At what IRQL does the thread created by PsCreateSystemThread() execute?

NTFSD
1

Hi!
I wanted to know whether a system thread created by PsCreateSystemThread executes at some specific IRQL or arbitrary IRQL.

2

> I wanted to know whether a system thread created by PsCreateSystemThread

executes at some specific IRQL or arbitrary IRQL.

PASSIVE_LEVEL

L.

3

It executes at whatever IRQL the code asks it to execute at. If your
question is “at what IRQL does it start execution” the answer is
“PASSIVE_LEVEL” (as Ladislav pointed out.)

Note that if you have a work item and your work routine is called it is
SUPPOSED to be called at PASSIVE_LEVEL with all APCs enabled, but in
fact I have seen (due to bugs in OTHER work items) cases where this is
not true (this is particularly problematic for APCs because normally the
OS only verifies that the APC index is zero when the threat terminates.
On the checked build it does it when it transitions from kernel to user
mode. Neither apply to system worker threads.)

In your own work routine, you can thus change the IRQL, perform whatever
operations you want but when you are done you are expected to clean up
and leave the thread at the correct IRQL and with APCs enabled.

Tony Mason
Consulting Partner
OSR Open Systems Resources, Inc.
http://www.osr.com

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Subject: [ntfsd] At what IRQL does the thread created by
PsCreateSystemThread() execute?

Hi!
I wanted to know whether a system thread created by PsCreateSystemThread
executes at some specific IRQL or arbitrary IRQL.

Questions? First check the IFS FAQ at
https://www.osronline.com/article.cfm?id=17

You are currently subscribed to ntfsd as: xxxxx@osr.com
To unsubscribe send a blank email to xxxxx@lists.osr.com

4

It starts at PASSIVE, then all depends upon the code it will execute.

Maxim Shatskih, Windows DDK MVP
StorageCraft Corporation
xxxxx@storagecraft.com
http://www.storagecraft.com

----- Original Message -----
From:
To: “Windows File Systems Devs Interest List”
Sent: Sunday, September 24, 2006 10:39 AM
Subject: [ntfsd] At what IRQL does the thread created by PsCreateSystemThread()
execute?

> Hi!
> I wanted to know whether a system thread created by PsCreateSystemThread
executes at some specific IRQL or arbitrary IRQL.
>
> —
> Questions? First check the IFS FAQ at
https://www.osronline.com/article.cfm?id=17
>
> You are currently subscribed to ntfsd as: xxxxx@storagecraft.com
> To unsubscribe send a blank email to xxxxx@lists.osr.com