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binder: don't modify thread->looper from other threads

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The looper member of struct binder_thread is a bitmask
of control bits. All of the existing bits are modified
by the affected thread except for BINDER_LOOPER_STATE_NEED_RETURN
which can be modified in binder_deferred_flush() by
another thread.

To avoid adding a spinlock around all read-mod-writes to
modify a bit, the BINDER_LOOPER_STATE_NEED_RETURN flag
is replaced by a separate field in struct binder_thread.

Bug: 33250092 32225111
Change-Id: Ia4cefbdbd683c6cb17c323ba7d278de5f2ca0745
Signed-off-by: Todd Kjos <tkjos@google.com>
This commit is contained in:
Todd Kjos
2017-01-06 14:19:25 -08:00
committed by Thierry Strudel
parent e3ede3cdf6
commit c9c6590330
1 changed files with 11 additions and 11 deletions
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22
drivers/android/binder.c
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@@ -395,7 +395,6 @@ enum {
BINDER_LOOPER_STATE_EXITED = 0x04,
BINDER_LOOPER_STATE_INVALID = 0x08,
BINDER_LOOPER_STATE_WAITING = 0x10,
BINDER_LOOPER_STATE_NEED_RETURN = 0x20
};
struct binder_thread {
@@ -407,7 +406,8 @@ struct binder_thread {
struct binder_seq_node active_node;
int pid;
int looper;
int looper; /* only modified by this thread */
bool looper_need_return; /* can be written by other thread */
struct binder_transaction *transaction_stack;
struct binder_worklist todo;
uint32_t return_error; /* Write failed, return error code in read buf */
@@ -2664,14 +2664,14 @@ static inline int binder_has_proc_work(struct binder_proc *proc,
struct binder_thread *thread)
{
return !binder_worklist_empty(&proc->todo) ||
(thread->looper & BINDER_LOOPER_STATE_NEED_RETURN);
READ_ONCE(thread->looper_need_return);
}
static inline int binder_has_thread_work(struct binder_thread *thread)
{
return !binder_worklist_empty(&thread->todo) ||
thread->return_error != BR_OK ||
(thread->looper & BINDER_LOOPER_STATE_NEED_RETURN);
READ_ONCE(thread->looper_need_return);
}
static int binder_thread_read(struct binder_proc *proc,
@@ -2802,10 +2802,8 @@ retry:
binder_proc_unlock(thread->proc, __LINE__);
/* no data added */
if (ptr - buffer == 4 &&
!(thread->looper &
BINDER_LOOPER_STATE_NEED_RETURN)) {
!READ_ONCE(thread->looper_need_return))
goto retry;
}
break;
}
}
@@ -3253,7 +3251,7 @@ static struct binder_thread *binder_get_thread(struct binder_proc *proc)
new_thread->pid = current->pid;
init_waitqueue_head(&new_thread->wait);
binder_init_worklist(&new_thread->todo);
new_thread->looper |= BINDER_LOOPER_STATE_NEED_RETURN;
WRITE_ONCE(new_thread->looper_need_return, true);
new_thread->return_error = BR_OK;
new_thread->return_error2 = BR_OK;
INIT_LIST_HEAD(&new_thread->active_node.list_node);
@@ -3623,7 +3621,7 @@ static long binder_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
err:
if (thread) {
binder_proc_lock(thread->proc, __LINE__);
thread->looper &= ~BINDER_LOOPER_STATE_NEED_RETURN;
WRITE_ONCE(thread->looper_need_return, false);
binder_proc_unlock(thread->proc, __LINE__);
zombie_cleanup_check(proc);
binder_put_thread(thread);
@@ -3812,7 +3810,7 @@ static void binder_deferred_flush(struct binder_proc *proc)
struct binder_thread *thread;
thread = rb_entry(n, struct binder_thread, rb_node);
thread->looper |= BINDER_LOOPER_STATE_NEED_RETURN;
WRITE_ONCE(thread->looper_need_return, true);
if (thread->looper & BINDER_LOOPER_STATE_WAITING) {
if (i < count)
waits[i] = &thread->wait;
@@ -4252,7 +4250,9 @@ static void _print_binder_thread(struct seq_file *m,
BUG_ON(!spin_is_locked(&thread->proc->proc_lock));
seq_printf(m, " thread %d: l %02x\n", thread->pid, thread->looper);
seq_printf(m, " thread %d: l %02x need_return %d\n",
thread->pid, thread->looper,
READ_ONCE(thread->looper_need_return));
header_pos = m->count;
t = thread->transaction_stack;
while (t) {