freebsd-dev/sys/kern/subr_epoch.c
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1020 lines
26 KiB
C

/*-
* SPDX-License-Identifier: BSD-2-Clause
*
* Copyright (c) 2018, Matthew Macy <mmacy@freebsd.org>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
*/
#include <sys/cdefs.h>
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/counter.h>
#include <sys/epoch.h>
#include <sys/gtaskqueue.h>
#include <sys/kernel.h>
#include <sys/limits.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/pcpu.h>
#include <sys/proc.h>
#include <sys/sched.h>
#include <sys/sx.h>
#include <sys/smp.h>
#include <sys/sysctl.h>
#include <sys/turnstile.h>
#ifdef EPOCH_TRACE
#include <machine/stdarg.h>
#include <sys/stack.h>
#include <sys/tree.h>
#endif
#include <vm/vm.h>
#include <vm/vm_extern.h>
#include <vm/vm_kern.h>
#include <vm/uma.h>
#include <machine/stack.h>
#include <ck_epoch.h>
#ifdef __amd64__
#define EPOCH_ALIGN CACHE_LINE_SIZE*2
#else
#define EPOCH_ALIGN CACHE_LINE_SIZE
#endif
TAILQ_HEAD (epoch_tdlist, epoch_tracker);
typedef struct epoch_record {
ck_epoch_record_t er_record;
struct epoch_context er_drain_ctx;
struct epoch *er_parent;
volatile struct epoch_tdlist er_tdlist;
volatile uint32_t er_gen;
uint32_t er_cpuid;
#ifdef INVARIANTS
/* Used to verify record ownership for non-preemptible epochs. */
struct thread *er_td;
#endif
} __aligned(EPOCH_ALIGN) *epoch_record_t;
struct epoch {
struct ck_epoch e_epoch __aligned(EPOCH_ALIGN);
epoch_record_t e_pcpu_record;
int e_in_use;
int e_flags;
struct sx e_drain_sx;
struct mtx e_drain_mtx;
volatile int e_drain_count;
const char *e_name;
};
/* arbitrary --- needs benchmarking */
#define MAX_ADAPTIVE_SPIN 100
#define MAX_EPOCHS 64
CTASSERT(sizeof(ck_epoch_entry_t) == sizeof(struct epoch_context));
SYSCTL_NODE(_kern, OID_AUTO, epoch, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
"epoch information");
SYSCTL_NODE(_kern_epoch, OID_AUTO, stats, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
"epoch stats");
/* Stats. */
static counter_u64_t block_count;
SYSCTL_COUNTER_U64(_kern_epoch_stats, OID_AUTO, nblocked, CTLFLAG_RW,
&block_count, "# of times a thread was in an epoch when epoch_wait was called");
static counter_u64_t migrate_count;
SYSCTL_COUNTER_U64(_kern_epoch_stats, OID_AUTO, migrations, CTLFLAG_RW,
&migrate_count, "# of times thread was migrated to another CPU in epoch_wait");
static counter_u64_t turnstile_count;
SYSCTL_COUNTER_U64(_kern_epoch_stats, OID_AUTO, ncontended, CTLFLAG_RW,
&turnstile_count, "# of times a thread was blocked on a lock in an epoch during an epoch_wait");
static counter_u64_t switch_count;
SYSCTL_COUNTER_U64(_kern_epoch_stats, OID_AUTO, switches, CTLFLAG_RW,
&switch_count, "# of times a thread voluntarily context switched in epoch_wait");
static counter_u64_t epoch_call_count;
SYSCTL_COUNTER_U64(_kern_epoch_stats, OID_AUTO, epoch_calls, CTLFLAG_RW,
&epoch_call_count, "# of times a callback was deferred");
static counter_u64_t epoch_call_task_count;
SYSCTL_COUNTER_U64(_kern_epoch_stats, OID_AUTO, epoch_call_tasks, CTLFLAG_RW,
&epoch_call_task_count, "# of times a callback task was run");
