freebsd-dev/sys/kern/subr_epoch.c
Hans Petter Selasky ef0f7ae934 The old thread priority must be stored as part of the EPOCH(9) tracker.
Else recursive use of EPOCH(9) may cause the wrong priority to be restored.

Bump the __FreeBSD_version due to changing the thread and epoch tracker
structure.

Differential Revision:	https://reviews.freebsd.org/D30375
Reviewed by:	markj@
MFC after:	1 week
Sponsored by:	Mellanox Technologies // NVIDIA Networking
2021-05-23 10:53:25 +02:00

997 lines
25 KiB
C

/*-
* SPDX-License-Identifier: BSD-2-Clause-FreeBSD
*
* 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>
__FBSDID("$FreeBSD$");
#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 <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)
#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_zero(&se.se_stack); /* XXX: is it really needed? */
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;
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);
}
/* 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);
}
#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();
}
static epoch_record_t
epoch_currecord(epoch_t epoch)
{
return (zpcpu_get(epoch->e_pcpu_record));
}
#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((vm_offset_t)et >= td->td_kstack &&
(vm_offset_t)et + sizeof(struct epoch_tracker) <=
td->td_kstack + td->td_kstack_pages * PAGE_SIZE);
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();
}