adb: detect when the client disconnects in wait-for-device.

Avoid leaking a thread and its associated resources when a user cancels
wait-for-device.

Bug: http://b/26966721
Bug: https://code.google.com/p/android/issues/detail?id=199088
Change-Id: Idac80a24e9739ddd24e500fe14826a78f350c018

adb/services.cpp

@@ -49,6 +49,7 @@
 #include "remount_service.h"
 #include "services.h"
 #include "shell_service.h"
+#include "sysdeps.h"
 #include "transport.h"
 
 struct stinfo {
@@ -369,12 +370,21 @@ static void wait_for_state(int fd, void* data) {
         std::string error = "unknown error";
         const char* serial = sinfo->serial.length() ? sinfo->serial.c_str() : NULL;
         atransport* t = acquire_one_transport(sinfo->transport_type, serial, &is_ambiguous, &error);
-
         if (t != nullptr && t->connection_state == sinfo->state) {
             SendOkay(fd);
             break;
         } else if (!is_ambiguous) {
-            adb_sleep_ms(1000);
+            adb_pollfd pfd = {.fd = fd, .events = POLLIN };
+            int rc = adb_poll(&pfd, 1, 1000);
+            if (rc < 0) {
+                SendFail(fd, error);
+                break;
+            } else if (rc > 0 && (pfd.revents & POLLHUP) != 0) {
+                // The other end of the socket is closed, probably because the other side was
+                // terminated, bail out.
+                break;
+            }
+
             // Try again...
         } else {
             SendFail(fd, error);

adb/sysdeps_test.cpp

@@ -112,8 +112,12 @@ class sysdeps_poll : public ::testing::Test {
     }
 
     void TearDown() override {
-        ASSERT_EQ(0, adb_close(fds[0]));
-        ASSERT_EQ(0, adb_close(fds[1]));
+        if (fds[0] >= 0) {
+            ASSERT_EQ(0, adb_close(fds[0]));
+        }
+        if (fds[1] >= 0) {
+            ASSERT_EQ(0, adb_close(fds[1]));
+        }
     }
 };
 
@@ -190,3 +194,20 @@ TEST_F(sysdeps_poll, duplicate_fd) {
     EXPECT_EQ(POLLRDNORM, pfd[0].revents);
     EXPECT_EQ(POLLRDNORM, pfd[1].revents);
 }
+
+TEST_F(sysdeps_poll, disconnect) {
+    adb_pollfd pfd;
+    pfd.fd = fds[0];
+    pfd.events = POLLIN;
+
+    EXPECT_EQ(0, adb_poll(&pfd, 1, 0));
+    EXPECT_EQ(0, pfd.revents);
+
+    EXPECT_EQ(0, adb_close(fds[1]));
+    fds[1] = -1;
+
+    EXPECT_EQ(1, adb_poll(&pfd, 1, 100));
+
+    // Linux returns POLLIN | POLLHUP, Windows returns just POLLHUP.
+    EXPECT_EQ(POLLHUP, pfd.revents & POLLHUP);
+}