TAILQ_HEAD (threadlist, thread);
CK_STACK_CONTAINER(struct ck_epoch_entry, stack_entry,
ck_epoch_entry_container)
static struct epoch epoch_array[MAX_EPOCHS];
DPCPU_DEFINE(struct grouptask, epoch_cb_task);
DPCPU_DEFINE(int, epoch_cb_count);
static __read_mostly int inited;
__read_mostly epoch_t global_epoch;
__read_mostly epoch_t global_epoch_preempt;
static void epoch_call_task(void *context __unused);
static uma_zone_t pcpu_zone_record;
static struct sx epoch_sx;
#define EPOCH_LOCK() sx_xlock(&epoch_sx)
#define EPOCH_UNLOCK() sx_xunlock(&epoch_sx)
static epoch_record_t
epoch_currecord(epoch_t epoch)
{
return (zpcpu_get(epoch->e_pcpu_record));
}
#ifdef EPOCH_TRACE
struct stackentry {
RB_ENTRY(stackentry) se_node;
struct stack se_stack;
};
static int
stackentry_compare(struct stackentry *a, struct stackentry *b)
{
if (a->se_stack.depth > b->se_stack.depth)
return (1);
if (a->se_stack.depth < b->se_stack.depth)
return (-1);
for (int i = 0; i < a->se_stack.depth; i++) {
if (a->se_stack.pcs[i] > b->se_stack.pcs[i])
return (1);
if (a->se_stack.pcs[i] < b->se_stack.pcs[i])
return (-1);
}
return (0);
}
RB_HEAD(stacktree, stackentry) epoch_stacks = RB_INITIALIZER(&epoch_stacks);
RB_GENERATE_STATIC(stacktree, stackentry, se_node, stackentry_compare);
static struct mtx epoch_stacks_lock;
MTX_SYSINIT(epochstacks, &epoch_stacks_lock, "epoch_stacks", MTX_DEF);
static bool epoch_trace_stack_print = true;
SYSCTL_BOOL(_kern_epoch, OID_AUTO, trace_stack_print, CTLFLAG_RWTUN,
&epoch_trace_stack_print, 0, "Print stack traces on epoch reports");
static void epoch_trace_report(const char *fmt, ...) __printflike(1, 2);
static inline void
epoch_trace_report(const char *fmt, ...)
{
va_list ap;
struct stackentry se, *new;
stack_save(&se.se_stack);
/* Tree is never reduced - go lockless. */
if (RB_FIND(stacktree, &epoch_stacks, &se) != NULL)
return;
new = malloc(sizeof(*new), M_STACK, M_NOWAIT);
if (new != NULL) {
bcopy(&se.se_stack, &new->se_stack, sizeof(struct stack));
mtx_lock(&epoch_stacks_lock);
new = RB_INSERT(stacktree, &epoch_stacks, new);
mtx_unlock(&epoch_stacks_lock);
if (new != NULL)
free(new, M_STACK);
}
va_start(ap, fmt);
(void)vprintf(fmt, ap);
va_end(ap);
if (epoch_trace_stack_print)
stack_print_ddb(&se.se_stack);
}
static inline void
epoch_trace_enter(struct thread *td, epoch_t epoch, epoch_tracker_t et,
const char *file, int line)
{
epoch_tracker_t iet;
SLIST_FOREACH(iet, &td->td_epochs, et_tlink) {
if (iet->et_epoch != epoch)
continue;
epoch_trace_report("Recursively entering epoch %s "
"at %s:%d, previously entered at %s:%d\n",
epoch->e_name, file, line,
iet->et_file, iet->et_line);
}
et->et_epoch = epoch;
et->et_file = file;
et->et_line = line;
et->et_flags = 0;
SLIST_INSERT_HEAD(&td->td_epochs, et, et_tlink);
}
static inline void
epoch_trace_exit(struct thread *td, epoch_t epoch, epoch_tracker_t et,
const char *file, int line)
{
if (SLIST_FIRST(&td->td_epochs) != et) {
epoch_trace_report("Exiting epoch %s in a not nested order "
"at %s:%d. Most recently entered %s at %s:%d\n",
epoch->e_name,
file, line,
SLIST_FIRST(&td->td_epochs)->et_epoch->e_name,
