Messages in this thread | | | Date | Tue, 9 Feb 2010 22:14:27 +0300 | From | Anton Vorontsov <> | Subject | Re: [PATCH 3/3] of/gpio: Introduce of_put_gpio(), add ref counting for OF GPIO chips |
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On Tue, Feb 09, 2010 at 10:28:15AM -0700, Grant Likely wrote: [...] > Rather than having a lock at the device tree data pointer level which > mixes usage with potentially many other drivers; wouldn't it make more > sense to use a mutex at the of_gc subsystem context?
I don't think so.
of_gc = np->data; lock(of_gc); (or lock(devtree)) <do something with of_gc>
doesn't provide us what we need, i.e. it doesn't guarantee that np->data (of_gc) is still alive.
And here:
lock(np->data); (or lock(devtree)) of_gc = np->data; lock(of_gc); <do something with of_gc>
The second lock becomes useless (unless you also refcount np->data usage and can drop the devtree/np->data lock, and grab some other kind of lock, e.g. mutex, but this is silly).
Thanks,
-- Anton Vorontsov email: cbouatmailru@gmail.com irc://irc.freenode.net/bd2
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