Change UHID socket to be non-blocking

On some platforms, the logs indicate that the BTU task is stalled by
UHID driver when writing the HID descriptor to the kernel. This patch
converts the UHID socket to non-blocking to avoid stalling the main
BTU task.

Bug: 23978964
Change-Id: I5a7a3e106fb2c967d68f077faedcd4fe62bbd912

3 files changed, 46 insertions, 14 deletions

diff --git a/btif/co/bta_hh_co.c b/btif/co/bta_hh_co.c
index 063326a28..0b090d5d6 100644
--- a/btif/co/bta_hh_co.c
+++ b/btif/co/bta_hh_co.c
@@ -43,11 +43,23 @@ const char *dev_path = "/dev/uhid";
 static tBTA_HH_RPT_CACHE_ENTRY sReportCache[BTA_HH_NV_LOAD_MAX];
 #endif
 
+void uhid_set_non_blocking(int fd)
+{
+    int opts = fcntl(fd, F_GETFL);
+    if (opts < 0)
+        APPL_TRACE_ERROR("%s() Getting flags failed (%s)", __func__, strerror(errno));
+
+    opts |= O_NONBLOCK;
+
+    if (fcntl(fd, F_SETFL, opts) < 0)
+        APPL_TRACE_EVENT("%s() Setting non-blocking flag failed (%s)", __func__, strerror(errno));
+}
+
 /*Internal function to perform UHID write and error checking*/
 static int uhid_write(int fd, const struct uhid_event *ev)
 {
-    ssize_t ret;
-    ret = write(fd, ev, sizeof(*ev));
+    ssize_t ret = write(fd, ev, sizeof(*ev));
+
     if (ret < 0){
         int rtn = -errno;
         APPL_TRACE_ERROR("%s: Cannot write to uhid:%s",
@@ -57,9 +69,9 @@ static int uhid_write(int fd, const struct uhid_event *ev)
         APPL_TRACE_ERROR("%s: Wrong size written to uhid: %zd != %zu",
                          __FUNCTION__, ret, sizeof(*ev));
         return -EFAULT;
-    } else {
-        return 0;
     }
+
+    return 0;
 }
 
 /* Internal function to parse the events received from UHID driver*/
@@ -82,24 +94,31 @@ static int uhid_event(btif_hh_device_t *p_dev)
         APPL_TRACE_ERROR("%s: Cannot read uhid-cdev: %s", __FUNCTION__,
                                                 strerror(errno));
         return -errno;
-    } else if (ret < (ssize_t)sizeof(ev.type)) {
-        APPL_TRACE_ERROR("%s: Invalid size read from uhid-dev: %zd < %zu",
+    } else if ((ev.type == UHID_OUTPUT) || (ev.type==UHID_OUTPUT_EV)) {
+        // Only these two types havae payload,
+        // ensure we read full event descriptor
+        if (ret < (ssize_t)sizeof(ev)) {
+            APPL_TRACE_ERROR("%s: Invalid size read from uhid-dev: %ld != %lu",
                          __FUNCTION__, ret, sizeof(ev.type));
-        return -EFAULT;
+            return -EFAULT;
+        }
     }
 
     switch (ev.type) {
     case UHID_START:
         APPL_TRACE_DEBUG("UHID_START from uhid-dev\n");
+        p_dev->ready_for_data = TRUE;
         break;
     case UHID_STOP:
         APPL_TRACE_DEBUG("UHID_STOP from uhid-dev\n");
+        p_dev->ready_for_data = FALSE;
         break;
     case UHID_OPEN:
         APPL_TRACE_DEBUG("UHID_OPEN from uhid-dev\n");
         break;
     case UHID_CLOSE:
         APPL_TRACE_DEBUG("UHID_CLOSE from uhid-dev\n");
+        p_dev->ready_for_data = FALSE;
         break;
     case UHID_OUTPUT:
         if (ret < (ssize_t)(sizeof(ev.type) + sizeof(ev.u.output))) {
@@ -175,14 +194,17 @@ static inline pthread_t create_thread(void *(*start_routine)(void *), void * arg
 *******************************************************************************/
 static void *btif_hh_poll_event_thread(void *arg)
 {
-
     btif_hh_device_t *p_dev = arg;
     APPL_TRACE_DEBUG("%s: Thread created fd = %d", __FUNCTION__, p_dev->fd);
     struct pollfd pfds[1];
     int ret;
+
     pfds[0].fd = p_dev->fd;
     pfds[0].events = POLLIN;
 
+    // Set the uhid fd as non-blocking to ensure we never block the BTU thread
+    uhid_set_non_blocking(p_dev->fd);
+
     while(p_dev->hh_keep_polling){
         ret = poll(pfds, 1, 50);
         if (ret < 0) {
@@ -224,7 +246,8 @@ void bta_hh_co_destroy(int fd)
 
 int bta_hh_co_write(int fd, UINT8* rpt, UINT16 len)
 {
-    APPL_TRACE_DEBUG("bta_hh_co_data: UHID write");
+    APPL_TRACE_DEBUG("%s: UHID write %d", __func__, len);
+
     struct uhid_event ev;
     memset(&ev, 0, sizeof(ev));
     ev.type = UHID_INPUT;
@@ -235,6 +258,7 @@ int bta_hh_co_write(int fd, UINT8* rpt, UINT16 len)
         return -1;
     }
     memcpy(ev.u.input.data, rpt, len);
+
     return uhid_write(fd, &ev);
 
