[SCM] Samba Shared Repository - branch master updated - release-4-0-0alpha7-557-gd380c49

[Stefan (metze) Metzmacher]

Hi Tridge,

>  > >     fixed a logic bug in the tevent nesting code
>  > >     
>  > >     The event nesting code never triggered as nesting.level was never
>  > >     greater than 1. The main event loop needs to increase the nesting
>  > >     level by 1.
>  > 
>  > That was desired, why do you want to be called if there's no nesting?
>  > you do if (unixuid_nesting_level == 0) return; anyway.
> 
> The code as it was previously would only call the hook if we had two
> levels of nesting. ie. it would call it when we had this:
> 
>  - main loop
>    - call to event_loop_once
>      - call to event_loop_once
>        - calls hook

tevent_loop_wait() calls tevent_loop_once() internally,
see the tevent_common_loop_once() function.

so for samba it was:

level 1: tevent_loop_wait() (internally also tevent_loop_once())
level 2:   tevent_loop_once() -> calling the hook with level == 2.
level 3:     tevent_loop_once() -> callling the hook with level == 3.
...

for smbtorture it was:

level 1: tevent_loop_once()
level 2:   tevent_loop_once() -> calling the hook with level == 2.
level 3:     tevent_loop_once() -> calling the hook with level == 3.

Currently we call the hook for each level, but the above was my first
design. Now we have the question if we want to call the hook at
level > 1, or if we want to call it always and let the hook decide if it
makes level 1 a noop.

> It was just a simple off by 1 error, as the check was for > 1, which
> meant it only triggered when the nesting was 2 or greater. It started
> at zero. 
> 
>  > If we change it to call the hook at level 0, we should change that in
>  > tevent_loop_once() and not in tevent_loop_wait().
> 
> no, because then we'll get the hook code called in top level code that
> calls event_loop_once, such as the smbtorture code.
> 
>  > >     I also added a paranoia check to the nesting setup call. The API as
>  > >     currently written cannot support multiple nesting hooks, so we need to
>  > >     abort if multiple hooks are tried.
>  > 
>  > I think we should have global in vfs_unixid.c which remembers that we
>  > already set the hook and not reset it on each tree connect.
> 
> The point of that paranoia check was not for the existing vfs code, it
> was for future uses of that API. The API is now a public part of
> tevent, and may be used by other libraries or modules. The first time
> we used a library like that we would have had silent corruption. 
> 
> It would be perfectly possible to re-do the implementation of this
> function so that it can cope with multiple pieces of code on the same
> event context that need a hook (we could have a linked list of
> hooks). By having this paranoia check we will know when we need to
> re-do the implementation when we first hit this situation.

I think we can keep it simple and let the application add a wrapper
that dispatches multiple hooks.

metze

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 252 bytes
Desc: OpenPGP digital signature
Url : http://lists.samba.org/archive/samba-technical/attachments/20090320/1050d514/signature.bin