KeRundownThread question

[Hartmut Birr]

Hi,

in KeRundownThread  is an ASSERT statement. What is the reason for that?
ApcDisable is never changed. It is always 1 for mutex objects and always
0 for mutant objects. If a mutant object is on the list, ros does crash.

- Hartmut

Index: ntoskrnl/ke/kthread.c
===================================================================
--- ntoskrnl/ke/kthread.c       (revision 14297)
+++ ntoskrnl/ke/kthread.c       (working copy)
@@ -360,7 +360,7 @@

         /* Get the Mutant */
         Mutant = CONTAINING_RECORD(CurrentEntry, KMUTANT, MutantListEntry);
-        ASSERT(Mutant->ApcDisable);
+//        ASSERT(Mutant->ApcDisable);

[Alex Ionescu]

Hartmut Birr wrote:

>  Hi,
>
> in KeRundownThread  is an ASSERT statement. What is the reason for that?
> ApcDisable is never changed. It is always 1 for mutex objects and always
> 0 for mutant objects. If a mutant object is on the list, ros does crash.
>
> - Hartmut
>
> Index: ntoskrnl/ke/kthread.c
> ===================================================================
> --- ntoskrnl/ke/kthread.c       (revision 14297)
> +++ ntoskrnl/ke/kthread.c       (working copy)
> @@ -360,7 +360,7 @@
>
>          /* Get the Mutant */
>          Mutant = CONTAINING_RECORD(CurrentEntry, KMUTANT, MutantListEntry);
> -        ASSERT(Mutant->ApcDisable);
> +//        ASSERT(Mutant->ApcDisable);
>
>
>   
>  
It should actually be a bugcheck with THREAD_TERMINATE_HELD_MUTEX, but I 
only discovered this weird Bugcode much later after coding this. See 
some information here:

http://groups-beta.google.com/group/comp.os.ms-windows.nt.misc/browse_frm/t…

here:

/
// MessageId: *THREAD_TERMINATE_HELD_MUTEX*
//
// MessageText:
//
//  A kernel thread terminated while holding a mutex
//

Best regards,
Alex Ionescu

[Hartmut Birr]

Alex Ionescu wrote:

>   It should actually be a bugcheck with
> THREAD_TERMINATE_HELD_MUTEX, but
>  I only discovered this weird Bugcode much later after coding this. See
>  some information here:
>
>
> http://groups-beta.google.com/group/comp.os.ms-windows.nt.misc/browse_frm/t…
>
>
>  here:
>
>  /
>  // MessageId: *THREAD_TERMINATE_HELD_MUTEX*
>  //
>  // MessageText:
>  //
>  //  A kernel thread terminated while holding a mutex
>  //
>
>  Best regards,
>  Alex Ionescu
>  
Exist there a way to check, if the mutex is only used in user mode? A
user mode thread can create and lock a mutex. An other thread terminates
this thraed and ros does crash.

- Hartmut

[Alex Ionescu]

Hartmut Birr wrote:

>  Exist there a way to check, if the mutex is only used
> in user mode? A
> user mode thread can create and lock a mutex. An other thread terminates
> this thraed and ros does crash.
>
> - Hartmut
>
>   
>  
Hi,

How can a user-mode thread create a mutex?

Best regards,
Alex Ionescu

[Hartmut Birr]

Alex Ionescu wrote:

>  
>  How can a user-mode thread create a mutex? 
Simply with CreateMutex. I change the assert statement to:

ASSERT(Mutant->Header.Size == sizeof(KMUTANT)/sizeof(ULONG));

This does ros crash only for mutex objects and not for mutant objects.

- Hartmut

[Alex Ionescu]

Hartmut Birr wrote:

>  Alex Ionescu wrote:
>
>   
>
> >  How can a user-mode thread create a mutex?
> >     
> >  
> Simply with CreateMutex. 
>  
CreateMutex creates a Mutant....

>  I change the assert statement to:
>
> ASSERT(Mutant->Header.Size == sizeof(KMUTANT)/sizeof(ULONG));
>
> This does ros crash only for mutex objects and not for mutant objects.
>   
>  
That's what the assert should do as well. Mutants have APC Disable = 0. 
Mutexes have it =1. Usermode can only create mutant, so apcdisable will 
always be 0.

I don't understand how user-mode can create a mutex?

>  - Hartmut
>   
>  
Best regards,
Alex Ionescu

[Hartmut Birr]

Alex Ionescu wrote:

>   That's what the assert should do as well. Mutants
> have APC Disable =
>  0. Mutexes have it =1. Usermode can only create mutant, so apcdisable
>  will always be 0. 
This means the ASSERT statemant is wrong. The correct statement is:

ASSERT(Mutant->ApcDisable == 0);

- Hartmut

[Alex Ionescu]

Hartmut Birr wrote:

>  Alex Ionescu wrote:
>
>   
>
> >  That's what the assert should do as well.
> > Mutants have APC Disable =
> > 0. Mutexes have it =1. Usermode can only create mutant, so apcdisable
> > will always be 0.
> >     
> >  
> This means the ASSERT statemant is wrong. The correct statement is:
>
> ASSERT(Mutant->ApcDisable == 0);
>
> - Hartmut
>   
>  
Hi,

Right, sorry for not seeing this! Can you please fix it, my kthread.c is 
completely modified due to my local scheduler rewrite.
Thank you!

Best regards,
Alex Ionescu