src/core/lib/iomgr/exec_ctx.cc

/*
 *
 * Copyright 2015 gRPC authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */

#include "src/core/lib/iomgr/exec_ctx.h"

#include <grpc/support/log.h>
#include <grpc/support/sync.h>
#include <grpc/support/thd.h>

#include "src/core/lib/iomgr/combiner.h"
#include "src/core/lib/profiling/timers.h"

#define GRPC_START_TIME_UPDATE_INTERVAL 10000
extern "C" grpc_tracer_flag grpc_timer_check_trace;

bool grpc_exec_ctx_ready_to_finish(grpc_exec_ctx* exec_ctx) {
  if ((exec_ctx->flags & GRPC_EXEC_CTX_FLAG_IS_FINISHED) == 0) {
    if (exec_ctx->check_ready_to_finish(exec_ctx,
                                        exec_ctx->check_ready_to_finish_arg)) {
      exec_ctx->flags |= GRPC_EXEC_CTX_FLAG_IS_FINISHED;
      return true;
    }
    return false;
  } else {
    return true;
  }
}

bool grpc_never_ready_to_finish(grpc_exec_ctx* exec_ctx, void* arg_ignored) {
  return false;
}

bool grpc_always_ready_to_finish(grpc_exec_ctx* exec_ctx, void* arg_ignored) {
  return true;
}

bool grpc_exec_ctx_has_work(grpc_exec_ctx* exec_ctx) {
  return exec_ctx->active_combiner != NULL ||
         !grpc_closure_list_empty(exec_ctx->closure_list);
}

void grpc_exec_ctx_finish(grpc_exec_ctx* exec_ctx) {
  exec_ctx->flags |= GRPC_EXEC_CTX_FLAG_IS_FINISHED;
  grpc_exec_ctx_flush(exec_ctx);
}

static void exec_ctx_run(grpc_exec_ctx* exec_ctx, grpc_closure* closure,
                         grpc_error* error) {
#ifndef NDEBUG
  closure->scheduled = false;
  if (GRPC_TRACER_ON(grpc_trace_closure)) {
    gpr_log(GPR_DEBUG, "running closure %p: created [%s:%d]: %s [%s:%d]",
            closure, closure->file_created, closure->line_created,
            closure->run ? "run" : "scheduled", closure->file_initiated,
            closure->line_initiated);
  }
#endif
  closure->cb(exec_ctx, closure->cb_arg, error);
#ifndef NDEBUG
  if (GRPC_TRACER_ON(grpc_trace_closure)) {
    gpr_log(GPR_DEBUG, "closure %p finished", closure);
  }
#endif
  GRPC_ERROR_UNREF(error);
}

bool grpc_exec_ctx_flush(grpc_exec_ctx* exec_ctx) {
  bool did_something = 0;
  GPR_TIMER_BEGIN("grpc_exec_ctx_flush", 0);
  for (;;) {
    if (!grpc_closure_list_empty(exec_ctx->closure_list)) {
      grpc_closure* c = exec_ctx->closure_list.head;
      exec_ctx->closure_list.head = exec_ctx->closure_list.tail = NULL;
      while (c != NULL) {
        grpc_closure* next = c->next_data.next;
        grpc_error* error = c->error_data.error;
        did_something = true;
        exec_ctx_run(exec_ctx, c, error);
        c = next;
      }
    } else if (!grpc_combiner_continue_exec_ctx(exec_ctx)) {
      break;
    }
  }
  GPR_ASSERT(exec_ctx->active_combiner == NULL);
  GPR_TIMER_END("grpc_exec_ctx_flush", 0);
  return did_something;
}

static void exec_ctx_sched(grpc_exec_ctx* exec_ctx, grpc_closure* closure,
                           grpc_error* error) {
  grpc_closure_list_append(&exec_ctx->closure_list, closure, error);
}

static gpr_timespec
    g_start_time[GPR_TIMESPAN + 1];  // assumes GPR_TIMESPAN is the
                                     // last enum value in
                                     // gpr_clock_type

static grpc_millis g_last_start_time_update;
static gpr_mu g_start_time_mu;

void grpc_exec_ctx_global_init(void) {
  for (int i = 0; i < GPR_TIMESPAN; i++) {
    g_start_time[i] = gpr_now((gpr_clock_type)i);
  }
  // allows uniform treatment in conversion functions
  g_start_time[GPR_TIMESPAN] = gpr_time_0(GPR_TIMESPAN);
  gpr_mu_init(&g_start_time_mu);
}

