No sweat. You added to the conversation that might eventually generate an
answer. To me it’s a function that is needed, but then maybe I’m the only
one that needs to remove entries in the middle of the list.
Gary
-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com] On Behalf Of Michael Jackson
Sent: Friday, July 06, 2001 10:39 AM
To: NT Developers Interest List
Subject: [ntdev] RE: [NTDEV] Queue Management …
Gary:
Nope, I wasn’t.
I was saying that I was also puzzled that the set of list functions was
incomplete and at the time my guess as to why they were incomplete was that
they weren’t created for our (the developer community outside of M$) use,
but for some task the OS developers needed done. They didn’t need to act on
entries in the middle of the list. Then the list functions that were
generated, were exposed for our use.
This was just a guess. Sorry if I added to the confusion.
Michael J.
-----Original Message-----
From: Gary Little [mailto:xxxxx@Broadstor.com]
Sent: Thursday, July 05, 2001 1:24 PM
To: NT Developers Interest List
Subject: [ntdev] RE: [NTDEV] Queue Management …
Michael,
I’m a bit confused … which my wife says is common at my age.
Are you implying that you, or a group you were associated with, were
responsible for the development of the ExIntelocked… list functions?
Gary G. Little
Staff Engineer
Broadband Storage, Inc.
xxxxx@broadstor.com
-----Original Message-----
From: Michael Jackson [mailto:xxxxx@nmwco.com]
Sent: Thursday, July 05, 2001 12:41 PM
To: NT Developers Interest List
Subject: [ntdev] RE: [NTDEV] Queue Management …
Gary:
When I saw this I assumed that this was just implemented for a particular
task and it didn’t involve operating on the middle of the list. Nobody was
given the task of creating a “full” set of list operators.
Are we having fun yet?
Michael S. Jackson
xxxxx@netmotionwireless.com
-----Original Message-----
From: Gary Little [mailto:xxxxx@Broadstor.com]
Sent: Tuesday, July 03, 2001 10:50 AM
To: NT Developers Interest List
Subject: [ntdev] [NTDEV] Queue Management …
In prior versions of the DDK, there has never been an interlocked mid-queue
management function. You can insert on the tail or head using
ExInterlockedInsertTail/HeadList, or remove from the tail or head using
ExInterlockedRemoveTail/HeadList. However, the only way to remove things
from the middle of a queue was RemoveEntryList, which is but one of those
deadly macros.
Why has there never been an ExInterlockedRemoveEntryList to permit an
orthogonal, and atomic, management of doubly linked queues? For my own
purposes I have written one using a combination of inline assembly to clear
and restore the interrupt mask “pushfd/cli/…popfd”, and “lock bts” to
acquire a spin lock, and RemoveEntryList to manage the queue. However, it
would be nice if this were down in the HAL, or kernel, to provide some
platform independence and total synchronized queue management.
I posted this in the DDK Beta newsgroup for XP and received the following
reply from a Jamie Hunter at Microsoft:
“Disabling and enabling the interrupts on NT code base is bad! For starters,
it will not be mutually exclusive in multi-processor systems, so the
behavior you expect isn’t what you get, and this kind of thing makes drivers
unstable on multi-proc when working fine on single-proc. ExInterlockedXXX
APIs use processor instructions that are guaranteed to be exclusive on a
multi-processor system. Depending on what you need to be exclusive with, you
should use spin-locks or KeSynchronizeExecution.”
The fact that the ExInterlockedXXX functions use “pushfd/cli/…popfd”, and
“lock bts” to acquire a spin lock tends to make the remainder of Jamie’s
argument moot. I simply think they need to add one more. Spin locks will not
solve my particular problem since the queue I am managing must be accessed
at IRQLs above DISPATCH_LEVEL. I cannot use KeSynchronizeExecution because
my design is such that queue management is carried out in a layer where I do
not have access to the interrupt object. Without
ExInterlockedRemoveEntryList, management of that queue between
DISPATCH_LEVEL and DIRQL becomes a real problem.
My question is, since interlocked functions exist for Insert/Remove
head/tail of a list, why not mid-queue management as well?
Gary G. Little
Staff Engineer
Broadband Storage, Inc.
xxxxx@broadstor.com
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