libsuspend: always unblock early suspend

SurfaceFlinger and PowerManagerService manage their synchronization
without the help of early suspend, and SurfaceFlinger no longer unblocks
early suspend.  Add a new thread when early suspend is detected that will
immediately unblock early suspend.

Change-Id: I87ef4984a2ab34cbbb3af8b7762236b9a92dc2ea

libsuspend/autosuspend_earlysuspend.c

@@ -35,7 +35,56 @@
 static int sPowerStatefd;
 static const char *pwr_state_mem = "mem";
 static const char *pwr_state_on = "on";
+static pthread_t earlysuspend_thread;
 
+int wait_for_fb_wake(void)
+{
+    int err = 0;
+    char buf;
+    int fd = open(EARLYSUSPEND_WAIT_FOR_FB_WAKE, O_RDONLY, 0);
+    // if the file doesn't exist, the error will be caught in read() below
+    do {
+        err = read(fd, &buf, 1);
+    } while (err < 0 && errno == EINTR);
+    ALOGE_IF(err < 0,
+            "*** ANDROID_WAIT_FOR_FB_WAKE failed (%s)", strerror(errno));
+    close(fd);
+    return err < 0 ? err : 0;
+}
+
+static int wait_for_fb_sleep(void)
+{
+    int err = 0;
+    char buf;
+    int fd = open(EARLYSUSPEND_WAIT_FOR_FB_SLEEP, O_RDONLY, 0);
+    // if the file doesn't exist, the error will be caught in read() below
+    do {
+        err = read(fd, &buf, 1);
+    } while (err < 0 && errno == EINTR);
+    ALOGE_IF(err < 0,
+            "*** ANDROID_WAIT_FOR_FB_SLEEP failed (%s)", strerror(errno));
+    close(fd);
+    return err < 0 ? err : 0;
+}
+
+static void *earlysuspend_thread_func(void *arg)
+{
+    char buf[80];
+    char wakeup_count[20];
+    int wakeup_count_len;
+    int ret;
+
+    while (1) {
+        if (wait_for_fb_sleep()) {
+            ALOGE("Failed reading wait_for_fb_sleep, exiting earlysuspend thread\n");
+            return NULL;
+        }
+        if (wait_for_fb_wake()) {
+            ALOGE("Failed reading wait_for_fb_wake, exiting earlysuspend thread\n");
+            return NULL;
+        }
+    }
+}
 static int autosuspend_earlysuspend_enable(void)
 {
     char buf[80];
@@ -85,29 +134,56 @@ struct autosuspend_ops autosuspend_earlysuspend_ops = {
         .disable = autosuspend_earlysuspend_disable,
 };
 
-struct autosuspend_ops *autosuspend_earlysuspend_init(void)
+void start_earlysuspend_thread(void)
 {
     char buf[80];
     int ret;
 
     ret = access(EARLYSUSPEND_WAIT_FOR_FB_SLEEP, F_OK);
     if (ret < 0) {
-        return NULL;
+        return;
     }
 
     ret = access(EARLYSUSPEND_WAIT_FOR_FB_WAKE, F_OK);
     if (ret < 0) {
-        return NULL;
+        return;
     }
 
+    ALOGI("Starting early suspend unblocker thread\n");
+    ret = pthread_create(&earlysuspend_thread, NULL, earlysuspend_thread_func, NULL);
+    if (ret) {
+        strerror_r(ret, buf, sizeof(buf));
+        ALOGE("Error creating thread: %s\n", buf);
+    }
+}
+
+struct autosuspend_ops *autosuspend_earlysuspend_init(void)
+{
+    char buf[80];
+    int ret;
+
     sPowerStatefd = open(EARLYSUSPEND_SYS_POWER_STATE, O_RDWR);
 
     if (sPowerStatefd < 0) {
         strerror_r(errno, buf, sizeof(buf));
-        ALOGE("Error opening %s: %s\n", EARLYSUSPEND_SYS_POWER_STATE, buf);
+        ALOGW("Error opening %s: %s\n", EARLYSUSPEND_SYS_POWER_STATE, buf);
         return NULL;
     }
 
+    ret = write(sPowerStatefd, "on", 2);
+    if (ret < 0) {
+        strerror_r(errno, buf, sizeof(buf));
+        ALOGW("Error writing 'on' to %s: %s\n", EARLYSUSPEND_SYS_POWER_STATE, buf);
+        goto err_write;
+    }
+
     ALOGI("Selected early suspend\n");
+
+    start_earlysuspend_thread();
+
     return &autosuspend_earlysuspend_ops;
+
+err_write:
+    close(sPowerStatefd);
+    return NULL;
 }