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From "Joseph Wu" <jos...@mesosphere.io>
Subject Re: Review Request 39949: Document and simplify libprocess initialization synchronization logic.
Date Sat, 07 Nov 2015 02:00:01 GMT


> On Nov. 6, 2015, 5:50 p.m., Mesos ReviewBot wrote:
> > Bad patch!
> > 
> > Reviews applied: [39948]
> > 
> > Failed command: ./support/apply-review.sh -n -r 39948
> > 
> > Error:
> >  2015-11-07 01:50:12 URL:https://reviews.apache.org/r/39948/diff/raw/ [2087/2087]
-> "39948.patch" [1]
> > error: patch failed: 3rdparty/libprocess/src/process.cpp:739
> > error: 3rdparty/libprocess/src/process.cpp: patch does not apply
> > Failed to apply patch

Hmm... That's weird.  I can apply just fine on the head commit (at the time, c68963297c9bec52cd6efb269454340b824ae931).


- Joseph


-----------------------------------------------------------
This is an automatically generated e-mail. To reply, visit:
https://reviews.apache.org/r/39949/#review105561
-----------------------------------------------------------


On Nov. 6, 2015, 2:11 p.m., Joseph Wu wrote:
> 
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://reviews.apache.org/r/39949/
> -----------------------------------------------------------
> 
> (Updated Nov. 6, 2015, 2:11 p.m.)
> 
> 
> Review request for mesos, Benjamin Hindman, Joris Van Remoortere, and Neil Conway.
> 
> 
> Bugs: MESOS-3820
>     https://issues.apache.org/jira/browse/MESOS-3820
> 
> 
> Repository: mesos
> 
> 
> Description
> -------
> 
> * Renamed `initialized` to `initialize_started`.
> * Renamed `initializing` to `initialize_complete`.
> * Removed the (2) condition, described below: 
> 
> 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`
> 
> Replaced `process::initialize();` in `3rdparty/libprocess/src/tests/main.cpp` with:
> ```
> 
>   const size_t numThreads = 50;
> 
>   std::thread* runningThreads[numThreads];
> 
>   // Create additional threads.
>   for (size_t i = 0; i < numThreads; i++) {
>     runningThreads[i] = new std::thread([]() {
>       process::initialize();
>     });
>   }
> 
>   for (size_t i = 0; i < numThreads; i++) {
>     runningThreads[i]->join();
>     delete runningThreads[i];
>   }
> ```
> (Also added `#include <thread>` to the header).
> 
> Rebuilt `libprocess-tests` with the modification and ran it a few times.
> `3rdparty/libprocess/libprocess-tests`
> 
> 
> Thanks,
> 
> Joseph Wu
> 
>


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