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/*
*
* Copyright 2016, Google Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * 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.
* * Neither the name of Google Inc. nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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 COPYRIGHT
* OWNER 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 "src/core/lib/iomgr/combiner.h"
#include <assert.h>
#include <string.h>
#include <grpc/support/alloc.h>
#include <grpc/support/log.h>
#include "src/core/lib/iomgr/workqueue.h"
#include "src/core/lib/profiling/timers.h"
int grpc_combiner_trace = 0;
#define GRPC_COMBINER_TRACE(fn) \
do { \
if (grpc_combiner_trace) { \
fn; \
} \
} while (0)
#define STATE_UNORPHANED 1
#define STATE_ELEM_COUNT_LOW_BIT 2
struct grpc_combiner {
grpc_combiner *next_combiner_on_this_exec_ctx;
grpc_workqueue *optional_workqueue;
grpc_closure_scheduler uncovered_scheduler;
grpc_closure_scheduler covered_scheduler;
grpc_closure_scheduler uncovered_finally_scheduler;
grpc_closure_scheduler covered_finally_scheduler;
gpr_mpscq queue;
// state is:
// lower bit - zero if orphaned (STATE_UNORPHANED)
// other bits - number of items queued on the lock (STATE_ELEM_COUNT_LOW_BIT)
gpr_atm state;
// number of elements in the list that are covered by a poller: if >0, we can
// offload safely
gpr_atm elements_covered_by_poller;
bool time_to_execute_final_list;
bool final_list_covered_by_poller;
grpc_closure_list final_list;
grpc_closure offload;
gpr_refcount refs;
};
static void combiner_exec_uncovered(grpc_exec_ctx *exec_ctx,
grpc_closure *closure, grpc_error *error);
static void combiner_exec_covered(grpc_exec_ctx *exec_ctx,
grpc_closure *closure, grpc_error *error);
static void combiner_finally_exec_uncovered(grpc_exec_ctx *exec_ctx,
grpc_closure *closure,
grpc_error *error);
static void combiner_finally_exec_covered(grpc_exec_ctx *exec_ctx,
grpc_closure *closure,
grpc_error *error);
static const grpc_closure_scheduler_vtable scheduler_uncovered = {
combiner_exec_uncovered, combiner_exec_uncovered,
"combiner:immediately:uncovered"};
static const grpc_closure_scheduler_vtable scheduler_covered = {
combiner_exec_covered, combiner_exec_covered,
"combiner:immediately:covered"};
static const grpc_closure_scheduler_vtable finally_scheduler_uncovered = {
combiner_finally_exec_uncovered, combiner_finally_exec_uncovered,
"combiner:finally:uncovered"};
static const grpc_closure_scheduler_vtable finally_scheduler_covered = {
combiner_finally_exec_covered, combiner_finally_exec_covered,
"combiner:finally:covered"};
static void offload(grpc_exec_ctx *exec_ctx, void *arg, grpc_error *error);
typedef struct {
grpc_error *error;
bool covered_by_poller;
} error_data;
static uintptr_t pack_error_data(error_data d) {
return ((uintptr_t)d.error) | (d.covered_by_poller ? 1 : 0);
}
static error_data unpack_error_data(uintptr_t p) {
return (error_data){(grpc_error *)(p & ~(uintptr_t)1), p & 1};
}
static bool is_covered_by_poller(grpc_combiner *lock) {
return lock->final_list_covered_by_poller ||
gpr_atm_acq_load(&lock->elements_covered_by_poller) > 0;
}
#define IS_COVERED_BY_POLLER_FMT "(final=%d elems=%" PRIdPTR ")->%d"
#define IS_COVERED_BY_POLLER_ARGS(lock) \
(lock)->final_list_covered_by_poller, \
gpr_atm_acq_load(&(lock)->elements_covered_by_poller), \
is_covered_by_poller((lock))
grpc_combiner *grpc_combiner_create(grpc_workqueue *optional_workqueue) {
grpc_combiner *lock = gpr_malloc(sizeof(*lock));
gpr_ref_init(&lock->refs, 1);
lock->next_combiner_on_this_exec_ctx = NULL;
lock->time_to_execute_final_list = false;
lock->optional_workqueue = optional_workqueue;
lock->final_list_covered_by_poller = false;
lock->uncovered_scheduler.vtable = &scheduler_uncovered;
