[PATCH] Removal of big kernel lock from isdn drivers

[PATCH] Removal of big kernel lock from isdn drivers

[Dave Hansen]

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