Messages in this thread | | | Date | Fri, 13 Jan 2006 16:19:34 +0100 | From | Adrian Bunk <> | Subject | Re: [PATCH 1 of 3] Introduce __raw_memcpy_toio32 |
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On Tue, Jan 10, 2006 at 03:32:57PM -0800, Andrew Morton wrote: > "Bryan O'Sullivan" <bos@pathscale.com> wrote: > > > > On Tue, 2006-01-10 at 14:05 -0800, Andrew Morton wrote: > > > > > It's kinda fun playing Brian along like this ;) > > > > A regular barrel of monkeys, indeed... > > > > > One option is to just stick the thing in an existing lib/ or kernel/ file > > > and mark it __attribute__((weak)). That way architectures can override it > > > for free with no ifdefs, no Makefile trickery, no Kconfig trickery, etc. > > > > I'm easy. Would you prefer to take that, or the Kconfig-trickery-based > > patch series I already posted earlier? > > > > Unless someone can think of a problem with attribute(weak), I think you'll > find that it's the simplest-by-far solution.
__attribute__((weak)) can turn compile error into runtime errors - you won't notice at compile time if it was forgotten to compile the non-weak version into the kernel (e.g. due to a typo in the Makefile).
Patch 05/17 from the 2.6.15.1 patchset contains a fix for such a bug present in 2.6.15.
A variation of this problem can occur in cases like __raw_memcpy_toio32 if it was forgotten to compile the non-weak version into the kernel and the kernel therefore uses the non-optimized version. That's not fatal, but it might take years until someone notices that there might be a few percent of performance missing.
cu Adrian
--
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