On Fri, Jun 05, 2015 at 11:08:57PM +0200, Oleg Nesterov wrote: > On 06/05, Al Viro wrote: > > > > FWIW, I hadn't really looked into stop_machine uses, but fs/locks.c one > > is really not all that great - there we have a large trashcan of a list > > (every file_lock on the system) and the only use of that list is /proc/locks > > output generation. Sure, additions take this CPU's spinlock. And removals > > take pretty much a random one - losing the timeslice and regaining it on > > a different CPU is quite likely with the uses there. > > > > Why do we need a global lock there, anyway? Why not hold only one for > > the chain currently being traversed? Sure, we'll need to get and drop > > them in ->next() that way; so what? > > And note that fs/seq_file.c:seq_hlist_next_percpu() has no other users. > > And given that locks_delete_global_locks() takes the random lock anyway, > perhaps the hashed lists/locking makes no sense, I dunno.
It's not about making life easier for /proc/locks; it's about not screwing those who add/remove file_lock... And no, that "random lock" isn't held when modifying the (per-cpu) lists - it protects the list hanging off each element of the global list, and /proc/locks scans those lists, so rather than taking/dropping it in each ->show(), it's taken once in ->start()... -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