SLIST_FIRST(&td->td_epochs)->et_file,
SLIST_FIRST(&td->td_epochs)->et_line);
/* This will panic if et is not anywhere on td_epochs. */
SLIST_REMOVE(&td->td_epochs, et, epoch_tracker, et_tlink);
} else
SLIST_REMOVE_HEAD(&td->td_epochs, et_tlink);
if (et->et_flags & ET_REPORT_EXIT)
printf("Td %p exiting epoch %s at %s:%d\n", td, epoch->e_name,
file, line);
}
/* Used by assertions that check thread state before going to sleep. */
void
epoch_trace_list(struct thread *td)
{
epoch_tracker_t iet;
SLIST_FOREACH(iet, &td->td_epochs, et_tlink)
printf("Epoch %s entered at %s:%d\n", iet->et_epoch->e_name,
iet->et_file, iet->et_line);
}
void
epoch_where_report(epoch_t epoch)
{
epoch_record_t er;
struct epoch_tracker *tdwait;
MPASS(epoch != NULL);
MPASS((epoch->e_flags & EPOCH_PREEMPT) != 0);
MPASS(!THREAD_CAN_SLEEP());
critical_enter();
er = epoch_currecord(epoch);
TAILQ_FOREACH(tdwait, &er->er_tdlist, et_link)
if (tdwait->et_td == curthread)
break;
critical_exit();
if (tdwait != NULL) {
tdwait->et_flags |= ET_REPORT_EXIT;
printf("Td %p entered epoch %s at %s:%d\n", curthread,
epoch->e_name, tdwait->et_file, tdwait->et_line);
}
}
#endif /* EPOCH_TRACE */
static void
epoch_init(void *arg __unused)
{
int cpu;
block_count = counter_u64_alloc(M_WAITOK);
migrate_count = counter_u64_alloc(M_WAITOK);
turnstile_count = counter_u64_alloc(M_WAITOK);
switch_count = counter_u64_alloc(M_WAITOK);
epoch_call_count = counter_u64_alloc(M_WAITOK);
epoch_call_task_count = counter_u64_alloc(M_WAITOK);
pcpu_zone_record = uma_zcreate("epoch_record pcpu",
sizeof(struct epoch_record), NULL, NULL, NULL, NULL,
UMA_ALIGN_PTR, UMA_ZONE_PCPU);
CPU_FOREACH(cpu) {
GROUPTASK_INIT(DPCPU_ID_PTR(cpu, epoch_cb_task), 0,
epoch_call_task, NULL);
taskqgroup_attach_cpu(qgroup_softirq,
DPCPU_ID_PTR(cpu, epoch_cb_task), NULL, cpu, NULL, NULL,
"epoch call task");
}
#ifdef EPOCH_TRACE
SLIST_INIT(&thread0.td_epochs);
#endif
sx_init(&epoch_sx, "epoch-sx");
inited = 1;
global_epoch = epoch_alloc("Global", 0);
global_epoch_preempt = epoch_alloc("Global preemptible", EPOCH_PREEMPT);
}
SYSINIT(epoch, SI_SUB_EPOCH, SI_ORDER_FIRST, epoch_init, NULL);
#if !defined(EARLY_AP_STARTUP)
static void
epoch_init_smp(void *dummy __unused)
{
inited = 2;
}
SYSINIT(epoch_smp, SI_SUB_SMP + 1, SI_ORDER_FIRST, epoch_init_smp, NULL);
#endif
static void
epoch_ctor(epoch_t epoch)
{
epoch_record_t er;
int cpu;
epoch->e_pcpu_record = uma_zalloc_pcpu(pcpu_zone_record, M_WAITOK);
CPU_FOREACH(cpu) {
er = zpcpu_get_cpu(epoch->e_pcpu_record, cpu);
bzero(er, sizeof(*er));
ck_epoch_register(&epoch->e_epoch, &er->er_record, NULL);
TAILQ_INIT((struct threadlist *)(uintptr_t)&er->er_tdlist);
er->er_cpuid = cpu;
er->er_parent = epoch;
}
}
static void
epoch_adjust_prio(struct thread *td, u_char prio)
{
thread_lock(td);
sched_prio(td, prio);
thread_unlock(td);
}
epoch_t
epoch_alloc(const char *name, int flags)
{
epoch_t epoch;
int i;
MPASS(name != NULL);
if (__predict_false(!inited))
panic("%s called too early in boot", __func__);
EPOCH_LOCK();
/*
* Find a free index in the epoch array. If no free index is
* found, try to use the index after the last one.
