Merge lp:~aacid/mir/eintr_dispatch_loop into lp:mir

[Albert Astals Cid]

Do not throw exception on EINTR when poll()ing

[Alberto Aguirre (albaguirre)]

Oh yeah we used to have this with the single thread dispatcher.

And we have a test for this but it's disabled.

review: Approve

[PS Jenkins bot (ps-jenkins)]

FAILED: Continuous integration, rev:3104
http://jenkins.qa.ubuntu.com/job/mir-ci/5578/
Executed test runs:
    SUCCESS: http://jenkins.qa.ubuntu.com/job/mir-android-vivid-i386-build/4907
    FAILURE: http://jenkins.qa.ubuntu.com/job/mir-clang-vivid-amd64-build/3814/console
    FAILURE: http://jenkins.qa.ubuntu.com/job/mir-mediumtests-vivid-touch/4850/console
    FAILURE: http://jenkins.qa.ubuntu.com/job/mir-mediumtests-wily-touch/807/console
    SUCCESS: http://jenkins.qa.ubuntu.com/job/mir-wily-amd64-ci/1732
        deb: http://jenkins.qa.ubuntu.com/job/mir-wily-amd64-ci/1732/artifact/work/output/*zip*/output.zip
    None: http://jenkins.qa.ubuntu.com/job/mir-wily-i386-ci/807/console
    SUCCESS: http://jenkins.qa.ubuntu.com/job/mir-mediumtests-builder-vivid-armhf/4851
        deb: http://jenkins.qa.ubuntu.com/job/mir-mediumtests-builder-vivid-armhf/4851/artifact/work/output/*zip*/output.zip
    FAILURE: http://jenkins.qa.ubuntu.com/job/mir-mediumtests-runner-touch/7430/console
    SUCCESS: http://s-jenkins.ubuntu-ci:8080/job/touch-flash-device/25229
    FAILURE: http://jenkins.qa.ubuntu.com/job/mir-mediumtests-builder-wily-armhf/808/console

Click here to trigger a rebuild:
http://s-jenkins.ubuntu-ci:8080/job/mir-ci/5578/rebuild

review: Needs Fixing (continuous-integration)

[Kevin DuBois (kdub)]

> Oh yeah we used to have this with the single thread dispatcher.
>
> And we have a test for this but it's disabled.

is there a bug about the disabled test? lgtm otherwise

review: Approve

[Chris Halse Rogers (raof)]

Wait - how did you manage to get an EINTR in the dispatch thread?

We *should* be blocking all signals to that thread. SIGSTOP and SIGKILL can't be blocked, but SIGKILL will immediately end the process so that's not the problem.

We *do* send SIGSTOP to various things, but poll should *not* return EINTR after a SIGSTOP/SIGCONT pair. epoll() (erroneously) does, but poll() is not documented as suffering from that bug.

Oooh! Unless something is registering a SIGCONT handler. Stupid signal behaviour!

Quoth the signal (7) manpage:
   Interruption of system calls and library functions by stop signals
       On Linux, even in the absence of signal handlers, certain blocking interfaces can fail with the
       error EINTR after the process is stopped by one of the stop signals and then resumed via SIG‐
       CONT. This behavior is not sanctioned by POSIX.1, and doesn't occur on other systems.

       The Linux interfaces that display this behavior are:

           * "Input" socket interfaces, when a timeout (SO_RCVTIMEO) has been set on the socket using
             setsockopt(2): accept(2), recv(2), recvfrom(2), recvmmsg(2) (also with a non-NULL timeout
             argument), and recvmsg(2).

           * "Output" socket interfaces, when a timeout (SO_RCVTIMEO) has been set on the socket using
             setsockopt(2): connect(2), send(2), sendto(2), and sendmsg(2), if a send timeout (SO_SND‐
             TIMEO) has been set.

           * epoll_wait(2), epoll_pwait(2).

           * semop(2), semtimedop(2).

           * sigtimedwait(2), sigwaitinfo(2).

           * read(2) from an inotify(7) file descriptor.

           * Linux 2.6.21 and earlier: futex(2) FUTEX_WAIT, sem_timedwait(3), sem_wait(3).

           * Linux 2.6.8 and earlier: msgrcv(2), msgsnd(2).

