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Commit be41ae56 authored by Josh Gao's avatar Josh Gao
Browse files

adb: fix flakiness in PTY shell protocol. 

When a subprocess closes its PTY slave, the master fd will report
POLLHUP when polled. This leads to us prematurely tearing everything
down, without reading out output that's been written to the PTY.

Resolve this by waiting until the fd no longer reports POLLIN.

Bug: http://b/156551485
Bug: http://b/156552734
Test: `adb shell 'X=0; while /data/nativetest64/adbd_test/adbd_test --gtest_filter="ShellServiceTest.*Pty*" >/dev/null 2>&1; do X=$((X+1)); echo $X; done'` for 1000 iterations (failed within 20, previously)
Test: test_device.py
Change-Id: Ie591e0cafb532cd6cebdf6f356dc967565b5a2d9
parent 1fbb1b87

adb/daemon/shell_service.cpp

+9 −3
Original line number Diff line number Diff line
@@ -646,15 +646,21 @@ unique_fd* Subprocess::PollLoop(SubprocessPollfds* pfds) { 
        }



        // After handling all of the events we've received, check to see if any fds have died.

        if (stdinout_pfd.revents & (POLLHUP | POLLRDHUP | POLLERR | POLLNVAL)) {

        auto poll_finished = [](int events) {

            // Don't return failure until we've read out all of the fd's incoming data.

            return (events & POLLIN) == 0 &&

                   (events & (POLLHUP | POLLRDHUP | POLLERR | POLLNVAL)) != 0;

        };



        if (poll_finished(stdinout_pfd.revents)) {

            return &stdinout_sfd_;

        }



        if (stderr_pfd.revents & (POLLHUP | POLLRDHUP | POLLERR | POLLNVAL)) {

        if (poll_finished(stderr_pfd.revents)) {

            return &stderr_sfd_;

        }



        if (protocol_pfd.revents & (POLLHUP | POLLRDHUP | POLLERR | POLLNVAL)) {

        if (poll_finished(protocol_pfd.revents)) {

            return &protocol_sfd_;

        }

    }  // while (!dead_sfd)