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Problem Report 0300 Details

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    Problem Report Number 0300
    Submitter's Classification Test Suite problem
    State Resolved
    Resolution Permanent Interpretation (PIN)
    Problem Resolution ID PIN.X.0016
    Raised 1993-12-04 08:00
    Updated 2003-03-13 08:00
    Published 1994-01-19 08:00
    Product Standard Internationalised System Calls and Libraries (XPG4)
    Certification Program The Open Brand certification program
    Test Suite VSX4 version 4.2.4
    Test Identification POSIX.os/devclass/tcsendbrea 9-12
    Specification System Interfaces and Headers Issue 4
    Location in Spec See Problem Text
    Problem Summary PIN4.016 Tests 9 through 12 fail and/or are unresolved when they are run as members of the tcsendbrea testset. When run individually or as a sequence 9-12 or even 7-12, without running any of the remaining tes...
    Problem Text
    *********************************************************************

    Tests 9 through 12 fail and/or are unresolved when they are run as
    members of the tcsendbrea testset. When run individually or as a
    sequence 9-12 or even 7-12, without running any of the remaining
    tests (ie: 1-6), they all pass successfully.

    Explanation for the above is as follows:

    a) the tcsendbrea testset begins by calling termios_prep() which
    will make the parent process become a session leader, initializes
    and open the terminal ports using file descriptors tty_fildes and
    loop_fildes, and then makes tty_fildes the session leader's
    controlling terminal.

    b) tests 1-6 are child processes, they all call break_up() with
    break_prep_mode set to USE_CTTY. break_up() creates a new session
    leader using setsid(), reopen loop_fildes using opnctl(), thereby
    establishing loop_fildes as a controlling terminal of the new
    session. Tests 1-6 then verify various tcsendbreak assertions on
    tty_fildes.

    c) Test 9 also calls break_prep() but with break_prep_mode set to
    USE_NON_CTTY. Break_prep() in this case does not reopen the loopback
    port but assigns to loop_fildes its previous value saved in
    loop_fildes_keep during termios_prep().

    It is to be noted at this point that in our implementation, when a
    process becomes a session leader and acquires a controlling terminal,
    when the process exits, the file descriptors of the controlling
    terminal are disassociated on a system wide basis.

    Given the above behavior, the port associated with loop_fildes is
    disconnected upon exit of test 6, and when test 9 later on tries
    to send a break to loop_fildes using tcsendbreak(), the test fails
    to perform the action since the file descriptor is no longer valid.

    When test 9 is run individually, the testset is now reduced to
    termios_prep() and test9(). tty_fildes and loop_fildes are valid
    file descriptors after the termios_prep() call and test 9 executes
    successfully.

    The assertion for test 9, "when tcsendbreak() is called from a
    foreground process, and when fildes refers to a non-controlling
    terminal, the tcsendbreak actions shall be performed", is verified
    when test 9 is run individually because the action is made on
    loop_fildes which in this case is not being associated with a
    controlling terminal.

    d) tests 10, 11, and 12 begin by performing tcflush() on the
    loop_fildes file descriptor. The three tests are getting Unresolved
    because tcflush() is called on an invalid file descriptor which port
    has being disconnected after test 6 given our system wide behavior,
    and hence giving EIO errors as if modem disconnect.

    When test #10 through #12 are run individually or even in the
    sequence 9-12, they all run successfully.


    From the above observations it is apparent that the failures are
    not due to a non-conforming tcsendbreak() API, but rather to the
    controlling terminal behavior described in XPG4 as follows:

    "When a controlling process terminates, the controlling terminal
    is disassociated from the current session, allowing it to be
    acquired by a new session leader. Subsequent access to the terminal
    by other processes in the earlier session may be denied, with
    attempts to access the terminal treated as if modem disconnect had
    been sensed"

    Although it appears that XPG4 only requires terminal disassociation
    to affect processes in the session whose leader had exited, it also
    never specifed that processes in subsequent sessions must be able
    to access the terminal associated with the exited controlling process.

    This seems to be the required behavior from the tcsendbrea testset.

    We believe our system behavior is not in conflict with what is being
    specified in XPG4, and that such behavior should be considered as an
    extension. This is a BSD behaviour we have had for years, and had not
    affected our conformance to XPG until VSX4.

