Merge pull request #12413 from sreecha/fix-epoll1-bug

Fix epoll1 hang
reviewable/pr11758/r1
Sree Kuchibhotla 8 years ago committed by GitHub
commit f54af4832e
  1. 45
      src/core/lib/iomgr/ev_epoll1_linux.c

@ -698,22 +698,30 @@ static bool begin_worker(grpc_pollset *pollset, grpc_pollset_worker *worker,
gpr_mu_unlock(&pollset->mu);
goto retry_lock_neighbourhood;
}
pollset->seen_inactive = false;
if (neighbourhood->active_root == NULL) {
neighbourhood->active_root = pollset->next = pollset->prev = pollset;
/* TODO: sreek. Why would this worker state be other than UNKICKED
* here ? (since the worker isn't added to the pollset yet, there is no
* way it can be "found" by other threads to get kicked). */
/* If there is no designated poller, make this the designated poller */
if (worker->kick_state == UNKICKED &&
gpr_atm_no_barrier_cas(&g_active_poller, 0, (gpr_atm)worker)) {
SET_KICK_STATE(worker, DESIGNATED_POLLER);
/* In the brief time we released the pollset locks above, the worker MAY
have been kicked. In this case, the worker should get out of this
pollset ASAP and hence this should neither add the pollset to
neighbourhood nor mark the pollset as active.
On a side note, the only way a worker's kick state could have changed
at this point is if it were "kicked specifically". Since the worker has
not added itself to the pollset yet (by calling worker_insert()), it is
not visible in the "kick any" path yet */
if (worker->kick_state == UNKICKED) {
pollset->seen_inactive = false;
if (neighbourhood->active_root == NULL) {
neighbourhood->active_root = pollset->next = pollset->prev = pollset;
/* Make this the designated poller if there isn't one already */
if (worker->kick_state == UNKICKED &&
gpr_atm_no_barrier_cas(&g_active_poller, 0, (gpr_atm)worker)) {
SET_KICK_STATE(worker, DESIGNATED_POLLER);
}
} else {
pollset->next = neighbourhood->active_root;
pollset->prev = pollset->next->prev;
pollset->next->prev = pollset->prev->next = pollset;
}
} else {
pollset->next = neighbourhood->active_root;
pollset->prev = pollset->next->prev;
pollset->next->prev = pollset->prev->next = pollset;
}
}
if (is_reassigning) {
@ -1001,6 +1009,7 @@ static grpc_error *pollset_kick(grpc_pollset *pollset,
gpr_log(GPR_ERROR, "%s", tmp);
gpr_free(tmp);
}
if (specific_worker == NULL) {
if (gpr_tls_get(&g_current_thread_pollset) != (intptr_t)pollset) {
grpc_pollset_worker *root_worker = pollset->root_worker;
@ -1076,7 +1085,11 @@ static grpc_error *pollset_kick(grpc_pollset *pollset,
}
goto done;
}
} else if (specific_worker->kick_state == KICKED) {
GPR_UNREACHABLE_CODE(goto done);
}
if (specific_worker->kick_state == KICKED) {
if (GRPC_TRACER_ON(grpc_polling_trace)) {
gpr_log(GPR_ERROR, " .. specific worker already kicked");
}

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