lkml.org 
[lkml]   [2014]   [Feb]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCH] regmap: don't use spinlocks with REGCACHE_{RBTREE,COMPRESSED}
From
On Thu, Feb 27, 2014 at 3:37 AM, Mark Brown <broonie@kernel.org> wrote:
> On Wed, Feb 26, 2014 at 07:50:57PM -0800, Andrew Bresticker wrote:
>> Both REGCACHE_RBTREE and REGCACHE_COMPRESSED make GFP_KERNEL allocations
>> with the regmap lock held. If we're initializing a regmap which would
>> normally use a spinlock (e.g. MMIO), fall back to using a mutex if one
>> of these caching types is to be used.
>
> Have all the users been audited to verify that they're actually safe
> with this? I just took a quick look at the Tegra drivers and they're
> doing regmap operations in their trigger operations which is done from
> atomic context so they should run into problems trying to take mutexes
> anyway.

Oops, you're right, I didn't look through all the regmap operations
carefully enough. It is in fact the Tegra drivers I've ran into this
issue with.

> I think we need to either ensure that all users allocate their caches at
> probe time (which is fine and is hopefully what the current users are
> doing), provide a mechanism for them to do cache allocations outside of
> the spinlock (which sounds hairy) or convert them to flat cache.

Allocations are made in the write path for rbtree and in both the read
and write paths for lzo. I suppose we can pre-allocate everything at
init time, but I haven't looked too much at that. For at least the
Tegra drivers, the best option for now appears to be to convert to a
flat cache.

Thanks,
Andrew


\
 
 \ /
  Last update: 2014-02-28 04:01    [W:0.902 / U:0.316 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site