epoch: add non-preemptible "critical" variant
adds: - epoch_enter_critical() - can be called inside a different epoch, starts a section that will acquire any MTX_DEF mutexes or do anything that might sleep. - epoch_exit_critical() - corresponding exit call - epoch_wait_critical() - wait variant that is guaranteed that any threads in a section are running. - epoch_global_critical - an epoch_wait_critical safe epoch instance Requested by: markj Approved by: sbruno
This commit is contained in:
Matt Macy
parent
dedc82ae26
commit
5e68a3dfe3
@ -83,6 +83,12 @@ SYSCTL_COUNTER_U64(_kern_epoch_stats, OID_AUTO, ncontended, CTLFLAG_RW,
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static counter_u64_t switch_count;
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SYSCTL_COUNTER_U64(_kern_epoch_stats, OID_AUTO, switches, CTLFLAG_RW,
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&switch_count, "# of times a thread voluntarily context switched in epoch_wait");
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static counter_u64_t epoch_call_count;
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SYSCTL_COUNTER_U64(_kern_epoch_stats, OID_AUTO, epoch_calls, CTLFLAG_RW,
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&epoch_call_count, "# of times a callback was deferred");
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static counter_u64_t epoch_call_task_count;
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SYSCTL_COUNTER_U64(_kern_epoch_stats, OID_AUTO, epoch_call_tasks, CTLFLAG_RW,
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&epoch_call_task_count, "# of times a callback task was run");
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TAILQ_HEAD(threadlist, thread);
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@ -103,9 +109,8 @@ struct epoch_pcpu_state {
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struct epoch {
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struct ck_epoch e_epoch __aligned(EPOCH_ALIGN);
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struct epoch_pcpu_state *e_pcpu_dom[MAXMEMDOM] __aligned(EPOCH_ALIGN);
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counter_u64_t e_frees;
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uint64_t e_free_last;
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int e_idx;
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int e_flags;
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struct epoch_pcpu_state *e_pcpu[0];
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};
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@ -119,7 +124,7 @@ static __read_mostly int domoffsets[MAXMEMDOM];
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static __read_mostly int inited;
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static __read_mostly int epoch_count;
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__read_mostly epoch_t global_epoch;
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static __read_mostly epoch_t private_epoch;
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__read_mostly epoch_t global_epoch_critical;
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static void epoch_call_task(void *context __unused);
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@ -161,8 +166,8 @@ epoch_init(void *arg __unused)
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taskqgroup_attach_cpu(qgroup_softirq, DPCPU_ID_PTR(cpu, epoch_cb_task), NULL, cpu, -1, "epoch call task");
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}
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inited = 1;
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global_epoch = epoch_alloc();
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private_epoch = epoch_alloc();
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global_epoch = epoch_alloc(0);
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global_epoch_critical = epoch_alloc(EPOCH_CRITICAL);
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}
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SYSINIT(epoch, SI_SUB_TASKQ + 1, SI_ORDER_FIRST, epoch_init, NULL);
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@ -206,7 +211,7 @@ epoch_init_legacy(epoch_t epoch)
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}
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epoch_t
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epoch_alloc(void)
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epoch_alloc(int flags)
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{
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epoch_t epoch;
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@ -215,12 +220,12 @@ 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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epoch->e_frees = counter_u64_alloc(M_WAITOK);
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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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MPASS(epoch_count < MAX_EPOCHS-2);
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epoch->e_flags = flags;
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epoch->e_idx = epoch_count;
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allepochs[epoch_count++] = epoch;
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return (epoch);
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@ -240,11 +245,7 @@ epoch_free(epoch_t epoch)
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}
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#endif
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allepochs[epoch->e_idx] = NULL;
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epoch_wait(private_epoch);
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/*
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* Execute any lingering callbacks
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*/
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counter_u64_free(epoch->e_frees);
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epoch_wait_critical(global_epoch_critical);
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if (usedomains)
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for (domain = 0; domain < vm_ndomains; domain++)
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free_domain(epoch->e_pcpu_dom[domain], M_EPOCH);
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@ -289,14 +290,21 @@ epoch_enter_internal(epoch_t epoch, struct thread *td)
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}
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static void
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epoch_enter_private(ck_epoch_section_t *section)
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void
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epoch_enter_critical(epoch_t epoch)
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{
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struct epoch_pcpu_state *eps;
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ck_epoch_record_t *record;
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ck_epoch_section_t *section;
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struct thread *td;
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MPASS(curthread->td_critnest);
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eps = private_epoch->e_pcpu[curcpu];
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ck_epoch_begin(&eps->eps_record.er_record, section);
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section = NULL;
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td = curthread;
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critical_enter();
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if (__predict_true(td->td_epochnest++ == 0))
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section = (ck_epoch_section_t*)&td->td_epoch_section;
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record = &epoch->e_pcpu[curcpu]->eps_record.er_record;
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ck_epoch_begin(record, section);
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}
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void
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@ -321,14 +329,21 @@ epoch_exit_internal(epoch_t epoch, struct thread *td)
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critical_exit();
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}
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static void
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epoch_exit_private(ck_epoch_section_t *section)
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void
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epoch_exit_critical(epoch_t epoch)
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{
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struct epoch_pcpu_state *eps;
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ck_epoch_record_t *record;
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ck_epoch_section_t *section;
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struct thread *td;
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MPASS(curthread->td_critnest);
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eps = private_epoch->e_pcpu[curcpu];
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ck_epoch_end(&eps->eps_record.er_record, section);
