Messages in this thread | | | Date | Fri, 10 May 2002 14:48:39 -0700 | From | Dave Hansen <> | Subject | fs/locks.c BKL removal |
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Matthew, Al Viro pointed me your way.
I'm looking into the fs/locks.c mess. It appears that there was an attempt to convert this over to a semaphore, but it was removed just before the 2.4 release because of some deadlocks.
Whenever the i_flock list is traversed, the BKL is held. It is also held while running through the file_lock_list which I think is used only for /proc/locks.
We definitely need a semaphore because of all the blocking that goes on. We can either have a global lock for all of them, which I think was tried last time. Or, we can split it up a bit more. With the current design, there will need to be a lock for the global list, each individual list, and one for each individual lock to protect against access from the reference in the file_lock_list and the inode->i_flock list.
However, I think that the file_lock_list complexity may be able to be reduced. If we make the file_lock_list a list of inodes (or just the i_flocks) with active locks, we can avoid the complexity of having an individual file_lock lock. That way, we at least reduce the number of _types_ of locks. It increases the number of dereferences, but this is /proc we're talking about. Any comments?
Talking about locks for locks is confusing :)
-- Dave Hansen haveblue@us.ibm.com
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