[PATCH] D14706: [lit] Implement support of per test timeout in lit.

[Chris Matthews via llvm-commits]

I think needing a package that is not included in the Python standard release this is a serious issue. lit has no dependencies. That makes it easy to build and test anywhere. 

> On Dec 5, 2015, at 2:36 AM, Dan Liew <dan at su-root.co.uk> wrote:
> 
> delcypher added a comment.
> 
> In http://reviews.llvm.org/D14706#303269, @MatzeB wrote:
> 
>> This is a good feature to have.
> 
> 
> Thanks for taking a look
> 
>> I think this implementation will not apply a timeout to the TestRunner.py:executeShCmd codepath (which seems to be a /bin/sh emulation for windows users).
> 
> 
> That is incorrect. The timeout is applied on all code paths when the timeout is
> enabled. For the `executeShCmd()` (internal shell) case the timeout is
> implemented in a different way to `lit.util.executeCommand()` (external shell)
> but this definitely works (at least on Linux). I added tests cases for the three
> cases: External Shell, Internal Shell and GTest.
> 
>> The requirement of an external python package is unfortunate, what about things possible with built-in python libraries such as "os.kill(pid, signal.SIGKILL)" or "resource.setrlimit(resource.RLIMIT_CPU ...)"?
> 
> 
> While it is not impossible to remove the dependency on the `pustil` module,
> doing so would be difficult due to platform differences. The issue here is
> that when killing a process, we must kill the process and its children (and
> their children and so on...). If we don't do this we will have processes left
> behind that can continue executing past the timeout.
> 
> This is even an issue in the most basic case where we use the external shell to
> execute a single command because the parent process is the shell and the child
> is the actual command we wanted to run.
> 
> There are ways to achieve killing of a group of processes on Linux (not sure
> about OSX) by having the parent be in its own session (via
> `preexe_fn=cos.setsid()`) and then later killing using `os.killpg()` but
> that isn't available on Windows and so isn't portable. The aproach I use is
> because `pustil` provides a way to easily iterate over a process's children
> and kill them. I don't know of any cross platform way of doing this using just
> Python's standard library.
> 
> I have kept the dependency on `pustil` confined to the
> `lit.util.killProcessAndChildren()` function so in the future we could
> potentially remove the dependency.  It's not something I can do right now
> though as I don't have access to a Windows or OSX machine.
> 
> 
> http://reviews.llvm.org/D14706
> 
> 
>