RTEMS | Need to invalidate posix message queue object id when delete mq (!364)

[Joel Sherrill (@joel)]

Joel Sherrill commented on a discussion on testsuites/psxtests/psxmsgq01/init.c: https://gitlab.rtems.org/rtems/rtos/rtems/-/merge_requests/364#note_122731

 >    fatal_posix_service_status( status, 0, "mq_close duplicate message queue");
 >    status = mq_close( Test_q[CLOSED].mq );
 >    fatal_posix_service_status( status, 0, "mq_close message queue");
 > +  /*
 > +   * EBADF - Close a queue that is already closed.
 > +   */
 > +  status = mq_close( Test_q[CLOSED].mq );
 > +  fatal_posix_service_status( status, -1, "mq_close error return status");
 > +  fatal_posix_service_status( errno, EBADF, "mq_close errno EBADF");

I think the change is correct because it is invalidating the id passed in to mq_close(). The test changes are likely ok but not exercising what changed fully. This use case may require a different approach with multiple calls. mq_unlink() takes the mq out of the namespace. You cannot mq_open() it again but all mq descriptors from previous opens on the same mq are valid until all are closed. How about something like this:

+ mq_open
+ mq_unlink
+ mq_open again -> should fail. 
+ mq_close -> OK, should delete since no uses
+ mq_close -> should fail, mq id is now invalid

The second mq_open is what verifies the mq name is gone. The first mq_close() working says the id is ok. The second says the id is no longer OK.

mq_getattr() is a call which could be used to verify if an id is valid or not.

-- 
View it on GitLab: https://gitlab.rtems.org/rtems/rtos/rtems/-/merge_requests/364#note_122731
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