Re: [6/7] vcomp: Implement _vcomp_enter_critsect and _vcomp_leave_critsect.

[Nikolay Sivov]

On 07.08.2015 9:22, Sebastian Lackner wrote:
> However, this does not fully prevent a
> leak when frequently unloading / reloading a library using OpenMP... sounds a bit
> like a design flaw to me.

You could keep a list of allocations to fix that if it's really a problem.

[6/7] vcomp: Implement _vcomp_enter_critsect and _vcomp_leave_critsect.

[Sebastian Lackner]

On 07.08.2015 08:57, Nikolay Sivov wrote:
> On 07.08.2015 9:22, Sebastian Lackner wrote:
> > However, this does not fully prevent a
> > leak when frequently unloading / reloading a library using OpenMP... sounds a bit
> > like a design flaw to me.
>
> You could keep a list of allocations to fix that if it's really a problem.

Vcomp wouldn't get notifications for loads/unloads of other libraries, and we also don't
know which critical sections belong to which library. A list of allocations could only
be used to clean up on process exit. If it is really a problem in practice, I would
guess that Windows is affected in a similar way.

[6/7] vcomp: Implement _vcomp_enter_critsect and _vcomp_leave_critsect.

[Nikolay Sivov]

On 07.08.2015 10:04, Sebastian Lackner wrote:
> On 07.08.2015 08:57, Nikolay Sivov wrote:
> > On 07.08.2015 9:22, Sebastian Lackner wrote:
> > > However, this does not fully prevent a
> > > leak when frequently unloading / reloading a library using OpenMP... sounds a bit
> > > like a design flaw to me.
> >
> > You could keep a list of allocations to fix that if it's really a problem.
>
> Vcomp wouldn't get notifications for loads/unloads of other libraries, and we also don't
> know which critical sections belong to which library. A list of allocations could only
> be used to clean up on process exit. If it is really a problem in practice, I would
> guess that Windows is affected in a similar way.

Is it possible it allocates one section per thread or something like 
that? E.g. what do two consecutive _vcomp_enter_critsect() calls return 
for NULL input, is it same pointer every time for example?

[6/7] vcomp: Implement _vcomp_enter_critsect and _vcomp_leave_critsect.

[Sebastian Lackner]

On 07.08.2015 09:13, Nikolay Sivov wrote:
> On 07.08.2015 10:04, Sebastian Lackner wrote:
> > On 07.08.2015 08:57, Nikolay Sivov wrote:
> > > On 07.08.2015 9:22, Sebastian Lackner wrote:
> > > > However, this does not fully prevent a
> > > > leak when frequently unloading / reloading a library using OpenMP... sounds a bit
> > > > like a design flaw to me.
> > >
> > > You could keep a list of allocations to fix that if it's really a problem.
> >
> > Vcomp wouldn't get notifications for loads/unloads of other libraries, and we also don't
> > know which critical sections belong to which library. A list of allocations could only
> > be used to clean up on process exit. If it is really a problem in practice, I would
> > guess that Windows is affected in a similar way.
>
> Is it possible it allocates one section per thread or something like that? E.g. what do two consecutive _vcomp_enter_critsect() calls return for NULL input, is it same pointer every time for example?

No, it returns a different pointer each time. It also returns a new pointer when calling
_vcomp_enter_critsect() after the critical section was manually set to zero. Different critical
sections are necessary because all "#pragma omp critical" regions should be independent,
except they have the same name (then the compiler would use the same static variable).