*/
for (i = 0;; i++) {
/*
* If too many epochs are currently allocated,
* return NULL.
*/
if (i == MAX_EPOCHS) {
epoch = NULL;
goto done;
}
if (epoch_array[i].e_in_use == 0)
break;
}
epoch = epoch_array + i;
ck_epoch_init(&epoch->e_epoch);
epoch_ctor(epoch);
epoch->e_flags = flags;
epoch->e_name = name;
sx_init(&epoch->e_drain_sx, "epoch-drain-sx");
mtx_init(&epoch->e_drain_mtx, "epoch-drain-mtx", NULL, MTX_DEF);
/*
* Set e_in_use last, because when this field is set the
* epoch_call_task() function will start scanning this epoch
* structure.
*/
atomic_store_rel_int(&epoch->e_in_use, 1);
done:
EPOCH_UNLOCK();
return (epoch);
}
void
epoch_free(epoch_t epoch)
{
#ifdef INVARIANTS
int cpu;
#endif
EPOCH_LOCK();
MPASS(epoch->e_in_use != 0);
epoch_drain_callbacks(epoch);
atomic_store_rel_int(&epoch->e_in_use, 0);
/*
* Make sure the epoch_call_task() function see e_in_use equal
* to zero, by calling epoch_wait() on the global_epoch:
*/
epoch_wait(global_epoch);
#ifdef INVARIANTS
CPU_FOREACH(cpu) {
epoch_record_t er;
er = zpcpu_get_cpu(epoch->e_pcpu_record, cpu);
/*
* Sanity check: none of the records should be in use anymore.
* We drained callbacks above and freeing the pcpu records is
* imminent.
*/
MPASS(er->er_td == NULL);
MPASS(TAILQ_EMPTY(&er->er_tdlist));
}
#endif
uma_zfree_pcpu(pcpu_zone_record, epoch->e_pcpu_record);
mtx_destroy(&epoch->e_drain_mtx);
sx_destroy(&epoch->e_drain_sx);
memset(epoch, 0, sizeof(*epoch));
EPOCH_UNLOCK();
}
#define INIT_CHECK(epoch) \
do { \
if (__predict_false((epoch) == NULL)) \
return; \
} while (0)
void
_epoch_enter_preempt(epoch_t epoch, epoch_tracker_t et EPOCH_FILE_LINE)
{
struct epoch_record *er;
struct thread *td;
MPASS(cold || epoch != NULL);
td = curthread;
MPASS(kstack_contains(td, (vm_offset_t)et, sizeof(*et)));
INIT_CHECK(epoch);
MPASS(epoch->e_flags & EPOCH_PREEMPT);
#ifdef EPOCH_TRACE
epoch_trace_enter(td, epoch, et, file, line);
#endif
et->et_td = td;
THREAD_NO_SLEEPING();
critical_enter();
sched_pin();
et->et_old_priority = td->td_priority;
er = epoch_currecord(epoch);
/* Record-level tracking is reserved for non-preemptible epochs. */
MPASS(er->er_td == NULL);
TAILQ_INSERT_TAIL(&er->er_tdlist, et, et_link);
ck_epoch_begin(&er->er_record, &et->et_section);
critical_exit();
}
void
epoch_enter(epoch_t epoch)
{
epoch_record_t er;
MPASS(cold || epoch != NULL);
INIT_CHECK(epoch);
critical_enter();
er = epoch_currecord(epoch);
#ifdef INVARIANTS
if (er->er_record.active == 0) {
MPASS(er->er_td == NULL);
er->er_td = curthread;
} else {
/* We've recursed, just make sure our accounting isn't wrong. */
MPASS(er->er_td == curthread);
}
#endif
ck_epoch_begin(&er->er_record, NULL);