lock->covered_scheduler.vtable = &scheduler_covered;
lock->uncovered_finally_scheduler.vtable = &finally_scheduler_uncovered;
lock->covered_finally_scheduler.vtable = &finally_scheduler_covered;
gpr_atm_no_barrier_store(&lock->state, STATE_UNORPHANED);
gpr_atm_no_barrier_store(&lock->elements_covered_by_poller, 0);
gpr_mpscq_init(&lock->queue);
grpc_closure_list_init(&lock->final_list);
grpc_closure_init(&lock->offload, offload, lock,
grpc_workqueue_scheduler(lock->optional_workqueue));
GRPC_COMBINER_TRACE(gpr_log(GPR_DEBUG, "C:%p create", lock));
return lock;
}
static void really_destroy(grpc_exec_ctx *exec_ctx, grpc_combiner *lock) {
GRPC_COMBINER_TRACE(gpr_log(GPR_DEBUG, "C:%p really_destroy", lock));
GPR_ASSERT(gpr_atm_no_barrier_load(&lock->state) == 0);
gpr_mpscq_destroy(&lock->queue);
GRPC_WORKQUEUE_UNREF(exec_ctx, lock->optional_workqueue, "combiner");
gpr_free(lock);
}
static void start_destroy(grpc_exec_ctx *exec_ctx, grpc_combiner *lock) {
gpr_atm old_state = gpr_atm_full_fetch_add(&lock->state, -STATE_UNORPHANED);
GRPC_COMBINER_TRACE(gpr_log(
GPR_DEBUG, "C:%p really_destroy old_state=%" PRIdPTR, lock, old_state));
if (old_state == 1) {
really_destroy(exec_ctx, lock);
}
}
#ifdef GRPC_COMBINER_REFCOUNT_DEBUG
#define GRPC_COMBINER_DEBUG_SPAM(op, delta) \
gpr_log(file, line, GPR_LOG_SEVERITY_DEBUG, \
"combiner[%p] %s %" PRIdPTR " --> %" PRIdPTR " %s", lock, (op), \
gpr_atm_no_barrier_load(&lock->refs.count), \
gpr_atm_no_barrier_load(&lock->refs.count) + (delta), reason);
#else
#define GRPC_COMBINER_DEBUG_SPAM(op, delta)
#endif
void grpc_combiner_unref(grpc_exec_ctx *exec_ctx,
grpc_combiner *lock GRPC_COMBINER_DEBUG_ARGS) {
GRPC_COMBINER_DEBUG_SPAM("UNREF", -1);
if (gpr_unref(&lock->refs)) {
start_destroy(exec_ctx, lock);
}
}
grpc_combiner *grpc_combiner_ref(grpc_combiner *lock GRPC_COMBINER_DEBUG_ARGS) {
GRPC_COMBINER_DEBUG_SPAM(" REF", 1);
gpr_ref(&lock->refs);
return lock;
}
static void push_last_on_exec_ctx(grpc_exec_ctx *exec_ctx,
grpc_combiner *lock) {
lock->next_combiner_on_this_exec_ctx = NULL;
if (exec_ctx->active_combiner == NULL) {
exec_ctx->active_combiner = exec_ctx->last_combiner = lock;
} else {
exec_ctx->last_combiner->next_combiner_on_this_exec_ctx = lock;
exec_ctx->last_combiner = lock;
}
}
static void push_first_on_exec_ctx(grpc_exec_ctx *exec_ctx,
grpc_combiner *lock) {
lock->next_combiner_on_this_exec_ctx = exec_ctx->active_combiner;
exec_ctx->active_combiner = lock;
if (lock->next_combiner_on_this_exec_ctx == NULL) {
exec_ctx->last_combiner = lock;
}
}
static void combiner_exec(grpc_exec_ctx *exec_ctx, grpc_combiner *lock,
grpc_closure *cl, grpc_error *error,
bool covered_by_poller) {
GPR_TIMER_BEGIN("combiner.execute", 0);
gpr_atm last = gpr_atm_full_fetch_add(&lock->state, STATE_ELEM_COUNT_LOW_BIT);
GRPC_COMBINER_TRACE(gpr_log(
GPR_DEBUG, "C:%p grpc_combiner_execute c=%p cov=%d last=%" PRIdPTR, lock,
cl, covered_by_poller, last));
GPR_ASSERT(last & STATE_UNORPHANED); // ensure lock has not been destroyed
assert(cl->cb);
cl->error_data.scratch =
pack_error_data((error_data){error, covered_by_poller});
if (covered_by_poller) {
gpr_atm_no_barrier_fetch_add(&lock->elements_covered_by_poller, 1);
}
gpr_mpscq_push(&lock->queue, &cl->next_data.atm_next);
if (last == 1) {
// first element on this list: add it to the list of combiner locks
// executing within this exec_ctx
push_last_on_exec_ctx(exec_ctx, lock);
}
GPR_TIMER_END("combiner.execute", 0);
}
#define COMBINER_FROM_CLOSURE_SCHEDULER(closure, scheduler_name) \
((grpc_combiner *)(((char *)((closure)->scheduler)) - \
offsetof(grpc_combiner, scheduler_name)))
static void combiner_exec_uncovered(grpc_exec_ctx *exec_ctx, grpc_closure *cl,
grpc_error *error) {
combiner_exec(exec_ctx,
COMBINER_FROM_CLOSURE_SCHEDULER(cl, uncovered_scheduler), cl,
error, false);
}
