Re: Unwarranted assumption in tst-waitid, or a kernel bug?

[Roland McGrath <roland at redhat dot com>]

> Well. Until today I knew absolutely nothing about ipc/mqueue.c, so you
> shouldn't trust me (and in fact I spent some time trying to find the
> implementation of mq_send/etc in glibc's sources ;)

I haven't really looked at mq stuff before either.

Jakub wrote this test, so maybe he can explain some of its intents.

> However. I can easily misinterpret this code, but it seems that
> sys_mq_timedsend() doesn't necessarily sends a signal if the caller
> of sys_mq_timedreceive() already sleeps ?

That's correct.  And that's what POSIX says it should do (under mq_notify):

      If a process has registered for notification of message arrival
      at a message queue and some thread is blocked in mq_receive() or
      mq_timedreceive() waiting to receive a message when a message
      arrives at the queue, the arriving message shall satisfy the
      appropriate mq_receive() or mq_timedreceive(), respectively. The
      resulting behavior is as if the message queue remains empty, and
      no notification shall be sent.


Thanks,
Roland