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From "Neil Conway" <neil.con...@gmail.com>
Subject Re: Review Request 39949: Document and simplify libprocess initialization synchronization logic.
Date Wed, 04 Nov 2015 19:58:54 GMT


> On Nov. 4, 2015, 7:25 p.m., Neil Conway wrote:
> > Can we test that more thoroughly than just "make check"? e.g., if there's a unit
test that tries to enter this logic with multiple threads at once, running that with gtest_repeat=1000
would be nice.
> 
> Joseph Wu wrote:
>     There are tons of methods in libprocess that call `process::initialize` as a side-effect,
but at the same time, the libprocess test suite starts out with an essentially race-free init
call (See: https://github.com/apache/mesos/blob/master/3rdparty/libprocess/src/tests/main.cpp#L52).
 So any `--gtest_repeat` or `--gtest_shuffle` won't actually test the init code.  (The master
and agent also call init once on startup.)
>     
>     I'm not sure how valuable it will be to, say, to spawn a bunch of threads that call
`process::initialize`.  Do you have any suggestions?

You could hackup tests/main.cpp::main() to test concurrent calls to process::initialize()
-- i.e., 

```if (getenv("TEST_LIBPROCESS_INIT")) { for (int i = 0; i < 100; i++) { /* spawn thread
*/ process::initialize(); } } }```


- Neil


-----------------------------------------------------------
This is an automatically generated e-mail. To reply, visit:
https://reviews.apache.org/r/39949/#review105115
-----------------------------------------------------------


On Nov. 4, 2015, 6:58 p.m., Joseph Wu wrote:
> 
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://reviews.apache.org/r/39949/
> -----------------------------------------------------------
> 
> (Updated Nov. 4, 2015, 6:58 p.m.)
> 
> 
> Review request for mesos, Benjamin Hindman and Joris Van Remoortere.
> 
> 
> Repository: mesos
> 
> 
> Description
> -------
> 
> The initialization synchronization logic contains three conditions, which check:
> 1) Was `initialize` called and is it done?
> 2) Was `initialize` called and is it not done?
> 3) Are you the first to call `initialize`?
> 
> Condition (3) uses `compare_exchange_strong` between `initialized` and `false`.  This
returns `true` (and sets `initialized` to true) iff the caller is the first to reach that
expression.
> 
> The second simultaneous caller of `initialize` will either satisify condition (2) or
(3) and then wait on `initializing`.  For the second caller, (2) and (3) are identical because
`compare_exchange_strong` between `true` and `false` will always return false, thereby putting
the second caller into the waiting loop.
> 
> 
> Diffs
> -----
> 
>   3rdparty/libprocess/src/process.cpp a94712b9ac3b60fb047b3a5a4d84a56fa4d02313 
> 
> Diff: https://reviews.apache.org/r/39949/diff/
> 
> 
> Testing
> -------
> 
> `make check`
> 
> 
> Thanks,
> 
> Joseph Wu
> 
>


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