - RCU_nxttail(cpu) = &RCU_nxtlist(cpu); + if (rdp->nxtlist && !rdp->curlist) { + rdp->curlist = rdp->nxtlist; + rdp->curtail = rdp->nxttail; + rdp->nxtlist = NULL; + rdp->nxttail = &rdp->nxtlist; local_irq_enable(); /* * start the next batch of callbacks */ - do { - seq = read_seqcount_begin(&rcu_ctrlblk.lock); - /* determine batch number */ - RCU_batch(cpu) = rcu_ctrlblk.cur + 1; - next_pending = rcu_ctrlblk.next_pending; - } while (read_seqcount_retry(&rcu_ctrlblk.lock, seq)); - - if (!next_pending) { + + /* determine batch number */ + rdp->batch = rcp->cur + 1; + /* see the comment and corresponding wmb() in + * the rcu_start_batch() + */ + smp_rmb(); + + if (!rcp->next_pending) { /* and start it/schedule start if it's a new batch */ - spin_lock(&rcu_state.mutex); - rcu_start_batch(1); - spin_unlock(&rcu_state.mutex); + spin_lock(&rsp->lock); + rcu_start_batch(rcp, rsp, 1); + spin_unlock(&rsp->lock); } } else { local_irq_enable(); } - rcu_check_quiescent_state(); - if (rcu_list) - rcu_do_batch(rcu_list); + rcu_check_quiescent_state(rcp, rsp, rdp); + if (rdp->donelist) + rcu_do_batch(rdp); +} + +static void rcu_process_callbacks(unsigned long unused) +{ + __rcu_process_callbacks(&rcu_ctrlblk, &rcu_state, + &__get_cpu_var(rcu_data)); + __rcu_process_callbacks(&rcu_bh_ctrlblk, &rcu_bh_state, + &__get_cpu_var(rcu_bh_data)); } void rcu_check_callbacks(int cpu, int user) { if (user || (idle_cpu(cpu) && !in_softirq() && - hardirq_count() <= (1 << HARDIRQ_SHIFT))) - RCU_qsctr(cpu)++; - tasklet_schedule(&RCU_tasklet(cpu)); + hardirq_count() <= (1 << HARDIRQ_SHIFT))) { + rcu_qsctr_inc(cpu); + rcu_bh_qsctr_inc(cpu); + } else if (!in_softirq()) + rcu_bh_qsctr_inc(cpu); + tasklet_schedule(&per_cpu(rcu_tasklet, cpu)); +} + +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->donetail = &rdp->donelist; + rdp->quiescbatch = rcp->completed; + rdp->qs_pending = 0; + rdp->cpu = cpu; } static void __devinit rcu_online_cpu(int cpu) { - memset(&per_cpu(rcu_data, cpu), 0, sizeof(struct rcu_data)); - tasklet_init(&RCU_tasklet(cpu), rcu_process_callbacks, 0UL); - RCU_nxttail(cpu) = &RCU_nxtlist(cpu); - RCU_quiescbatch(cpu) = rcu_ctrlblk.completed; - RCU_qs_pending(cpu) = 0; + struct rcu_data *rdp = &per_cpu(rcu_data, cpu); + struct rcu_data *bh_rdp = &per_cpu(rcu_bh_data, cpu); + + rcu_init_percpu_data(cpu, &rcu_ctrlblk, rdp); + rcu_init_percpu_data(cpu, &rcu_bh_ctrlblk, bh_rdp); + tasklet_init(&per_cpu(rcu_tasklet, cpu), rcu_process_callbacks, 0UL); } static int __devinit rcu_cpu_notify(struct notifier_block *self, @@ -326,11 +402,9 @@ static int __devinit rcu_cpu_notify(struct notifier_block *self, case CPU_UP_PREPARE: rcu_online_cpu(cpu); break; -#ifdef CONFIG_HOTPLUG_CPU case CPU_DEAD: rcu_offline_cpu(cpu); break; -#endif default: break; } @@ -370,8 +444,13 @@ static void wakeme_after_rcu(struct rcu_head *head) } /** - * synchronize-kernel - wait until all the CPUs have gone - * through a "quiescent" state. It may sleep. + * synchronize_kernel - wait until a grace period has elapsed. + * + * Control will return to the caller some time after a full grace + * period has elapsed, in other words after all currently executing RCU + * read-side critical sections have completed. RCU read-side critical + * sections are delimited by rcu_read_lock() and rcu_read_unlock(), + * and may be nested. */ void synchronize_kernel(void) { @@ -385,6 +464,7 @@ void synchronize_kernel(void) wait_for_completion(&rcu.completion); } - +module_param(maxbatch, int, 0); EXPORT_SYMBOL(call_rcu); +EXPORT_SYMBOL(call_rcu_bh); EXPORT_SYMBOL(synchronize_kernel);