static void combiner_exec_covered(grpc_exec_ctx *exec_ctx, grpc_closure *cl,
grpc_error *error) {
combiner_exec(exec_ctx,
COMBINER_FROM_CLOSURE_SCHEDULER(cl, covered_scheduler), cl,
error, true);
}
static void move_next(grpc_exec_ctx *exec_ctx) {
exec_ctx->active_combiner =
exec_ctx->active_combiner->next_combiner_on_this_exec_ctx;
if (exec_ctx->active_combiner == NULL) {
exec_ctx->last_combiner = NULL;
}
}
static void offload(grpc_exec_ctx *exec_ctx, void *arg, grpc_error *error) {
grpc_combiner *lock = arg;
push_last_on_exec_ctx(exec_ctx, lock);
}
static void queue_offload(grpc_exec_ctx *exec_ctx, grpc_combiner *lock) {
move_next(exec_ctx);
GRPC_COMBINER_TRACE(gpr_log(GPR_DEBUG, "C:%p queue_offload --> %p", lock,
lock->optional_workqueue));
grpc_closure_sched(exec_ctx, &lock->offload, GRPC_ERROR_NONE);
}
bool grpc_combiner_continue_exec_ctx(grpc_exec_ctx *exec_ctx) {
GPR_TIMER_BEGIN("combiner.continue_exec_ctx", 0);
grpc_combiner *lock = exec_ctx->active_combiner;
if (lock == NULL) {
GPR_TIMER_END("combiner.continue_exec_ctx", 0);
return false;
}
GRPC_COMBINER_TRACE(
gpr_log(GPR_DEBUG,
"C:%p grpc_combiner_continue_exec_ctx workqueue=%p "
"is_covered_by_poller=" IS_COVERED_BY_POLLER_FMT
" exec_ctx_ready_to_finish=%d "
"time_to_execute_final_list=%d",
lock, lock->optional_workqueue, IS_COVERED_BY_POLLER_ARGS(lock),
grpc_exec_ctx_ready_to_finish(exec_ctx),
lock->time_to_execute_final_list));
if (lock->optional_workqueue != NULL && is_covered_by_poller(lock) &&
grpc_exec_ctx_ready_to_finish(exec_ctx)) {
GPR_TIMER_MARK("offload_from_finished_exec_ctx", 0);
// this execution context wants to move on, and we have a workqueue (and
// so can help the execution context out): schedule remaining work to be
// picked up on the workqueue
queue_offload(exec_ctx, lock);
GPR_TIMER_END("combiner.continue_exec_ctx", 0);
return true;
}
if (!lock->time_to_execute_final_list ||
// peek to see if something new has shown up, and execute that with
// priority
(gpr_atm_acq_load(&lock->state) >> 1) > 1) {
gpr_mpscq_node *n = gpr_mpscq_pop(&lock->queue);
GRPC_COMBINER_TRACE(
gpr_log(GPR_DEBUG, "C:%p maybe_finish_one n=%p", lock, n));
if (n == NULL) {
// queue is in an inconsistent state: use this as a cue that we should
// go off and do something else for a while (and come back later)
GPR_TIMER_MARK("delay_busy", 0);
if (lock->optional_workqueue != NULL && is_covered_by_poller(lock)) {
queue_offload(exec_ctx, lock);
}
GPR_TIMER_END("combiner.continue_exec_ctx", 0);
return true;
}
GPR_TIMER_BEGIN("combiner.exec1", 0);
grpc_closure *cl = (grpc_closure *)n;
error_data err = unpack_error_data(cl->error_data.scratch);
#ifndef NDEBUG
cl->scheduled = false;
#endif
cl->cb(exec_ctx, cl->cb_arg, err.error);
if (err.covered_by_poller) {
gpr_atm_no_barrier_fetch_add(&lock->elements_covered_by_poller, -1);
}
GRPC_ERROR_UNREF(err.error);
GPR_TIMER_END("combiner.exec1", 0);
} else {
grpc_closure *c = lock->final_list.head;
GPR_ASSERT(c != NULL);
grpc_closure_list_init(&lock->final_list);
lock->final_list_covered_by_poller = false;
int loops = 0;
while (c != NULL) {
GPR_TIMER_BEGIN("combiner.exec_1final", 0);
GRPC_COMBINER_TRACE(
gpr_log(GPR_DEBUG, "C:%p execute_final[%d] c=%p", lock, loops, c));
grpc_closure *next = c->next_data.next;
grpc_error *error = c->error_data.error;
#ifndef NDEBUG
c->scheduled = false;
#endif
c->cb(exec_ctx, c->cb_arg, error);
GRPC_ERROR_UNREF(error);
c = next;
GPR_TIMER_END("combiner.exec_1final", 0);
}
}
GPR_TIMER_MARK("unref", 0);
move_next(exec_ctx);
lock->time_to_execute_final_list = false;
gpr_atm old_state =
gpr_atm_full_fetch_add(&lock->state, -STATE_ELEM_COUNT_LOW_BIT);
GRPC_COMBINER_TRACE(
gpr_log(GPR_DEBUG, "C:%p finish old_state=%" PRIdPTR, lock, old_state));
// Define a macro to ease readability of the following switch statement.