}
void
_epoch_exit_preempt(epoch_t epoch, epoch_tracker_t et EPOCH_FILE_LINE)
{
struct epoch_record *er;
struct thread *td;
INIT_CHECK(epoch);
td = curthread;
critical_enter();
sched_unpin();
THREAD_SLEEPING_OK();
er = epoch_currecord(epoch);
MPASS(epoch->e_flags & EPOCH_PREEMPT);
MPASS(et != NULL);
MPASS(et->et_td == td);
#ifdef INVARIANTS
et->et_td = (void*)0xDEADBEEF;
/* Record-level tracking is reserved for non-preemptible epochs. */
MPASS(er->er_td == NULL);
#endif
ck_epoch_end(&er->er_record, &et->et_section);
TAILQ_REMOVE(&er->er_tdlist, et, et_link);
er->er_gen++;
if (__predict_false(et->et_old_priority != td->td_priority))
epoch_adjust_prio(td, et->et_old_priority);
critical_exit();
#ifdef EPOCH_TRACE
epoch_trace_exit(td, epoch, et, file, line);
#endif
}
void
epoch_exit(epoch_t epoch)
{
epoch_record_t er;
INIT_CHECK(epoch);
er = epoch_currecord(epoch);
ck_epoch_end(&er->er_record, NULL);
#ifdef INVARIANTS
MPASS(er->er_td == curthread);
if (er->er_record.active == 0)
er->er_td = NULL;
#endif
critical_exit();
}
/*
* epoch_block_handler_preempt() is a callback from the CK code when another
* thread is currently in an epoch section.
*/
static void
epoch_block_handler_preempt(struct ck_epoch *global __unused,
ck_epoch_record_t *cr, void *arg __unused)
{
epoch_record_t record;
struct thread *td, *owner, *curwaittd;
struct epoch_tracker *tdwait;
struct turnstile *ts;
struct lock_object *lock;
int spincount, gen;
int locksheld __unused;
record = __containerof(cr, struct epoch_record, er_record);
td = curthread;
locksheld = td->td_locks;
spincount = 0;
counter_u64_add(block_count, 1);
/*
* We lost a race and there's no longer any threads
* on the CPU in an epoch section.
*/
if (TAILQ_EMPTY(&record->er_tdlist))
return;
if (record->er_cpuid != curcpu) {
/*
* If the head of the list is running, we can wait for it
* to remove itself from the list and thus save us the
* overhead of a migration
*/
gen = record->er_gen;
thread_unlock(td);
/*
* We can't actually check if the waiting thread is running
* so we simply poll for it to exit before giving up and
* migrating.
*/
do {
cpu_spinwait();
} while (!TAILQ_EMPTY(&record->er_tdlist) &&
gen == record->er_gen &&
spincount++ < MAX_ADAPTIVE_SPIN);
thread_lock(td);
/*
* If the generation has changed we can poll again
* otherwise we need to migrate.
*/
if (gen != record->er_gen)
return;
/*
* Being on the same CPU as that of the record on which
* we need to wait allows us access to the thread
* list associated with that CPU. We can then examine the
* oldest thread in the queue and wait on its turnstile
* until it resumes and so on until a grace period
* elapses.
