RE: [PATCH v4] libgfortran: Replace mutex with rwlock

["Zhu, Lipeng" <lipeng.zhu@intel.com>]

> 
> > Hi Thomas,
> >
> > >
> > > Hi Lipeng,
> > >
> > > > May I know any comment or concern on this patch, thanks for your
> > > > time
> > > > 😄
> > >
> > > Thanks for your patience in getting this reviewed.
> > >
> > > A few remarks / questions.
> > >
> > > Which strategy is used in this implementation, read-preferring or
> > > write- preferring?  And if read-preferring is used, is there a
> > > danger of deadlock if people do unreasonable things?
> > > Maybe you could explain that, also in a comment in the code.
> > >
> >
> > Yes, the implementation use the read-preferring strategy, and comments
> > in code.
> > When adding the test cases, I didn’t meet the situation which may
> > cause the deadlock.
> > Maybe you can give more guidance about that.
> >
> > > Can you add some sort of torture test case(s) which does a lot of
> > > opening/closing/reading/writing, possibly with asynchronous I/O
> > > and/or pthreads, to catch possible problems?  If there is a system
> > > dependency or some race condition, chances are that regression testers
> will catch this.
> > >
> >
> > Sure, as your comments, in the patch V6, I added 3 test cases with
> > OpenMP to test different cases in concurrency respectively:
> > 1. find and create unit very frequently to stress read lock and write lock.
> > 2. only access the unit which exist in cache to stress read lock.
> > 3. access the same unit in concurrency.
> > For the third test case, it also help to find a bug:  When unit can't
> > be found in cache nor unit list in read phase, then threads will try
> > to acquire write lock to insert the same unit, this will cause duplicate key
> error.
> > To fix this bug, I get the unit from unit list once again before insert in write
> lock.
> > More details you can refer the patch v6.
> >
> 
> Could you help to review this update? I really appreciate your assistance.
> 

Hi Thomas, Bernhard,

Could you help to review this update?  Any concern will be appreciated.

Regards,
Lipeng Zhu
> > > With this, the libgfortran parts are OK, unless somebody else has
> > > more comments, so give this a couple of days.  I cannot approve the
> > > libgcc parts, that would be somebody else (Jakub?)
> > >
> > > Best regards
> > >
> > > 	Thomas
> > >
> >
> > Best Regards,
> > Lipeng Zhu
> 
> Best Regards,
> Lipeng Zhu