epoch(9): fix priority handling, make callback lists pcpu, and other fixes
- Lend priority to preempted threads in epoch_wait to handle the case in which we've had priority lent to us. Previously we borrowed the priority of the lowest priority preempted thread. (pointed out by mjg@) - Don't attempt allocate memory per-domain on powerpc, we don't currently handle empty sockets (as is the case on jhibbits Talos' board). - Handle deferred callbacks as pcpu lists and poll the lists periodically. Currently the interval is 1/hz. - Drop the thread lock when adaptive spinning. Holding the lock starves other threads and can even lead to lockups. - Keep a generation count pcpu so that we don't keep spining if a thread has left and re-entered an epoch section. - Actually removed the callback from the callback list so that we don't double free. Sigh ... Approved by: sbruno@
This commit is contained in:
Matt Macy
parent
ef7f29d8e6
commit
b2cb28963b
@ -54,9 +54,19 @@ MALLOC_DEFINE(M_EPOCH, "epoch", "epoch based reclamation");
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/* arbitrary --- needs benchmarking */
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#define MAX_ADAPTIVE_SPIN 5000
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#define EPOCH_EXITING 0x1
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#ifdef __amd64__
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#define EPOCH_ALIGN CACHE_LINE_SIZE*2
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#else
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#define EPOCH_ALIGN CACHE_LINE_SIZE
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#endif
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SYSCTL_NODE(_kern, OID_AUTO, epoch, CTLFLAG_RW, 0, "epoch information");
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SYSCTL_NODE(_kern_epoch, OID_AUTO, stats, CTLFLAG_RW, 0, "epoch stats");
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static int poll_intvl;
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SYSCTL_INT(_kern_epoch, OID_AUTO, poll_intvl, CTLFLAG_RWTUN,
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&poll_intvl, 0, "# of ticks to wait between garbage collecting deferred frees");
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/* Stats. */
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static counter_u64_t block_count;
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SYSCTL_COUNTER_U64(_kern_epoch_stats, OID_AUTO, nblocked, CTLFLAG_RW,
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@ -81,20 +91,23 @@ TAILQ_HEAD(threadlist, thread);
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typedef struct epoch_record {
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ck_epoch_record_t er_record;
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volatile struct threadlist er_tdlist;
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volatile uint32_t er_gen;
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uint32_t er_cpuid;
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} *epoch_record_t;
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struct epoch_pcpu_state {
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struct epoch_record eps_record;
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volatile int eps_waiters;
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} __aligned(CACHE_LINE_SIZE);
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STAILQ_HEAD(, epoch_cb) eps_cblist;
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} __aligned(EPOCH_ALIGN);
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struct epoch {
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struct ck_epoch e_epoch;
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struct mtx e_lock;
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struct ck_epoch e_epoch __aligned(EPOCH_ALIGN);
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struct grouptask e_gtask;
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STAILQ_HEAD(, epoch_cb) e_cblist;
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struct epoch_pcpu_state *e_pcpu_dom[MAXMEMDOM];
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struct callout e_timer;
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struct mtx e_lock;
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int e_flags;
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/* make sure that immutable data doesn't overlap with the gtask, callout, and mutex*/
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struct epoch_pcpu_state *e_pcpu_dom[MAXMEMDOM] __aligned(EPOCH_ALIGN);
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struct epoch_pcpu_state *e_pcpu[0];
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};
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@ -103,13 +116,26 @@ static __read_mostly int domoffsets[MAXMEMDOM];
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static __read_mostly int inited;
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static void epoch_call_task(void *context);
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static bool usedomains = true;
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#if defined(__powerpc64__) || defined(__powerpc__)
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static bool usedomains = false;
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#else
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static bool usedomains = true;
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#endif
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static void
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epoch_init(void *arg __unused)
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{
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int domain, count;
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if (poll_intvl == 0)
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poll_intvl = hz;
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block_count = counter_u64_alloc(M_WAITOK);
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migrate_count = counter_u64_alloc(M_WAITOK);
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turnstile_count = counter_u64_alloc(M_WAITOK);
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switch_count = counter_u64_alloc(M_WAITOK);
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if (usedomains == false)
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return;
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count = domain = 0;
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domoffsets[0] = 0;
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for (domain = 0; domain < vm_ndomains; domain++) {
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@ -127,10 +153,6 @@ epoch_init(void *arg __unused)
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}
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}
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block_count = counter_u64_alloc(M_WAITOK);
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migrate_count = counter_u64_alloc(M_WAITOK);
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turnstile_count = counter_u64_alloc(M_WAITOK);
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switch_count = counter_u64_alloc(M_WAITOK);
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inited = 1;
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}
