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Fix several races

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pull/10932/head
Craig Tiller 8 years ago
parent 2acab6e53a
commit ba550da853
1 changed files with 52 additions and 35 deletions
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  1. 87
      src/core/lib/iomgr/ev_epoll1_linux.c

87
src/core/lib/iomgr/ev_epoll1_linux.c
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@ -106,6 +106,8 @@ struct grpc_pollset_worker {
gpr_cv cv;
};
#define MAX_NEIGHBOURHOODS 1024
typedef struct pollset_neighbourhood {
gpr_mu mu;
grpc_pollset *active_root;
@ -121,6 +123,7 @@ struct grpc_pollset {
bool shutting_down; /* Is the pollset shutting down ? */
bool finish_shutdown_called; /* Is the 'finish_shutdown_locked()' called ? */
grpc_closure *shutdown_closure; /* Called after after shutdown is complete */
int begin_refs;
grpc_pollset *next;
grpc_pollset *prev;
@ -312,7 +315,6 @@ GPR_TLS_DECL(g_current_thread_pollset);
GPR_TLS_DECL(g_current_thread_worker);
static gpr_atm g_active_poller;
static pollset_neighbourhood *g_neighbourhoods;
static bool *g_neighbour_scan_state;
static size_t g_num_neighbourhoods;
/* Return true if first in list */
@ -352,6 +354,10 @@ static worker_remove_result worker_remove(grpc_pollset *pollset,
}
}
static size_t choose_neighbourhood(void) {
return (size_t)gpr_cpu_current_cpu() % g_num_neighbourhoods;
}
static grpc_error *pollset_global_init(void) {
gpr_tls_init(&g_current_thread_pollset);
gpr_tls_init(&g_current_thread_worker);
@ -364,11 +370,9 @@ static grpc_error *pollset_global_init(void) {
if (epoll_ctl(g_epfd, EPOLL_CTL_ADD, global_wakeup_fd.read_fd, &ev) != 0) {
return GRPC_OS_ERROR(errno, "epoll_ctl");
}
g_num_neighbourhoods = GPR_MAX(1, gpr_cpu_num_cores());
g_num_neighbourhoods = GPR_CLAMP(gpr_cpu_num_cores(), 1, MAX_NEIGHBOURHOODS);
g_neighbourhoods =
gpr_zalloc(sizeof(*g_neighbourhoods) * g_num_neighbourhoods);
g_neighbour_scan_state =
gpr_malloc(sizeof(*g_neighbour_scan_state) * g_num_neighbourhoods);
for (size_t i = 0; i < g_num_neighbourhoods; i++) {
gpr_mu_init(&g_neighbourhoods[i].mu);
}
@ -383,26 +387,27 @@ static void pollset_global_shutdown(void) {
gpr_mu_destroy(&g_neighbourhoods[i].mu);
}
gpr_free(g_neighbourhoods);
gpr_free(g_neighbour_scan_state);
}
static void pollset_init(grpc_pollset *pollset, gpr_mu **mu) {
gpr_mu_init(&pollset->mu);
*mu = &pollset->mu;
pollset->neighbourhood = &g_neighbourhoods[gpr_cpu_current_cpu()];
pollset->neighbourhood = &g_neighbourhoods[choose_neighbourhood()];
pollset->seen_inactive = true;
pollset->next = pollset->prev = pollset;
}
static void pollset_destroy(grpc_pollset *pollset) {
gpr_mu_lock(&pollset->neighbourhood->mu);
pollset->prev->next = pollset->next;
pollset->next->prev = pollset->prev;
if (pollset == pollset->neighbourhood->active_root) {
pollset->neighbourhood->active_root =
pollset->next == pollset ? NULL : pollset->next;
}
gpr_mu_unlock(&pollset->neighbourhood->mu);
if (!pollset->seen_inactive) {
gpr_mu_lock(&pollset->neighbourhood->mu);
pollset->prev->next = pollset->next;
pollset->next->prev = pollset->prev;
if (pollset == pollset->neighbourhood->active_root) {
pollset->neighbourhood->active_root =
pollset->next == pollset ? NULL : pollset->next;
}
gpr_mu_unlock(&pollset->neighbourhood->mu);
}
gpr_mu_destroy(&pollset->mu);
}
@ -428,7 +433,8 @@ static grpc_error *pollset_kick_all(grpc_pollset *pollset) {
static void pollset_maybe_finish_shutdown(grpc_exec_ctx *exec_ctx,
grpc_pollset *pollset) {
if (pollset->shutdown_closure != NULL && pollset->root_worker == NULL) {
if (pollset->shutdown_closure != NULL && pollset->root_worker == NULL &&
pollset->begin_refs == 0) {
grpc_closure_sched(exec_ctx, pollset->shutdown_closure, GRPC_ERROR_NONE);
pollset->shutdown_closure = NULL;
}