void grpc_exec_ctx_global_shutdown(void) {}

static gpr_atm timespec_to_atm_round_down(gpr_timespec ts) {
  ts = gpr_time_sub(ts, g_start_time[ts.clock_type]);
  double x =
      GPR_MS_PER_SEC * (double)ts.tv_sec + (double)ts.tv_nsec / GPR_NS_PER_MS;
  if (x < 0) return 0;
  if (x > GPR_ATM_MAX) return GPR_ATM_MAX;
  return (gpr_atm)x;
}

static gpr_atm timespec_to_atm_round_up(gpr_timespec ts) {
  ts = gpr_time_sub(ts, g_start_time[ts.clock_type]);
  double x = GPR_MS_PER_SEC * (double)ts.tv_sec +
             (double)ts.tv_nsec / GPR_NS_PER_MS +
             (double)(GPR_NS_PER_SEC - 1) / (double)GPR_NS_PER_SEC;
  if (x < 0) return 0;
  if (x > GPR_ATM_MAX) return GPR_ATM_MAX;
  return (gpr_atm)x;
}

grpc_millis grpc_exec_ctx_now(grpc_exec_ctx* exec_ctx) {
  if (!exec_ctx->now_is_valid) {
    exec_ctx->now = timespec_to_atm_round_down(gpr_now(GPR_CLOCK_MONOTONIC));
    exec_ctx->now_is_valid = true;
  }
  return exec_ctx->now;
}

void grpc_exec_ctx_invalidate_now(grpc_exec_ctx* exec_ctx) {
  exec_ctx->now_is_valid = false;
}

gpr_timespec grpc_millis_to_timespec(grpc_millis millis,
                                     gpr_clock_type clock_type) {
  // special-case infinities as grpc_millis can be 32bit on some platforms
  // while gpr_time_from_millis always takes an int64_t.
  if (millis == GRPC_MILLIS_INF_FUTURE) {
    return gpr_inf_future(clock_type);
  }
  if (millis == GRPC_MILLIS_INF_PAST) {
    return gpr_inf_past(clock_type);
  }

  if (clock_type == GPR_TIMESPAN) {
    return gpr_time_from_millis(millis, GPR_TIMESPAN);
  }
  return gpr_time_add(g_start_time[clock_type],
                      gpr_time_from_millis(millis, GPR_TIMESPAN));
}

grpc_millis grpc_timespec_to_millis_round_down(gpr_timespec ts) {
  return timespec_to_atm_round_down(ts);
}

grpc_millis grpc_timespec_to_millis_round_up(gpr_timespec ts) {
  return timespec_to_atm_round_up(ts);
}

void grpc_exec_ctx_maybe_update_start_time(grpc_exec_ctx* exec_ctx) {
  grpc_exec_ctx_invalidate_now(exec_ctx);
  grpc_millis now = grpc_exec_ctx_now(exec_ctx);
  grpc_millis last_start_time_update = gpr_atm_acq_load(&g_last_start_time_update);
  if (now > last_start_time_update &&
      now - last_start_time_update > GRPC_START_TIME_UPDATE_INTERVAL) {
    gpr_timespec real_now = gpr_now(GPR_CLOCK_REALTIME);
    gpr_timespec old_now = grpc_millis_to_timespec(now, GPR_CLOCK_REALTIME);
    gpr_timespec diff = gpr_time_sub(real_now, old_now);
    if (GRPC_TRACER_ON(grpc_timer_check_trace)) {
      gpr_log(GPR_DEBUG, "Update start time with diff: %" PRId64 "s %dns", diff.tv_sec, diff.tv_nsec);
    }
    gpr_mu_lock(&g_start_time_mu);
    if (last_start_time_update == gpr_atm_acq_load(&g_last_start_time_update)) {
      g_start_time[GPR_CLOCK_REALTIME] = gpr_time_add(g_start_time[GPR_CLOCK_REALTIME], diff);
      g_last_start_time_update = now;
    }
    gpr_mu_unlock(&g_start_time_mu);
  }
}

static const grpc_closure_scheduler_vtable exec_ctx_scheduler_vtable = {
    exec_ctx_run, exec_ctx_sched, "exec_ctx"};
static grpc_closure_scheduler exec_ctx_scheduler = {&exec_ctx_scheduler_vtable};
grpc_closure_scheduler* grpc_schedule_on_exec_ctx = &exec_ctx_scheduler;