Dispatch routine IRQL and thread Context

The following table summarizes the IRQL and thread context requirements for file system filter driver dispatch routines.

DriverEntry
Routines are called in the context of a system thread at IRQL = passive_level.

Most drivers 'dispatch routines are called in an arbitrary thread
Context at IRQL = passive_level, with the following exceptions:

• Any highest-level driver's dispatch routines
  Are called in the context of the thread that originated the I/O
  Request, which is commonly a user-mode application thread.

  In other words, the dispatch routines of file system drivers
  And other highest-level drivers are called in a nonarbitrary thread
  Context at IRQL = passive_level.

• TheDispatchread
  ,Dispatchwrite
  , AndDispatchdevicecontrol
  Routines of lowest-level device drivers, and of Intermediate Drivers
  Layered above them in the system paging path, can be called at IRQL =
  Apc_level and in an arbitrary thread context.

  TheDispatchread
  And/orDispatchwrite
  Routines, and any other routine that also processes read and/or write
  Requests in such a lowest-level device or intermediate driver,Must be resident at all times
  .These
  Driver routines can neither be pageable or be part of a driver's
  Pageable-image section; they must not access any pageable memory
  . Furthermore, they shoshould not be dependent on any blocking CALS (suchKewaitforsingleobject
  With a nonzero time-out ).

• TheDispatchpower
  Routine of drivers in the hibernation and/or paging paths can be called at IRQL = dispatch_level.Dispatchpnp
  Routines of such drivers must be prepared to handle PNP irp_mn_device_usage_notification requests.
• TheDispatchpower
  Routine of drivers that require inrush power at start-up can be called at IRQL = dispatch_level.

 

Dispatch routine	Caller's IRQL:	Caller's thread context:
Cleanup	Passive_level	Nonarbitrary
Close	Apc_level	Arbitrary
Create	Passive_level	Nonarbitrary
Devicecontrol (Cipher t paging I/O)	Passive_level	Nonarbitrary
Devicecontrol (paging I/O path)	Apc_level	Arbitrary
Directorycontrol	Apc_level	Arbitrary
Flushbuffers	Passive_level	Nonarbitrary
Fscontrol (generation T paging I/O)	Passive_level	Nonarbitrary
Fscontrol (paging I/O path)	Apc_level	Arbitrary
Lockcontrol	Passive_level	Nonarbitrary
PNP	Passive_level	Arbitrary
Queryea	Passive_level	Nonarbitrary
Queryinformation	Passive_level	Nonarbitrary
Queryquota	Passive_level	Nonarbitrary
Querysecurity	Passive_level	Nonarbitrary
Queryvolumeinfo	Passive_level	Nonarbitrary
Read (partition t paging I/O)	Passive_level	Nonarbitrary
Read (paging I/O path)	Apc_level	Arbitrary
Setea	Passive_level	Nonarbitrary
Setinformation	Passive_level	Nonarbitrary
Setquota	Passive_level	Nonarbitrary
Setsecurity	Passive_level	Nonarbitrary
Setvolumeinfo	Passive_level	Nonarbitrary
Shutdown	Apc_level	Arbitrary
Write (writable t paging I/O)	Passive_level	Nonarbitrary
Write (paging I/O path)	Apc_level	Arbitrary