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section = NULL;
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td = curthread;
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MPASS(td->td_critnest);
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if (__predict_true(td->td_epochnest-- == 1))
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section = (ck_epoch_section_t*)&td->td_epoch_section;
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record = &epoch->e_pcpu[curcpu]->eps_record.er_record;
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ck_epoch_end(record, section);
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critical_exit();
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}
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/*
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@ -517,6 +532,23 @@ epoch_wait(epoch_t epoch)
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("%d residual locks held", td->td_locks - locks));
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}
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static void
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epoch_block_handler_critical(struct ck_epoch *g __unused, ck_epoch_record_t *c __unused,
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void *arg __unused)
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{
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cpu_spinwait();
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}
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void
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epoch_wait_critical(epoch_t epoch)
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{
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MPASS(epoch->e_flags & EPOCH_CRITICAL);
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critical_enter();
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ck_epoch_synchronize_wait(&epoch->e_epoch, epoch_block_handler_critical, NULL);
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critical_exit();
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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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@ -530,8 +562,6 @@ epoch_call(epoch_t epoch, epoch_context_t ctx, void (*callback) (epoch_context_t
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if (__predict_false(epoch == NULL))
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goto boottime;
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counter_u64_add(epoch->e_frees, 1);
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critical_enter();
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*DPCPU_PTR(epoch_cb_count) += 1;
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eps = epoch->e_pcpu[curcpu];
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@ -542,20 +572,18 @@ epoch_call(epoch_t epoch, epoch_context_t ctx, void (*callback) (epoch_context_t
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callback(ctx);
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}
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static void
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epoch_call_task(void *arg __unused)
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{
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ck_stack_entry_t *cursor, *head, *next;
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ck_epoch_record_t *record;
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ck_epoch_section_t section;
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epoch_t epoch;
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ck_stack_t cb_stack;
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int i, npending, total;
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ck_stack_init(&cb_stack);
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critical_enter();
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epoch_enter_private(§ion);
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epoch_enter_critical(global_epoch_critical);
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for (total = i = 0; i < epoch_count; i++) {
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if (__predict_false((epoch = allepochs[i]) == NULL))
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continue;
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@ -565,10 +593,13 @@ epoch_call_task(void *arg __unused)
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ck_epoch_poll_deferred(record, &cb_stack);
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total += npending - record->n_pending;
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}
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epoch_exit_private(§ion);
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epoch_exit_critical(global_epoch_critical);
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*DPCPU_PTR(epoch_cb_count) -= total;
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critical_exit();
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counter_u64_add(epoch_call_count, total);
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counter_u64_add(epoch_call_task_count, 1);
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head = ck_stack_batch_pop_npsc(&cb_stack);
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for (cursor = head; cursor != NULL; cursor = next) {
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struct ck_epoch_entry *entry =
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@ -903,7 +903,7 @@ if_attachdomain(void *dummy)
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{
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struct ifnet *ifp;
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net_epoch = epoch_alloc();
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net_epoch = epoch_alloc(0);
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TAILQ_FOREACH(ifp, &V_ifnet, if_link)
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if_attachdomain1(ifp);
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}
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@ -35,7 +35,10 @@
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struct epoch;
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typedef struct epoch *epoch_t;
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#define EPOCH_CRITICAL 0x1
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extern epoch_t global_epoch;
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extern epoch_t global_epoch_critical;
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DPCPU_DECLARE(int, epoch_cb_count);
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DPCPU_DECLARE(struct grouptask, epoch_cb_task);
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@ -45,11 +48,14 @@ struct epoch_context {
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typedef struct epoch_context *epoch_context_t;
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epoch_t epoch_alloc(void);
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epoch_t epoch_alloc(int flags);
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void epoch_free(epoch_t epoch);
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void epoch_enter_critical(epoch_t epoch);
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void epoch_enter_internal(epoch_t epoch, struct thread *td);
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void epoch_exit_critical(epoch_t epoch);
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void epoch_exit_internal(epoch_t epoch, struct thread *td);
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void epoch_wait(epoch_t epoch);
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void epoch_wait_critical(epoch_t epoch);
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void epoch_call(epoch_t epoch, epoch_context_t ctx, void (*callback) (epoch_context_t));
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int in_epoch(void);
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@ -29,6 +29,7 @@ __FBSDID("$FreeBSD$");
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#include <sys/param.h>
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#include <sys/types.h>
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#include <sys/proc.h>
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#include <sys/counter.h>
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#include <sys/epoch.h>
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#include <sys/gtaskqueue.h>
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@ -138,7 +139,7 @@ test_modinit(void)
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int i, error, pri_range, pri_off;
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pri_range = PRI_MIN_TIMESHARE - PRI_MIN_REALTIME;
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test_epoch = epoch_alloc();
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test_epoch = epoch_alloc(0);
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for (i = 0; i < mp_ncpus*2; i++) {
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etilist[i].threadid = i;
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error = kthread_add(testloop, &etilist[i], NULL, &testthreads[i],
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