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SYSINIT(epoch, SI_SUB_CPU + 1, SI_ORDER_FIRST, epoch_init, NULL);
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@ -170,10 +192,22 @@ epoch_init_legacy(epoch_t epoch)
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er = &eps->eps_record;
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ck_epoch_register(&epoch->e_epoch, &er->er_record, NULL);
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TAILQ_INIT((struct threadlist *)(uintptr_t)&er->er_tdlist);
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STAILQ_INIT(&eps->eps_cblist);
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er->er_cpuid = i;
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}
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}
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static void
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epoch_callout(void *arg)
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{
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epoch_t epoch;
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epoch = arg;
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GROUPTASK_ENQUEUE(&epoch->e_gtask);
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if ((epoch->e_flags & EPOCH_EXITING) == 0)
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callout_reset(&epoch->e_timer, poll_intvl, epoch_callout, epoch);
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}
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epoch_t
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epoch_alloc(void)
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{
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@ -184,13 +218,14 @@ epoch_alloc(void)
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epoch = malloc(sizeof(struct epoch) + mp_ncpus*sizeof(void*),
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M_EPOCH, M_ZERO|M_WAITOK);
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ck_epoch_init(&epoch->e_epoch);
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mtx_init(&epoch->e_lock, "epoch cblist", NULL, MTX_DEF);
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STAILQ_INIT(&epoch->e_cblist);
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mtx_init(&epoch->e_lock, "epoch callout", NULL, MTX_DEF);
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callout_init_mtx(&epoch->e_timer, &epoch->e_lock, 0);
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taskqgroup_config_gtask_init(epoch, &epoch->e_gtask, epoch_call_task, "epoch call task");
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if (usedomains)
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epoch_init_numa(epoch);
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else
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epoch_init_legacy(epoch);
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callout_reset(&epoch->e_timer, poll_intvl, epoch_callout, epoch);
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return (epoch);
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}
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@ -207,6 +242,15 @@ epoch_free(epoch_t epoch)
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MPASS(TAILQ_EMPTY(&eps->eps_record.er_tdlist));
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}
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#endif
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mtx_lock(&epoch->e_lock);
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epoch->e_flags |= EPOCH_EXITING;
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mtx_unlock(&epoch->e_lock);
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/*
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* Execute any lingering callbacks
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*/
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GROUPTASK_ENQUEUE(&epoch->e_gtask);
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gtaskqueue_drain(epoch->e_gtask.gt_taskqueue, &epoch->e_gtask.gt_task);
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callout_drain(&epoch->e_timer);
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mtx_destroy(&epoch->e_lock);
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taskqgroup_config_gtask_deinit(&epoch->e_gtask);
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if (usedomains)
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@ -282,6 +326,7 @@ epoch_exit(epoch_t epoch)
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td->td_epochnest--;
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if (td->td_epochnest == 0)
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TAILQ_REMOVE(&eps->eps_record.er_tdlist, td, td_epochq);
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eps->eps_record.er_gen++;
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critical_exit();
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}
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@ -311,8 +356,7 @@ epoch_block_handler(struct ck_epoch *global __unused, ck_epoch_record_t *cr,
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struct thread *td, *tdwait, *owner;
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struct turnstile *ts;
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struct lock_object *lock;
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u_char prio;
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int spincount;
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int spincount, gen;
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eps = arg;
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record = __containerof(cr, struct epoch_record, er_record);
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@ -327,10 +371,14 @@ epoch_block_handler(struct ck_epoch *global __unused, ck_epoch_record_t *cr,
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*/
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if ((tdwait = TAILQ_FIRST(&record->er_tdlist)) != NULL &&
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TD_IS_RUNNING(tdwait)) {
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while (tdwait == TAILQ_FIRST(&record->er_tdlist) &&
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TD_IS_RUNNING(tdwait) && spincount++ < MAX_ADAPTIVE_SPIN) {
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gen = record->er_gen;
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thread_unlock(td);
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do {
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cpu_spinwait();
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}
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} while (tdwait == TAILQ_FIRST(&record->er_tdlist) &&
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gen == record->er_gen && TD_IS_RUNNING(tdwait) &&
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spincount++ < MAX_ADAPTIVE_SPIN);
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thread_lock(td);
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return;
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}
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@ -360,10 +408,17 @@ epoch_block_handler(struct ck_epoch *global __unused, ck_epoch_record_t *cr,
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* priority thread (highest prio value) and drop our priority
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* to match to allow it to run.
