ANDROID: binder: Switch binder_deferred_lock to a spinlock.

Avoid delays in binder transactions due to preemption of
binder_deferred_func() with binder_deferred_lock held.

Bug: 66914906
Test: boots; binder tests pass; trace analysis in bug
Change-Id: I1a89ba15b27e43552890292f135a5e2d969231e2
Signed-off-by: Corey Tabaka <eieio@google.com>

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index d726b03..870dbfc 100644 (file)
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -76,7 +76,7 @@
 #include "binder_trace.h"
 
 static HLIST_HEAD(binder_deferred_list);
-static DEFINE_MUTEX(binder_deferred_lock);
+static DEFINE_SPINLOCK(binder_deferred_lock);
 
 static HLIST_HEAD(binder_devices);
 static HLIST_HEAD(binder_procs);
@@ -5307,7 +5307,7 @@ static void binder_deferred_func(struct work_struct *work)
        int defer;
 
        do {
-               mutex_lock(&binder_deferred_lock);
+               spin_lock(&binder_deferred_lock);
                if (!hlist_empty(&binder_deferred_list)) {
                        proc = hlist_entry(binder_deferred_list.first,
                                        struct binder_proc, deferred_work_node);
@@ -5318,7 +5318,7 @@ static void binder_deferred_func(struct work_struct *work)
                        proc = NULL;
                        defer = 0;
                }
-               mutex_unlock(&binder_deferred_lock);
+               spin_unlock(&binder_deferred_lock);
 
                files = NULL;
                if (defer & BINDER_DEFERRED_PUT_FILES) {
@@ -5344,14 +5344,14 @@ static DECLARE_WORK(binder_deferred_work, binder_deferred_func);
 static void
 binder_defer_work(struct binder_proc *proc, enum binder_deferred_state defer)
 {
-       mutex_lock(&binder_deferred_lock);
+       spin_lock(&binder_deferred_lock);
        proc->deferred_work |= defer;
        if (hlist_unhashed(&proc->deferred_work_node)) {
                hlist_add_head(&proc->deferred_work_node,
                                &binder_deferred_list);
                queue_work(binder_deferred_workqueue, &binder_deferred_work);
        }
-       mutex_unlock(&binder_deferred_lock);
+       spin_unlock(&binder_deferred_lock);
 }
 
 static void print_binder_transaction_ilocked(struct seq_file *m,