Re: [ros-dev] re: ps/kill.c change

[Alex Ionescu]

Hartmut Birr wrote:

>  Alex Ionescu wrote:
>
>   
>
> >  Hi,
> >
> > Sorry but I accidentally lost 60 emails including the one I'm supposed
> > to reply to.
> >
> > Hartmut, you have done a recent change in kill.c in which you change
> > the APC inside PspTerminateThreadByPointer to a user-mode APC. This is
> > incorrect and I don't understand why it was done... furthermore, I've
> > even documented a source of information which proves my code was
> > correct (on top of the function header), so why did you change it?
> >
> >     
> >  
> Hi,
>
> the thread termination APC must be a user mode APC. The kernel routine
> (PsExitSpecialApc) calls PspExitThread. PspExitThread can only be called
> if no cleanup is necessary like freeing pool memory or dereferencing
> kernel mode objects. The only point for the thread terminating is the
> return to user mode after a system call or at the end of an exception or
> hardware interrupt. PspExitThread can not be called from a kernel mode
> APC, because the apc is delivered at any point where the irql drops
> below APC_LEVEL. The thread may have referenced some kernel objects at
> this point, may have allocated pool memory or may have locked the kernel
> address space and so on. Currently there exist some situations where it
> isn't possible to terminate a thread if the thread runs in kernel mode.
> Such a situation is if the thread waits on an object which will not be
> signaled.
>
> - Hartmut
>   
>  
Hi,

Your reply makes perfect sense and now that I look at it, I see that 
there is a certain part of the code that I forgot to write (I wrote a 
comment on it)...however I insist that the first APC queued is Kernel, 
you can see it for yourself in the NT source code snippet...but in the 
end it does become a user-mode APC...I'll write up a patch.

Best regards,
Alex Ionescu