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-rw-r--r--src/core/client_config/lb_policies/pick_first.c62
1 files changed, 40 insertions, 22 deletions
diff --git a/src/core/client_config/lb_policies/pick_first.c b/src/core/client_config/lb_policies/pick_first.c
index 37de3e9f68..e6ddb1a11f 100644
--- a/src/core/client_config/lb_policies/pick_first.c
+++ b/src/core/client_config/lb_policies/pick_first.c
@@ -1,6 +1,6 @@
/*
*
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
@@ -55,12 +55,11 @@ typedef struct {
grpc_closure connectivity_changed;
+ /** the selected channel (a grpc_connected_subchannel) */
+ gpr_atm selected;
+
/** mutex protecting remaining members */
gpr_mu mu;
- /** the selected channel
- TODO(ctiller): this should be atomically set so we don't
- need to take a mutex in the common case */
- grpc_connected_subchannel *selected;
/** have we started picking? */
int started_picking;
/** are we shut down? */
@@ -76,15 +75,19 @@ typedef struct {
grpc_connectivity_state_tracker state_tracker;
} pick_first_lb_policy;
+#define GET_SELECTED(p) \
+ ((grpc_connected_subchannel *)gpr_atm_no_barrier_load(&(p)->selected))
+
void pf_destroy(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol) {
pick_first_lb_policy *p = (pick_first_lb_policy *)pol;
+ grpc_connected_subchannel *selected = GET_SELECTED(p);
size_t i;
GPR_ASSERT(p->pending_picks == NULL);
for (i = 0; i < p->num_subchannels; i++) {
GRPC_SUBCHANNEL_UNREF(exec_ctx, p->subchannels[i], "pick_first");
}
- if (p->selected) {
- GRPC_CONNECTED_SUBCHANNEL_UNREF(exec_ctx, p->selected, "picked_first");
+ if (selected != NULL) {
+ GRPC_CONNECTED_SUBCHANNEL_UNREF(exec_ctx, selected, "picked_first");
}
grpc_connectivity_state_destroy(exec_ctx, &p->state_tracker);
gpr_free(p->subchannels);
@@ -95,16 +98,18 @@ void pf_destroy(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol) {
void pf_shutdown(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol) {
pick_first_lb_policy *p = (pick_first_lb_policy *)pol;
pending_pick *pp;
+ grpc_connected_subchannel *selected;
gpr_mu_lock(&p->mu);
+ selected = GET_SELECTED(p);
p->shutdown = 1;
pp = p->pending_picks;
p->pending_picks = NULL;
grpc_connectivity_state_set(exec_ctx, &p->state_tracker,
GRPC_CHANNEL_FATAL_FAILURE, "shutdown");
/* cancel subscription */
- if (p->selected != NULL) {
+ if (selected != NULL) {
grpc_connected_subchannel_notify_on_state_change(
- exec_ctx, p->selected, NULL, NULL, &p->connectivity_changed);
+ exec_ctx, selected, NULL, NULL, &p->connectivity_changed);
} else {
grpc_subchannel_notify_on_state_change(
exec_ctx, p->subchannels[p->checking_subchannel], NULL, NULL,
@@ -171,10 +176,20 @@ int pf_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol, grpc_pollset *pollset,
grpc_connected_subchannel **target, grpc_closure *on_complete) {
pick_first_lb_policy *p = (pick_first_lb_policy *)pol;
pending_pick *pp;
+
+ /* Check atomically for a selected channel */
+ grpc_connected_subchannel *selected = GET_SELECTED(p);
+ if (selected != NULL) {
+ *target = selected;
+ return 1;
+ }
+
+ /* No subchannel selected yet, so acquire lock and then attempt again */
gpr_mu_lock(&p->mu);
- if (p->selected) {
+ selected = GET_SELECTED(p);
+ if (selected) {
gpr_mu_unlock(&p->mu);
- *target = p->selected;
+ *target = selected;