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*/
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prio = 0;
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TAILQ_FOREACH(tdwait, &record->er_tdlist, td_epochq) {
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if (td->td_priority > prio)
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prio = td->td_priority;
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/*
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* Propagate our priority to any other waiters to prevent us
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* from starving them. They will have their original priority
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* restore on exit from epoch_wait().
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*/
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if (!TD_IS_INHIBITED(tdwait) && tdwait->td_priority > td->td_priority) {
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thread_lock(tdwait);
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sched_prio(tdwait, td->td_priority);
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thread_unlock(tdwait);
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}
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if (TD_IS_INHIBITED(tdwait) && TD_ON_LOCK(tdwait) &&
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((ts = tdwait->td_blocked) != NULL)) {
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/*
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@ -401,12 +456,9 @@ epoch_block_handler(struct ck_epoch *global __unused, ck_epoch_record_t *cr,
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}
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/*
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* We didn't find any threads actually blocked on a lock
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* we have nothing to do except set our priority to match
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* that of the lowest value on the queue and context switch
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* away.
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* so we have nothing to do except context switch away.
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*/
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counter_u64_add(switch_count, 1);
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sched_prio(td, prio);
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mi_switch(SW_VOL | SWT_RELINQUISH, NULL);
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/*
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@ -464,41 +516,58 @@ epoch_wait(epoch_t epoch)
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/* restore thread priority */
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sched_prio(td, old_prio);
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thread_unlock(td);
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KASSERT(td->td_locks == 0,
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("%d locks held", td->td_locks));
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PICKUP_GIANT();
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}
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void
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epoch_call(epoch_t epoch, epoch_context_t ctx, void (*callback) (epoch_context_t))
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{
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struct epoch_pcpu_state *eps;
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epoch_cb_t cb;
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cb = (void *)ctx;
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MPASS(cb->ec_callback == NULL);
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MPASS(cb->ec_link.stqe_next == NULL);
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MPASS(epoch);
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MPASS(callback);
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cb->ec_callback = callback;
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mtx_lock(&epoch->e_lock);
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STAILQ_INSERT_TAIL(&epoch->e_cblist, cb, ec_link);
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GROUPTASK_ENQUEUE(&epoch->e_gtask);
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mtx_unlock(&epoch->e_lock);
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critical_enter();
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eps = epoch->e_pcpu[curcpu];
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STAILQ_INSERT_HEAD(&eps->eps_cblist, cb, ec_link);
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critical_exit();
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}
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static void
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epoch_call_task(void *context)
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{
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struct epoch_pcpu_state *eps;
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epoch_t epoch;
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epoch_cb_t cb;
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struct thread *td;
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int cpu;
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STAILQ_HEAD(, epoch_cb) tmp_head;
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epoch = context;
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STAILQ_INIT(&tmp_head);
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mtx_lock(&epoch->e_lock);
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STAILQ_CONCAT(&tmp_head, &epoch->e_cblist);
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mtx_unlock(&epoch->e_lock);
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td = curthread;
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thread_lock(td);
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CPU_FOREACH(cpu) {
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sched_bind(td, cpu);
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eps = epoch->e_pcpu[cpu];
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if (!STAILQ_EMPTY(&eps->eps_cblist))
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STAILQ_CONCAT(&tmp_head, &eps->eps_cblist);
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}
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sched_unbind(td);
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thread_unlock(td);
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epoch_wait(epoch);
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while ((cb = STAILQ_FIRST(&tmp_head)) != NULL)
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while ((cb = STAILQ_FIRST(&tmp_head)) != NULL) {
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STAILQ_REMOVE_HEAD(&tmp_head, ec_link);
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cb->ec_callback((void*)cb);
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}
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}
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int
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