Messages in this thread | | | Date | Fri, 26 Oct 2012 12:09:41 -0400 (EDT) | From | Mikulas Patocka <> | Subject | Re: [PATCH 1/2] brw_mutex: big read-write mutex |
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On Fri, 26 Oct 2012, Oleg Nesterov wrote:
> > The code is different, but it can be changed to use percpu rw semaphores > > (if we add percpu_down_write_trylock). > > I don't really understand how you can make percpu_down_write_trylock() > atomic so that it can be called under br_write_lock(vfsmount_lock) in > sb_prepare_remount_readonly(). So I guess you also need to replace > vfsmount_lock at least. Or _trylock needs the barriers in _down_read. > Or I missed something. > > Oleg.
That's true - that code is under spinlock and you can't implement non-blocking percpu_down_write_trylock.
Mikulas
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