           * Linux 2.4 and earlier: nanosleep(2).

review: Approve

[Alan Griffiths (alan-griffiths)]

Thanks Chris, I did wonder.

review: Approve

[PS Jenkins bot (ps-jenkins)]

FAILED: Autolanding.
More details in the following jenkins job:
http://jenkins.qa.ubuntu.com/job/mir-autolanding/2141/
Executed test runs:
    SUCCESS: http://jenkins.qa.ubuntu.com/job/mir-android-vivid-i386-build/4942
    FAILURE: http://jenkins.qa.ubuntu.com/job/mir-clang-vivid-amd64-build/3848/console
    SUCCESS: http://jenkins.qa.ubuntu.com/job/mir-mediumtests-vivid-touch/4888
    FAILURE: http://jenkins.qa.ubuntu.com/job/mir-mediumtests-wily-touch/844/console
    SUCCESS: http://jenkins.qa.ubuntu.com/job/mir-wily-amd64-autolanding/694
        deb: http://jenkins.qa.ubuntu.com/job/mir-wily-amd64-autolanding/694/artifact/work/output/*zip*/output.zip
    SUCCESS: http://jenkins.qa.ubuntu.com/job/mir-wily-i386-ci/842
        deb: http://jenkins.qa.ubuntu.com/job/mir-wily-i386-ci/842/artifact/work/output/*zip*/output.zip
    SUCCESS: http://jenkins.qa.ubuntu.com/job/mir-mediumtests-builder-vivid-armhf/4888
        deb: http://jenkins.qa.ubuntu.com/job/mir-mediumtests-builder-vivid-armhf/4888/artifact/work/output/*zip*/output.zip
    SUCCESS: http://jenkins.qa.ubuntu.com/job/mir-mediumtests-runner-touch/7454
    SUCCESS: http://s-jenkins.ubuntu-ci:8080/job/touch-flash-device/25311
    FAILURE: http://jenkins.qa.ubuntu.com/job/mir-mediumtests-builder-wily-armhf/845/console

review: Needs Fixing (continuous-integration)

[PS Jenkins bot (ps-jenkins)]

FAILED: Autolanding.
More details in the following jenkins job:
http://jenkins.qa.ubuntu.com/job/mir-autolanding/2148/
Executed test runs:
    FAILURE: http://jenkins.qa.ubuntu.com/job/mir-android-vivid-i386-build/4955/console
    SUCCESS: http://jenkins.qa.ubuntu.com/job/mir-clang-vivid-amd64-build/3861
    SUCCESS: http://jenkins.qa.ubuntu.com/job/mir-mediumtests-vivid-touch/4901
    FAILURE: http://jenkins.qa.ubuntu.com/job/mir-mediumtests-wily-touch/857/console
    SUCCESS: http://jenkins.qa.ubuntu.com/job/mir-wily-amd64-autolanding/701
        deb: http://jenkins.qa.ubuntu.com/job/mir-wily-amd64-autolanding/701/artifact/work/output/*zip*/output.zip
    None: http://jenkins.qa.ubuntu.com/job/mir-wily-i386-ci/855/console
    SUCCESS: http://jenkins.qa.ubuntu.com/job/mir-mediumtests-builder-vivid-armhf/4901
        deb: http://jenkins.qa.ubuntu.com/job/mir-mediumtests-builder-vivid-armhf/4901/artifact/work/output/*zip*/output.zip
    SUCCESS: http://jenkins.qa.ubuntu.com/job/mir-mediumtests-runner-touch/7466
    SUCCESS: http://s-jenkins.ubuntu-ci:8080/job/touch-flash-device/25331
    FAILURE: http://jenkins.qa.ubuntu.com/job/mir-mediumtests-builder-wily-armhf/858/console

review: Needs Fixing (continuous-integration)

=== modified file 'src/common/dispatch/threaded_dispatcher.cpp'
--- src/common/dispatch/threaded_dispatcher.cpp	2015-06-17 05:20:42 +0000
+++ src/common/dispatch/threaded_dispatcher.cpp	2015-11-18 14:59:20 +0000
@@ -202,6 +202,8 @@
         {
             if (poll(&waiter, 1, -1) < 0)
             {
+                if (errno == EINTR)
+                    continue;
                 BOOST_THROW_EXCEPTION((std::system_error{errno,
                                                          std::system_category(),
                                                          "Failed to wait for event"}));