Messages in this thread | ![/](/images/icornerl.gif) | | Date | Sat, 30 Dec 2006 17:08:53 -0500 (EST) | From | "Robert P. J. Day" <> | Subject | Re: replace "memset(...,0,PAGE_SIZE)" calls with "clear_page()"? |
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On Sat, 30 Dec 2006, Denis Vlasenko wrote:
> On Friday 29 December 2006 07:16, Robert P. J. Day wrote: > > > > is there some reason there are so many calls of the form > > > > memset(addr, 0, PAGE_SIZE) > > > > rather than the apparently equivalent invocation of > > > > clear_page(addr) > > > > the majority of architectures appear to define the clear_page() > > macro in their include/<arch>/page.h header file, but not entirely > > identically, and in some cases that definition is conditional, as > > with i386: > > > > ============================================================= > > #ifdef CONFIG_X86_USE_3DNOW > > ... > > #define clear_page(page) mmx_clear_page((void *)(page)) > > ... > > #else > > ... > > #define clear_page(page) memset((void *)(page), 0, PAGE_SIZE) > > ... > > #endif > > ============================================================ > > > > should it perhaps be part of the CodingStyle doc to use the > > clear_page() macro rather than an explicit call to memset()? > > (and should all architectures be required to define that macro?) > > clear_page assumes that given address is page aligned, I think. It > may fail if you feed it with misaligned region's address.
i don't see how that can be true, given that most of the definitions of the clear_page() macro are simply invocations of memset(). see for yourself:
$ grep -r "#define clear_page" include
my only point here was that lots of code seems to be calling memset() when it would be clearer to invoke clear_page(). but there's still something a bit curious happening here. i'll poke around a bit more before i ask, though.
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