 }
@@ -280,9 +304,11 @@ void bta_hh_co_open(UINT8 dev_handle, UINT8 sub_class, tBTA_HH_ATTR_MASK attr_ma
                 if (p_dev->fd < 0){
                     APPL_TRACE_ERROR("%s: Error: failed to open uhid, err:%s",
                                                                     __FUNCTION__,strerror(errno));
+                    return;
                 }else
                     APPL_TRACE_DEBUG("%s: uhid fd = %d", __FUNCTION__, p_dev->fd);
             }
+
             p_dev->hh_keep_polling = 1;
             p_dev->hh_poll_thread_id = create_thread(btif_hh_poll_event_thread, p_dev);
             break;
@@ -307,6 +333,7 @@ void bta_hh_co_open(UINT8 dev_handle, UINT8 sub_class, tBTA_HH_ATTR_MASK attr_ma
                 if (p_dev->fd < 0){
                     APPL_TRACE_ERROR("%s: Error: failed to open uhid, err:%s",
                                                                     __FUNCTION__,strerror(errno));
+                    return;
                 }else{
                     APPL_TRACE_DEBUG("%s: uhid fd = %d", __FUNCTION__, p_dev->fd);
                     p_dev->hh_keep_polling = 1;
@@ -397,11 +424,13 @@ void bta_hh_co_data(UINT8 dev_handle, UINT8 *p_rpt, UINT16 len, tBTA_HH_PROTO_MO
         APPL_TRACE_WARNING("%s: Error: unknown HID device handle %d", __FUNCTION__, dev_handle);
         return;
     }
-    // Send the HID report to the kernel.
-    if (p_dev->fd >= 0) {
+
+    // Send the HID data to the kernel.
+    if ((p_dev->fd >= 0) && p_dev->ready_for_data) {
         bta_hh_co_write(p_dev->fd, p_rpt, len);
     }else {
-        APPL_TRACE_WARNING("%s: Error: fd = %d, len = %d", __FUNCTION__, p_dev->fd, len);
+        APPL_TRACE_WARNING("%s: Error: fd = %d, ready %d, len = %d", __FUNCTION__, p_dev->fd, 
+                            p_dev->ready_for_data, len);
     }
 }
 
@@ -437,7 +466,7 @@ void bta_hh_co_send_hid_info(btif_hh_device_t *p_dev, char *dev_name, UINT16 ven
                                                                     vendor_id, product_id,
                                                                     version, ctry_code);
 
-//Create and send hid descriptor to kernel
+    //Create and send hid descriptor to kernel
     memset(&ev, 0, sizeof(ev));
     ev.type = UHID_CREATE;
     strncpy((char*)ev.u.create.name, dev_name, sizeof(ev.u.create.name) - 1);
@@ -455,7 +484,7 @@ void bta_hh_co_send_hid_info(btif_hh_device_t *p_dev, char *dev_name, UINT16 ven
     ev.u.create.country = ctry_code;
     result = uhid_write(p_dev->fd, &ev);
 
-    APPL_TRACE_WARNING("%s: fd = %d, dscp_len = %d, result = %d", __FUNCTION__,
+    APPL_TRACE_WARNING("%s: wrote descriptor to fd = %d, dscp_len = %d, result = %d", __FUNCTION__,
                                                                     p_dev->fd, dscp_len, result);
 
     if (result) {
diff --git a/btif/include/btif_hh.h b/btif/include/btif_hh.h
index dc34d653c..1088c53bf 100644
--- a/btif/include/btif_hh.h
+++ b/btif/include/btif_hh.h
@@ -64,6 +64,7 @@ typedef struct
     UINT8                         sub_class;
     UINT8                         app_id;
     int                           fd;
+    BOOLEAN                       ready_for_data;
     pthread_t                     hh_poll_thread_id;
     UINT8                         hh_keep_polling;
     BOOLEAN                       vup_timer_active;
diff --git a/btif/src/btif_hh.c b/btif/src/btif_hh.c
index f668143ab..52296de9c 100644
--- a/btif/src/btif_hh.c
+++ b/btif/src/btif_hh.c
@@ -518,6 +518,8 @@ void btif_hh_remove_device(bt_bdaddr_t bd_addr)
 
     p_dev->dev_status = BTHH_CONN_STATE_UNKNOWN;
     p_dev->dev_handle = BTA_HH_INVALID_HANDLE;
+    p_dev->ready_for_data = FALSE;
+
     if (btif_hh_cb.device_num > 0) {
         btif_hh_cb.device_num--;
     }