*
*/
counter_u64_add(migrate_count, 1);
sched_bind(td, record->er_cpuid);
/*
* At this point we need to return to the ck code
* to scan to see if a grace period has elapsed.
* We can't move on to check the thread list, because
* in the meantime new threads may have arrived that
* in fact belong to a different epoch.
*/
return;
}
/*
* Try to find a thread in an epoch section on this CPU
* waiting on a turnstile. Otherwise find the lowest
* priority thread (highest prio value) and drop our priority
* to match to allow it to run.
*/
TAILQ_FOREACH(tdwait, &record->er_tdlist, et_link) {
/*
* Propagate our priority to any other waiters to prevent us
* from starving them. They will have their original priority
* restore on exit from epoch_wait().
*/
curwaittd = tdwait->et_td;
if (!TD_IS_INHIBITED(curwaittd) && curwaittd->td_priority > td->td_priority) {
critical_enter();
thread_unlock(td);
thread_lock(curwaittd);
sched_prio(curwaittd, td->td_priority);
thread_unlock(curwaittd);
thread_lock(td);
critical_exit();
}
if (TD_IS_INHIBITED(curwaittd) && TD_ON_LOCK(curwaittd) &&
((ts = curwaittd->td_blocked) != NULL)) {
/*
* We unlock td to allow turnstile_wait to reacquire
* the thread lock. Before unlocking it we enter a
* critical section to prevent preemption after we
* reenable interrupts by dropping the thread lock in
* order to prevent curwaittd from getting to run.
*/
critical_enter();
thread_unlock(td);
if (turnstile_lock(ts, &lock, &owner)) {
if (ts == curwaittd->td_blocked) {
MPASS(TD_IS_INHIBITED(curwaittd) &&
TD_ON_LOCK(curwaittd));
critical_exit();
turnstile_wait(ts, owner,
curwaittd->td_tsqueue);
counter_u64_add(turnstile_count, 1);
thread_lock(td);
return;
}
turnstile_unlock(ts, lock);
}
thread_lock(td);
critical_exit();
KASSERT(td->td_locks == locksheld,
("%d extra locks held", td->td_locks - locksheld));
}
}
/*
* We didn't find any threads actually blocked on a lock
* so we have nothing to do except context switch away.
*/
counter_u64_add(switch_count, 1);
mi_switch(SW_VOL | SWT_RELINQUISH);
/*
* It is important the thread lock is dropped while yielding
* to allow other threads to acquire the lock pointed to by
* TDQ_LOCKPTR(td). Currently mi_switch() will unlock the
* thread lock before returning. Else a deadlock like
* situation might happen.
*/
thread_lock(td);
}
void
epoch_wait_preempt(epoch_t epoch)
{
struct thread *td;
int was_bound;
int old_cpu;
int old_pinned;
u_char old_prio;
int locks __unused;
MPASS(cold || epoch != NULL);
INIT_CHECK(epoch);
td = curthread;
#ifdef INVARIANTS
locks = curthread->td_locks;
MPASS(epoch->e_flags & EPOCH_PREEMPT);
if ((epoch->e_flags & EPOCH_LOCKED) == 0)
WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL,
"epoch_wait() can be long running");
KASSERT(!in_epoch(epoch), ("epoch_wait_preempt() called in the middle "
"of an epoch section of the same epoch"));
#endif
DROP_GIANT();
thread_lock(td);
old_cpu = PCPU_GET(cpuid);
old_pinned = td->td_pinned;
old_prio = td->td_priority;
was_bound = sched_is_bound(td);
sched_unbind(td);
td->td_pinned = 0;
sched_bind(td, old_cpu);
ck_epoch_synchronize_wait(&epoch->e_epoch, epoch_block_handler_preempt,
NULL);
/* restore CPU binding, if any */
if (was_bound != 0) {
sched_bind(td, old_cpu);
} else {
/* get thread back to initial CPU, if any */
if (old_pinned != 0)
sched_bind(td, old_cpu);
sched_unbind(td);
}
/* restore pinned after bind */
td->td_pinned = old_pinned;
/* restore thread priority */
sched_prio(td, old_prio);
thread_unlock(td);
