[lldb-dev] Race in TestLldbGdbServer and TestGdbRemote*

Tamas Berghammer tberghammer at google.com
Wed Mar 25 04:56:56 PDT 2015

Hi Everybody,

Occasionally I see failures in TestLldbGdbServer and in TestGdbRemote* most
likely caused by a race condition in the test runner hitting an edge case
in these tests. As far as I understand the problem is that each test case
compile the same source file (main.cpp) to main.o and then to a.out and
when the test is finished it removes these files. The problem starts when
multiple test case running at the same time trying to do it because it is
possible that one of the test case just compiled it's executable and then
an other test case (running in a different process) immediately removes it
causing a failure in process launch. This issue causing significant noise
on our build bots so we should fix it as soon as possible.

One possible solution (what is used in several similar cases) is to use a
different executable name for each test case what reduce the chance of the
described scenario but it isn't eliminates it completely because the name
of the intermediate build file (main.o) can't be changed easily from the
test case.

A second possible solution is to merge all test case into a single file
what will prevent the test runner (dosep.py) to execute them in parallel
but this can have some negative effect on the speed of the tests.

A third option to move each test case into it's own directory to eliminate
the possibility for a source file conflict but I am not sure if it is
possible without duplicating the source file of the inferior (quite
complicated) into each folder.

I am looking for some advice about what approach you suggest to get rid of
this race in the tests.

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