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binder: use atomics for weak/strong counters

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To avoid needing to lock when changing refcounts
change to atomics

Bug: 33250092 32225111
Change-Id: I03b8b5b2d15da0750452152b8cf9ae45c410546e
Signed-off-by: Todd Kjos <tkjos@google.com>
This commit is contained in:
Badhri Jagan Sridharan
2016-10-12 15:58:47 -07:00
committed by Thierry Strudel
parent c363358e81
commit c3eef445f4
1 changed files with 43 additions and 37 deletions
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80
drivers/android/binder.c
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@@ -295,8 +295,8 @@ struct binder_ref {
struct binder_proc *proc;
struct binder_node *node;
uint32_t desc;
int strong;
int weak;
atomic_t strong;
atomic_t weak;
struct binder_ref_death *death;
};
@@ -611,7 +611,7 @@ static struct binder_ref *binder_get_ref(struct binder_proc *proc,
n = n->rb_left;
} else if (desc > ref->desc) {
n = n->rb_right;
} else if (need_strong_ref && !ref->strong) {
} else if (need_strong_ref && !atomic_read(&ref->strong)) {
binder_user_error("tried to use weak ref as strong ref\n");
return NULL;
} else {
@@ -648,6 +648,8 @@ static struct binder_ref *binder_get_ref_for_node(struct binder_proc *proc,
new_ref->debug_id = ++binder_last_id;
new_ref->proc = proc;
new_ref->node = node;
atomic_set(&new_ref->strong, 0);
atomic_set(&new_ref->weak, 0);
rb_link_node(&new_ref->rb_node_node, parent, p);
rb_insert_color(&new_ref->rb_node_node, &proc->refs_by_node);
@@ -697,7 +699,7 @@ static void binder_delete_ref(struct binder_ref *ref)
rb_erase(&ref->rb_node_desc, &ref->proc->refs_by_desc);
rb_erase(&ref->rb_node_node, &ref->proc->refs_by_node);
if (ref->strong)
if (atomic_read(&ref->strong))
binder_dec_node(ref->node, 1, 1);
hlist_del(&ref->node_entry);
binder_dec_node(ref->node, 0, 1);
@@ -716,54 +718,52 @@ static void binder_delete_ref(struct binder_ref *ref)
static int binder_inc_ref(struct binder_ref *ref, int strong,
struct list_head *target_list)
{
int ret;
int ret = 0;
if (strong) {
if (ref->strong == 0) {
ret = binder_inc_node(ref->node, 1, 1, target_list);
if (ret)
return ret;
/* atomic_inc_return does not require explicit barrier */
if ((strong && atomic_inc_return(&ref->strong) == 1) ||
(!strong && atomic_inc_return(&ref->weak) == 1)) {
ret = binder_inc_node(ref->node, strong, 1, target_list);
if (ret) {
atomic_dec(strong ? &ref->strong : &ref->weak);
smp_mb__after_atomic();
}
ref->strong++;
} else {
if (ref->weak == 0) {
ret = binder_inc_node(ref->node, 0, 1, target_list);
if (ret)
return ret;
}
ref->weak++;
}
return 0;
}
return ret;
}
static int binder_dec_ref(struct binder_ref *ref, int strong)
{
if (strong) {
if (ref->strong == 0) {
/* atomic_dec_if_positive does not require explicit barrier */
int newval = atomic_dec_if_positive(&ref->strong);
if (newval < 0) {
binder_user_error("%d invalid dec strong, ref %d desc %d s %d w %d\n",
ref->proc->pid, ref->debug_id,
ref->desc, ref->strong, ref->weak);
ref->desc, atomic_read(&ref->strong),
atomic_read(&ref->weak));
return -EINVAL;
}
ref->strong--;
if (ref->strong == 0) {
int ret;
ret = binder_dec_node(ref->node, strong, 1);
if (newval == 0) {
int ret = binder_dec_node(ref->node, strong, 1);
if (ret)
return ret;
}
} else {
if (ref->weak == 0) {
int newval = atomic_dec_if_positive(&ref->weak);
if (newval < 0) {
binder_user_error("%d invalid dec weak, ref %d desc %d s %d w %d\n",
ref->proc->pid, ref->debug_id,
ref->desc, ref->strong, ref->weak);
ref->desc, atomic_read(&ref->strong),
atomic_read(&ref->weak));
return -EINVAL;
}
ref->weak--;
}
if (ref->strong == 0 && ref->weak == 0)
if (atomic_read(&ref->strong) == 0 && atomic_read(&ref->weak) == 0)
binder_delete_ref(ref);
return 0;
}
@@ -1889,8 +1889,11 @@ static int binder_thread_write(struct binder_proc *proc,
}
binder_debug(BINDER_DEBUG_USER_REFS,
"%d:%d %s ref %d desc %d s %d w %d for node %d\n",
proc->pid, thread->pid, debug_string, ref->debug_id,
ref->desc, ref->strong, ref->weak, ref->node->debug_id);
proc->pid, thread->pid, debug_string,
ref->debug_id, ref->desc,
atomic_read(&ref->strong),
atomic_read(&ref->weak),
ref->node->debug_id);
break;
}
case BC_INCREFS_DONE:
@@ -2093,7 +2096,9 @@ static int binder_thread_write(struct binder_proc *proc,
"BC_REQUEST_DEATH_NOTIFICATION" :
"BC_CLEAR_DEATH_NOTIFICATION",
(u64)cookie, ref->debug_id, ref->desc,
ref->strong, ref->weak, ref->node->debug_id);
atomic_read(&ref->strong),
atomic_read(&ref->weak),
ref->node->debug_id);
if (cmd == BC_REQUEST_DEATH_NOTIFICATION) {
if (ref->death) {
@@ -3357,7 +3362,8 @@ static void print_binder_ref(struct seq_file *m, struct binder_ref *ref)
{
seq_printf(m, " ref %d: desc %d %snode %d s %d w %d d %p\n",
ref->debug_id, ref->desc, ref->node->proc ? "" : "dead ",
ref->node->debug_id, ref->strong, ref->weak, ref->death);
ref->node->debug_id, atomic_read(&ref->strong),
atomic_read(&ref->weak), ref->death);
}
static void print_binder_proc(struct seq_file *m,
@@ -3526,8 +3532,8 @@ static void print_binder_proc_stats(struct seq_file *m,
struct binder_ref *ref = rb_entry(n, struct binder_ref,
rb_node_desc);
count++;
strong += ref->strong;
weak += ref->weak;
strong += atomic_read(&ref->strong);
weak += atomic_read(&ref->weak);
}
seq_printf(m, " refs: %d s %d w %d\n", count, strong, weak);