PICKUP_GIANT();
KASSERT(td->td_locks == locks,
("%d residual locks held", td->td_locks - locks));
}
static void
epoch_block_handler(struct ck_epoch *g __unused, ck_epoch_record_t *c __unused,
void *arg __unused)
{
cpu_spinwait();
}
void
epoch_wait(epoch_t epoch)
{
MPASS(cold || epoch != NULL);
INIT_CHECK(epoch);
MPASS(epoch->e_flags == 0);
critical_enter();
ck_epoch_synchronize_wait(&epoch->e_epoch, epoch_block_handler, NULL);
critical_exit();
}
void
epoch_call(epoch_t epoch, epoch_callback_t callback, epoch_context_t ctx)
{
epoch_record_t er;
ck_epoch_entry_t *cb;
cb = (void *)ctx;
MPASS(callback);
/* too early in boot to have epoch set up */
if (__predict_false(epoch == NULL))
goto boottime;
#if !defined(EARLY_AP_STARTUP)
if (__predict_false(inited < 2))
goto boottime;
#endif
critical_enter();
*DPCPU_PTR(epoch_cb_count) += 1;
er = epoch_currecord(epoch);
ck_epoch_call(&er->er_record, cb, (ck_epoch_cb_t *)callback);
critical_exit();
return;
boottime:
callback(ctx);
}
static void
epoch_call_task(void *arg __unused)
{
ck_stack_entry_t *cursor, *head, *next;
ck_epoch_record_t *record;
epoch_record_t er;
epoch_t epoch;
ck_stack_t cb_stack;
int i, npending, total;
ck_stack_init(&cb_stack);
critical_enter();
epoch_enter(global_epoch);
for (total = i = 0; i != MAX_EPOCHS; i++) {
epoch = epoch_array + i;
if (__predict_false(
atomic_load_acq_int(&epoch->e_in_use) == 0))
continue;
er = epoch_currecord(epoch);
record = &er->er_record;
if ((npending = record->n_pending) == 0)
continue;
ck_epoch_poll_deferred(record, &cb_stack);
total += npending - record->n_pending;
}
epoch_exit(global_epoch);
*DPCPU_PTR(epoch_cb_count) -= total;
critical_exit();
counter_u64_add(epoch_call_count, total);
counter_u64_add(epoch_call_task_count, 1);
head = ck_stack_batch_pop_npsc(&cb_stack);
for (cursor = head; cursor != NULL; cursor = next) {
struct ck_epoch_entry *entry =
ck_epoch_entry_container(cursor);
next = CK_STACK_NEXT(cursor);
entry->function(entry);
}
}
static int
in_epoch_verbose_preempt(epoch_t epoch, int dump_onfail)
{
epoch_record_t er;
struct epoch_tracker *tdwait;
struct thread *td;
MPASS(epoch != NULL);
MPASS((epoch->e_flags & EPOCH_PREEMPT) != 0);
td = curthread;
if (THREAD_CAN_SLEEP())
return (0);
critical_enter();
er = epoch_currecord(epoch);
TAILQ_FOREACH(tdwait, &er->er_tdlist, et_link)
if (tdwait->et_td == td) {
critical_exit();
return (1);
}
#ifdef INVARIANTS
if (dump_onfail) {
MPASS(td->td_pinned);
printf("cpu: %d id: %d\n", curcpu, td->td_tid);
TAILQ_FOREACH(tdwait, &er->er_tdlist, et_link)
printf("td_tid: %d ", tdwait->et_td->td_tid);
printf("\n");
}
#endif
critical_exit();
return (0);
}
#ifdef INVARIANTS
static void
epoch_assert_nocpu(epoch_t epoch, struct thread *td)
{
epoch_record_t er;
int cpu;
bool crit;
crit = td->td_critnest > 0;
/* Check for a critical section mishap. */
CPU_FOREACH(cpu) {
er = zpcpu_get_cpu(epoch->e_pcpu_record, cpu);
KASSERT(er->er_td != td,
("%s critical section in epoch '%s', from cpu %d",
(crit ? "exited" : "re-entered"), epoch->e_name, cpu));
}
}
#else
#define epoch_assert_nocpu(e, td) do {} while (0)
#endif
int
in_epoch_verbose(epoch_t epoch, int dump_onfail)
{
epoch_record_t er;
struct thread *td;
if (__predict_false((epoch) == NULL))
return (0);
if ((epoch->e_flags & EPOCH_PREEMPT) != 0)
return (in_epoch_verbose_preempt(epoch, dump_onfail));
/*
* The thread being in a critical section is a necessary
* condition to be correctly inside a non-preemptible epoch,
* so it's definitely not in this epoch.