return 1;
} else {
if (!p->started_picking) {
@@ -219,14 +234,17 @@ static void pf_connectivity_changed(grpc_exec_ctx *exec_ctx, void *arg,
pick_first_lb_policy *p = arg;
grpc_subchannel *selected_subchannel;
pending_pick *pp;
+ grpc_connected_subchannel *selected;
gpr_mu_lock(&p->mu);
+ selected = GET_SELECTED(p);
+
if (p->shutdown) {
gpr_mu_unlock(&p->mu);
GRPC_LB_POLICY_WEAK_UNREF(exec_ctx, &p->base, "pick_first_connectivity");
return;
- } else if (p->selected != NULL) {
+ } else if (selected != NULL) {
if (p->checking_connectivity == GRPC_CHANNEL_TRANSIENT_FAILURE) {
/* if the selected channel goes bad, we're done */
p->checking_connectivity = GRPC_CHANNEL_FATAL_FAILURE;
@@ -235,7 +253,7 @@ static void pf_connectivity_changed(grpc_exec_ctx *exec_ctx, void *arg,
p->checking_connectivity, "selected_changed");
if (p->checking_connectivity != GRPC_CHANNEL_FATAL_FAILURE) {
grpc_connected_subchannel_notify_on_state_change(
- exec_ctx, p->selected, &p->base.interested_parties,
+ exec_ctx, selected, &p->base.interested_parties,
&p->checking_connectivity, &p->connectivity_changed);
} else {
GRPC_LB_POLICY_WEAK_UNREF(exec_ctx, &p->base, "pick_first_connectivity");
@@ -247,10 +265,11 @@ static void pf_connectivity_changed(grpc_exec_ctx *exec_ctx, void *arg,
grpc_connectivity_state_set(exec_ctx, &p->state_tracker,
GRPC_CHANNEL_READY, "connecting_ready");
selected_subchannel = p->subchannels[p->checking_subchannel];
- p->selected =
+ selected =
grpc_subchannel_get_connected_subchannel(selected_subchannel);
- GPR_ASSERT(p->selected);
- GRPC_CONNECTED_SUBCHANNEL_REF(p->selected, "picked_first");
+ GPR_ASSERT(selected != NULL);
+ gpr_atm_no_barrier_store(&p->selected, (gpr_atm)selected);
+ GRPC_CONNECTED_SUBCHANNEL_REF(selected, "picked_first");
/* drop the pick list: we are connected now */
GRPC_LB_POLICY_WEAK_REF(&p->base, "destroy_subchannels");
grpc_exec_ctx_enqueue(exec_ctx,
@@ -258,14 +277,14 @@ static void pf_connectivity_changed(grpc_exec_ctx *exec_ctx, void *arg,
/* update any calls that were waiting for a pick */
while ((pp = p->pending_picks)) {
p->pending_picks = pp->next;
- *pp->target = p->selected;
+ *pp->target = selected;
grpc_pollset_set_del_pollset(exec_ctx, &p->base.interested_parties,
pp->pollset);
grpc_exec_ctx_enqueue(exec_ctx, pp->on_complete, 1);
gpr_free(pp);
}
grpc_connected_subchannel_notify_on_state_change(
- exec_ctx, p->selected, &p->base.interested_parties,
+ exec_ctx, selected, &p->base.interested_parties,
&p->checking_connectivity, &p->connectivity_changed);
break;
case GRPC_CHANNEL_TRANSIENT_FAILURE:
@@ -351,13 +370,12 @@ void pf_notify_on_state_change(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol,
void pf_ping_one(grpc_exec_ctx *exec_ctx, grpc_lb_policy *pol,
grpc_closure *closure) {
pick_first_lb_policy *p = (pick_first_lb_policy *)pol;
- gpr_mu_lock(&p->mu);
- if (p->selected) {
- grpc_connected_subchannel_ping(exec_ctx, p->selected, closure);
+ grpc_connected_subchannel *selected = GET_SELECTED(p);
+ if (selected) {
+ grpc_connected_subchannel_ping(exec_ctx, selected, closure);
} else {
grpc_exec_ctx_enqueue(exec_ctx, closure, 0);
}
- gpr_mu_unlock(&p->mu);
}
static const grpc_lb_policy_vtable pick_first_lb_policy_vtable = {
generated by cgit v1.2.3 (git 2.39.1) at 2024-07-09 05:31:00 +0000