Guarded mutex

[Aliberti Emanuele]

I found a note, in Kernel Mustard's (Steve Dispensa) blog, about guarded
mutexes, which is a completely new synchronization object to me.
typedef struct _KGUARDED_MUTEX
  ULONG     Count;
  PKTHREAD  Owner;
  ULONG     Contention;
  KGATE     Gate;
  WORD      KernelApcDisable;
  WORD      SpecialApcDisable;
  ULONG     CombinedApcDisable;
} KGUARDED_MUTEX, *PKGUARDED_MUTEX;
What are they? KM says they are less expensive than FAST_MUTEXes.
By the way, what is a KGATE?
Emanuele

[Filip Navara]

Aliberti Emanuele wrote:
>   What are they? KM says they are less expensive than
> FAST_MUTEXes. 
They're similar to fast mutexes, but do not block APCs by raising IRQL
to APC_LEVEL. Instead they just enter critical section (called Guarded
Region).

[Alex Ionescu]

Filip Navara wrote:
>   Aliberti Emanuele wrote:
> >   What are they? KM says they are less expensive
> > than FAST_MUTEXes. 
>  They're similar to fast mutexes, but do not block APCs by raising IRQL
>  to APC_LEVEL. Instead they just enter critical section (called Guarded
>  Region).
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They are also talked about in the Syncronization PDFs, on page 45.
Gates are a stripped-down Dispatcher Object, which are very similar to
Events. They can only be initialized and waited on. They also have
Priorities and Boosts that can be applied to them. (Once again, just
like Events).
Best regards,
Alex Ionescu