*/
td = curthread;
if (td->td_critnest == 0) {
epoch_assert_nocpu(epoch, td);
return (0);
}
/*
* The current cpu is in a critical section, so the epoch record will be
* stable for the rest of this function. Knowing that the record is not
* active is sufficient for knowing whether we're in this epoch or not,
* since it's a pcpu record.
*/
er = epoch_currecord(epoch);
if (er->er_record.active == 0) {
epoch_assert_nocpu(epoch, td);
return (0);
}
MPASS(er->er_td == td);
return (1);
}
int
in_epoch(epoch_t epoch)
{
return (in_epoch_verbose(epoch, 0));
}
static void
epoch_drain_cb(struct epoch_context *ctx)
{
struct epoch *epoch =
__containerof(ctx, struct epoch_record, er_drain_ctx)->er_parent;
if (atomic_fetchadd_int(&epoch->e_drain_count, -1) == 1) {
mtx_lock(&epoch->e_drain_mtx);
wakeup(epoch);
mtx_unlock(&epoch->e_drain_mtx);
}
}
void
epoch_drain_callbacks(epoch_t epoch)
{
epoch_record_t er;
struct thread *td;
int was_bound;
int old_pinned;
int old_cpu;
int cpu;
WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL,
"epoch_drain_callbacks() may sleep!");
/* too early in boot to have epoch set up */
if (__predict_false(epoch == NULL))
return;
#if !defined(EARLY_AP_STARTUP)
if (__predict_false(inited < 2))
return;
#endif
DROP_GIANT();
sx_xlock(&epoch->e_drain_sx);
mtx_lock(&epoch->e_drain_mtx);
td = curthread;
thread_lock(td);
old_cpu = PCPU_GET(cpuid);
old_pinned = td->td_pinned;
was_bound = sched_is_bound(td);
sched_unbind(td);
td->td_pinned = 0;
CPU_FOREACH(cpu)
epoch->e_drain_count++;
CPU_FOREACH(cpu) {
er = zpcpu_get_cpu(epoch->e_pcpu_record, cpu);
sched_bind(td, cpu);
epoch_call(epoch, &epoch_drain_cb, &er->er_drain_ctx);
}
/* restore CPU binding, if any */
if (was_bound != 0) {
sched_bind(td, old_cpu);
} else {
/* get thread back to initial CPU, if any */
if (old_pinned != 0)
sched_bind(td, old_cpu);
sched_unbind(td);
}
/* restore pinned after bind */
td->td_pinned = old_pinned;
thread_unlock(td);
while (epoch->e_drain_count != 0)
msleep(epoch, &epoch->e_drain_mtx, PZERO, "EDRAIN", 0);
mtx_unlock(&epoch->e_drain_mtx);
sx_xunlock(&epoch->e_drain_sx);
PICKUP_GIANT();
}