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Subject[PATCH] Removal of big kernel lock from isdn drivers
I've been examining the continuing additions of the big kernel lock 
(BKL) to the 2.5 tree. I noticed that in 2.5.3, the ISDN subsystem
added the BKL to several places. In response to this, I have written
several patches to attempt removal of the BKL from the ISDN subsystem.
I have little knowledge of the drivers themselves, so I would like some
assistance from those of you who understand them better. I probably
have an over-simplified view of the code, so my patches may be too
simplistic. They're a bit big, so I've made them available here:
http://www.sr71.net/ibm/isdn/

isdn.bkl-remove.ippp_lock.patch:
http://www.sr71.net/ibm/isdn/isdn.bkl-remove.isdn_dev_sem.patch
added ippp_lock to ippp_struct
* It appeared that the BKL was being used to guard the file struct's
private data field, which is a ippp_struct. I added a semaphore to
that structure which can be locked instead of the BKL.

isdn.bkl-remove.hydsn_cards_sem.patch:
http://www.sr71.net/ibm/isdn/isdn.bkl-remove.hydsn_cards_sem.patch
adds rwsemaphore hydsn_cards_sem
* hydsn_cards_sem guards the card_root list. It is a read/write
semaphore which must be held for write when modifying the list.

isdn.bkl-remove.isdn_dev_rwsem.patch:
http://www.sr71.net/ibm/isdn/isdn.bkl-remove.ppp_lock.patch
* changes name of "dev" to "isdn_dev"
- If there are going to be global variables,
they can at least not have exceedingly generic
names like "dev"!
* adds global isdn_dev_rwsem
- isdn_dev_rwsem must be held when manipulating "isdn_dev"

I know that these patches should probably be separate, but this is
easier for me.

--
Dave Hansen
haveblue@us.ibm.com



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