@ -532,14 +538,16 @@ static bool begin_worker(grpc_pollset *pollset, grpc_pollset_worker *worker,
if (worker_hdl != NULL) *worker_hdl = worker;
worker->initialized_cv = false;
worker->kick_state = UNKICKED;
pollset->begin_refs++;
if (pollset->seen_inactive) {
// pollset has been observed to be inactive, we need to move back to the
// active list
pollset_neighbourhood *neighbourhood = pollset->neighbourhood = &g_neighbourhoods[gpr_cpu_current_cpu()];
pollset_neighbourhood *neighbourhood = pollset->neighbourhood =
&g_neighbourhoods[choose_neighbourhood()];
gpr_mu_unlock(&pollset->mu);
// pollset unlocked: state may change (even worker->kick_state)
retry_lock_neighbourhood:
// pollset unlocked: state may change (even worker->kick_state)
retry_lock_neighbourhood:
gpr_mu_lock(&neighbourhood->mu);
gpr_mu_lock(&pollset->mu);
if (pollset->seen_inactive) {
@ -564,16 +572,18 @@ retry_lock_neighbourhood:
gpr_mu_unlock(&neighbourhood->mu);
}
worker_insert(pollset, worker);
pollset->begin_refs--;
if (worker->kick_state == UNKICKED) {
GPR_ASSERT(gpr_atm_no_barrier_load(&g_active_poller) != (gpr_atm)worker);
worker->initialized_cv = true;
gpr_cv_init(&worker->cv);
do {
while (worker->kick_state == UNKICKED &&
pollset->shutdown_closure == NULL) {
if (gpr_cv_wait(&worker->cv, &pollset->mu, deadline) &&
worker->kick_state == UNKICKED) {
worker->kick_state = KICKED;
}
} while (worker->kick_state == UNKICKED);
}
*now = gpr_now(now->clock_type);
}
@ -594,17 +604,24 @@ static bool check_neighbourhood_for_available_poller(
grpc_pollset_worker *inspect_worker = inspect->root_worker;
if (inspect_worker != NULL) {
do {
if (inspect_worker->kick_state == UNKICKED) {
if (gpr_atm_no_barrier_cas(&g_active_poller, 0,
(gpr_atm)inspect_worker)) {
inspect_worker->kick_state = DESIGNATED_POLLER;
if (inspect_worker->initialized_cv) {
gpr_cv_signal(&inspect_worker->cv);
switch (inspect_worker->kick_state) {
case UNKICKED:
if (gpr_atm_no_barrier_cas(&g_active_poller, 0,
(gpr_atm)inspect_worker)) {
inspect_worker->kick_state = DESIGNATED_POLLER;
if (inspect_worker->initialized_cv) {
gpr_cv_signal(&inspect_worker->cv);
}
}
}
// even if we didn't win the cas, there's a worker, we can stop
found_worker = true;
break;
// even if we didn't win the cas, there's a worker, we can stop
found_worker = true;
break;
case KICKED:
break;
case DESIGNATED_POLLER:
found_worker = true; // ok, so someone else found the worker, but
// we'll accept that
break;
}
inspect_worker = inspect_worker->next;
} while (inspect_worker != inspect->root_worker);
@ -649,6 +666,7 @@ static void end_worker(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
size_t poller_neighbourhood_idx =
(size_t)(pollset->neighbourhood - g_neighbourhoods);
bool found_worker = false;
bool scan_state[MAX_NEIGHBOURHOODS];
for (size_t i = 0; !found_worker && i < g_num_neighbourhoods; i++) {
pollset_neighbourhood *neighbourhood =
&g_neighbourhoods[(poller_neighbourhood_idx + i) %
@ -657,19 +675,18 @@ static void end_worker(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
found_worker =
check_neighbourhood_for_available_poller(neighbourhood);
gpr_mu_unlock(&neighbourhood->mu);
g_neighbour_scan_state[i] = true;
scan_state[i] = true;
} else {
g_neighbour_scan_state[i] = false;
scan_state[i] = false;
}
}
for (size_t i = 0; !found_worker && i < g_num_neighbourhoods; i++) {
if (g_neighbour_scan_state[i]) continue;
if (scan_state[i]) continue;
pollset_neighbourhood *neighbourhood =
&g_neighbourhoods[(poller_neighbourhood_idx + i) %
g_num_neighbourhoods];
gpr_mu_lock(&neighbourhood->mu);
found_worker =
check_neighbourhood_for_available_poller(neighbourhood);
found_worker = check_neighbourhood_for_available_poller(neighbourhood);
gpr_mu_unlock(&neighbourhood->mu);
}
grpc_exec_ctx_flush(exec_ctx);

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