    We request that a waiver be granted to the above failures which are
    due to a test strategy that is based on an assertion that is not
    being specified by the Standard.

    *********************************************************************
    Test Output
    ************************************************************************
    /tset/POSIX.os/devclass/tcsendbrea/T.tcsendbrea 9 Failed

    Test Description:
    If general terminal interface supported:
    when tcsendbreak() is called from a foreground process, and when
    fildes refers to a non-controlling terminal, the tcsendbreak
    actions shall be performed.
    Posix Ref: Component TCSENDBREAK Assertion 7.2.2.2-X1(C)

    Test Strategy:
    OPEN and initialise terminal file and loop back file
    CREATE process pair
    PARENT process:
    SLEEP for WAITTIME to allow break to generate SIGINT signal
    VERIFY that SIGINT signal was received
    CHILD process:
    SET time out for WAITTIME
    SEND a break using tcsendbreak(loop_fildes, 0)
    VERIFY that tcsendbreak() returned zero.

    Test Information:
    tcsendbreak() action was not performed (SIGINT not received)

    *********************************************************************
    /tset/POSIX.os/devclass/tcsendbrea/T.tcsendbrea 10 Unresolved

    Test Description:
    If general terminal interface supported:
    when tcsendbreak() is called from a background process, that is not
    blocking or ignoring the SIGTTOU signal, and when fildes refers to
    a non-controlling terminal, the tcsendbreak actions shall be
    performed.
    Posix Ref: Component TCSENDBREAK Assertion 7.2.2.2-X2(C)

    Test Information:
    tcflush() failed on VSX_TERMIOS_LOOP - errno 5 (EIO)

    *********************************************************************
    /tset/POSIX.os/devclass/tcsendbrea/T.tcsendbrea 11 Unresolved

    Test Description:
    If general terminal interface supported:
    when tcsendbreak() is called from a background process, that is
    blocking the SIGTTOU signal, and when fildes refers to a non-
    controlling terminal, the tcsendbreak actions shall be performed.
    Posix Ref: Component TCSENDBREAK Assertion 7.2.2.2-X3(C)

    Test Information:
    tcflush() failed on VSX_TERMIOS_LOOP - errno 5 (EIO)

    *********************************************************************
    /tset/POSIX.os/devclass/tcsendbrea/T.tcsendbrea 12 Unresolved

    Test Description:
    If general terminal interface supported:
    when tcsendbreak() is called from a background process, that is
    ignoring the SIGTTOU signal, and when fildes refers to a non-
    controlling terminal, the tcsendbreak actions shall be performed.
    Posix Ref: Component TCSENDBREAK Assertion 7.2.2.2-X4(C)

    Test Information:
    tcflush() failed on VSX_TERMIOS_LOOP - errno 5 (EIO)

    *********************************************************************

    Review Information

    Review Type TSMA Review
    Start Date null
    Completed null
    Status Complete
    Review Recommendation No Resolution Given
    Review Response
    This request raises the question as to which processes may be affected
    when the controlling terminal is disassociated from a session because
    the session leader has exited. The XBD Page 114 states that once a
    controlling process (session leader) terminates other processes in the
    session may be denied subsequent access to the terminal. The XPG is
    silent as to the ability of processes which are not in the session
    which has terminated to access the terminal after session termination.

    However, the write() system call does state that an EIO error may also
    be returned under implementation-dependent conditions. This phrase is
    not repeated for the tcsendbreak() call, though it is believed that this
    is an unintentional omission.

    The VSX test suite is well behaved on most systems which do not disassociate
    processes outside of the session and relies on this association being
    retained. The XPG is silent about this being a requirement and it could
    be considered that the disassociation of processes outside the session
    is a valid extension to the XPG specification.

    On balance this seems to be a valid grey area and a permanent interpretation
    is recommended. However, since this is an issue affected by the POSIX
    specification, the X/Open K/RT working group may consider it advisable to
    forward this request through the POSIX.1 interpretations forum.

    Review Type SA Review
    Start Date null
    Completed null
    Status Complete
    Review Resolution Permanent Interpretation (PIN)
    Review Conclusion
    A permanent interpretation is granted.

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