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Re: What does "Execution timeout is: $test_timeout" mean?


From: Jacob Bachmeyer
Subject: Re: What does "Execution timeout is: $test_timeout" mean?
Date: Wed, 02 Dec 2020 21:48:04 -0600
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.8.1.22) Gecko/20090807 MultiZilla/1.8.3.4e SeaMonkey/1.1.17 Mnenhy/0.7.6.0

Jonathan Wakely wrote:
Hi,

[...]

If I set test_timeout in ~/.dejagnurc or site.exp then I do indeed see
the value change. But it doesn't do anything. I can set test_timeout
to 2 second, and tests that sleep for 20 seconds or more will still
PASS and not timeout (as long as $tool_timeout is large enough).

Evidently, the GCC testsuite is overriding that setting.

The docs added by that patch say that $test_timeout is "the amount of
time (in seconds) to wait for a remote test to complete" which doesn't
match my observations. Is it because I'm testing locally, not
remotely? If that value only affects remote tests, why does DejaGnu
print "Execution timeout is: $test_timeout" to the logs
unconditionally? It's unhelpful (i.e. downright confusing) to log it
if it's not actually relevant.

DejaGnu *does* know about the "real" timeout, because the remote_exec
proc in remote.exp has already handled it and logged it via this
command:

verbose -log "Executing on $hostname: $program $pargs $inp $outp (timeout = $timeout)" 2

I see that in my logs, and the $timeout value is the one I've set via
$tool_timeout and actually works. If I set that to a low value, my
tests timeout and FAIL. That timeout is the total time for both
compiling and running the test.

When I use -v -v -v with dejagnu-1.6.1 and set GCC's tool_timeout=30
and test_timeout=2 I see the output in the attached extract from the
log. The lines beginning with ================ are printed by the test
itself, showing it sleeps for 20 seconds. Despite DejaGnu telling me
the execution timeout is 2, the test passes. Either the execution
timeout is not used, or the timeout is not working.

DejaGnu seems to only implement one timeout at a time, so the use of GCC's tool_timeout (probably) overrides DejaGnu's own test_timeout. The underlying Expect works this way, and DejaGnu does not currently select from the minimum of multiple timeouts. Also, DejaGnu's timeouts are meant to catch hung tests, so they are reset whenever output arrives from the test case. (That is probably not part of this issue here, but it is important to remember, especially since there are also places in DejaGnu where some number of timeouts are permitted to occur before an error is actually reported.)

Could unix.exp stop logging that line unconditionally if it's not
true?

Is it supposed to be true? Is the timeout failing to fire? Is it not
relevant for local tests?

I'm very confused.

I am also confused, so I have added this to my list of future issues to address once I learn enough to understand (and document!) DejaGnu's remote testing code.


-- Jacob




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