#define OLD_STATE_WAS(orphaned, elem_count) \
(((orphaned) ? 0 : STATE_UNORPHANED) | \
((elem_count)*STATE_ELEM_COUNT_LOW_BIT))
// Depending on what the previous state was, we need to perform different
// actions.
switch (old_state) {
default:
// we have multiple queued work items: just continue executing them
break;
case OLD_STATE_WAS(false, 2):
case OLD_STATE_WAS(true, 2):
// we're down to one queued item: if it's the final list we should do that
if (!grpc_closure_list_empty(lock->final_list)) {
lock->time_to_execute_final_list = true;
}
break;
case OLD_STATE_WAS(false, 1):
// had one count, one unorphaned --> unlocked unorphaned
GPR_TIMER_END("combiner.continue_exec_ctx", 0);
return true;
case OLD_STATE_WAS(true, 1):
// and one count, one orphaned --> unlocked and orphaned
really_destroy(exec_ctx, lock);
GPR_TIMER_END("combiner.continue_exec_ctx", 0);
return true;
case OLD_STATE_WAS(false, 0):
case OLD_STATE_WAS(true, 0):
// these values are illegal - representing an already unlocked or
// deleted lock
GPR_TIMER_END("combiner.continue_exec_ctx", 0);
GPR_UNREACHABLE_CODE(return true);
}
push_first_on_exec_ctx(exec_ctx, lock);
GPR_TIMER_END("combiner.continue_exec_ctx", 0);
return true;
}
static void enqueue_finally(grpc_exec_ctx *exec_ctx, void *closure,
grpc_error *error);
static void combiner_execute_finally(grpc_exec_ctx *exec_ctx,
grpc_combiner *lock, grpc_closure *closure,
grpc_error *error,
bool covered_by_poller) {
GRPC_COMBINER_TRACE(gpr_log(
GPR_DEBUG, "C:%p grpc_combiner_execute_finally c=%p; ac=%p; cov=%d", lock,
closure, exec_ctx->active_combiner, covered_by_poller));
GPR_TIMER_BEGIN("combiner.execute_finally", 0);
if (exec_ctx->active_combiner != lock) {
GPR_TIMER_MARK("slowpath", 0);
grpc_closure_sched(
exec_ctx, grpc_closure_create(enqueue_finally, closure,
grpc_combiner_scheduler(lock, false)),
error);
GPR_TIMER_END("combiner.execute_finally", 0);
return;
}
if (grpc_closure_list_empty(lock->final_list)) {
gpr_atm_full_fetch_add(&lock->state, STATE_ELEM_COUNT_LOW_BIT);
}
if (covered_by_poller) {
lock->final_list_covered_by_poller = true;
}
grpc_closure_list_append(&lock->final_list, closure, error);
GPR_TIMER_END("combiner.execute_finally", 0);
}
static void enqueue_finally(grpc_exec_ctx *exec_ctx, void *closure,
grpc_error *error) {
combiner_execute_finally(exec_ctx, exec_ctx->active_combiner, closure,
GRPC_ERROR_REF(error), false);
}
static void combiner_finally_exec_uncovered(grpc_exec_ctx *exec_ctx,
grpc_closure *cl,
grpc_error *error) {
combiner_execute_finally(exec_ctx, COMBINER_FROM_CLOSURE_SCHEDULER(
cl, uncovered_finally_scheduler),
cl, error, false);
}
static void combiner_finally_exec_covered(grpc_exec_ctx *exec_ctx,
grpc_closure *cl, grpc_error *error) {
combiner_execute_finally(
exec_ctx, COMBINER_FROM_CLOSURE_SCHEDULER(cl, covered_finally_scheduler),
cl, error, true);
}
grpc_closure_scheduler *grpc_combiner_scheduler(grpc_combiner *combiner,
bool covered_by_poller) {
return covered_by_poller ? &combiner->covered_scheduler
: &combiner->uncovered_scheduler;
}
grpc_closure_scheduler *grpc_combiner_finally_scheduler(
grpc_combiner *combiner, bool covered_by_poller) {
return covered_by_poller ? &combiner->covered_finally_scheduler
: &combiner->uncovered_finally_scheduler;
}
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