Add a test for cancelling an active AIO request on a socket.

[jhb]

Summary

Add a test for cancelling an active AIO request on a socket.

The older AIO code awakened all pending AIO requests on a socket
when any data arrived. This could result in AIO daemons blocking on
an empty socket buffer. These requests could not be cancelled
which led to a deadlock during process exit. This test reproduces
this case. The newer AIO code is able to cancel the pending AIO
request correctly.

Test Plan

• Run the test on an old kernel. Not only does the process hang and refuse to exit, but the kernel hangs on reboot.

[jhb]

One question I have is if we want to check in a test that has such a negative effect on broken systems.

[ngie]

The test portion looks ok, minus the minor nit in the Makefile.

tests/sys/aio/Makefile

7 ↗

(On Diff #10713)

Could you please put this on a separate line?

I need to sort this list too >_>...

[ngie]

In D4363#91952, @jhb wrote:

One question I have is if we want to check in a test that has such a negative effect on broken systems.

The test's good. It might be a good idea to key whether or not it should be skipped based on FreeBSD_version though.

[jhb]

In D4363#93334, @ngie wrote:

In D4363#91952, @jhb wrote:

One question I have is if we want to check in a test that has such a negative effect on broken systems.

The test's good. It might be a good idea to key whether or not it should be skipped based on FreeBSD_version though.

I've finally gotten back to this. Should that be a runtime check of the current kernel's version? If so, do we have an existing ATF helper for that ala ATF_REQUIRE_MODULE. I'm thinking something like:

ATF_REQUIRE_OSRELDATE(1100000) and having it skip if the kern.osreldate is older?

[jhb]

Rework this change to only include the test. The FIFO behavior was included
in the AIO rework committed recently.

• Add a test for the hang when two reads are queued.
• Update comment for what happened when I ran the test.
• Fix copyright.
• Implement ATF_REQUIRE_OSRELDATE() and PLAIN_REQUIRE_OSRELDATE().
• Use ATF_REQUIRE_OSRELDATE().
• Compile.

[jhb]

• Style and misc fixes.

[jhb]

• Rebase
• Move test over into aio_test.

[ngie]

tests/freebsd_test_suite/macros.h

55–67 ↗

(On Diff #14756)

This seems like a bit of an unnecessary hoop to jump through, especially because it can be changed by jail(8). What I was proposing was something more along the lines of the following in the test(s):

#if __FreeBSD_version < X`
    atf_tc_skip("not running test on system because it's too old");
#endif

We could make an official macro for it that doesn't require the kern.osrelease poking though...

[jhb]

tests/freebsd_test_suite/macros.h

55–67 ↗

(On Diff #14756)

If you think a compile time test (vs run-time) is fine I'm ok with that.

[jhb]

• Drop OSRELDATE macros and test __FreeBSD_version at compile time.