Messages in this thread | | | Date | Thu, 23 May 2013 16:20:27 +0200 | From | Lars-Peter Clausen <> | Subject | Re: [PATCH 2/2] regmap: Make regmap-mmio usable from different contexts |
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On 05/23/2013 04:05 PM, Mark Brown wrote: > On Thu, May 23, 2013 at 03:06:16PM +0200, Lars-Peter Clausen wrote: > >> This patch updates the adds a flags parameter to the regmap lock and unlock >> callbacks and uses spin_lock_irqsave() and spin_unlock_restore() for the mmio >> case. This allows us to use regmap-mmio from different contexts. > > This seems really invasive, why not just have the lock that gets passed > in point to a struct which has both the lock and the flags? As far as > the core is concerned the lock is just whatever data is required to do > the locking, the fact that it's actually two values is an implementation > detail of this locking implementation.
I think that won't work. spin_lock_irqsave() will write to the flags parameter before it has successfully taken the look. So if a process running on another CPU tries to acquire the the lock while it is already held we'll end up overwriting the flags. E.g:
CPU0 CPU1 spin_lock_irqsave() - write flags
spin_lock_irqsave() - overwrite flags
spin_unlock_irqrestore() - restore wrong flags
Hence flags needs to go onto the stack.
- Lars
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