Messages in this thread |  | | | Date | Thu, 23 Apr 2009 12:07:10 +0300 | | From | Benny Halevy <> | | Subject | Re: [RFC] __ffs64() |
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On Apr. 23, 2009, 11:22 +0300, Steven Whitehouse <swhiteho@redhat.com> wrote: > Hi, > > On Wed, 2009-04-22 at 16:59 -0400, Christoph Lameter wrote: >> On Wed, 22 Apr 2009, Steven Whitehouse wrote: >> >>> I'd like to add a new bitop, __ffs64() which I need in order to fix a >>> bug in GFS2. The question is, where should it go? >> I think the location is right. >> >>> On 64 bit arches, __ffs64() would be a synonym for __ffs(), but on 32 >>> bit arches it degenerates to a conditional plus a call to __ffs(). I'm >>> assuming that there would not be a lot of point in optimising this >>> operation on 32 bit arches even if such an instruction was available, so >>> that I should do something like the below patch. >>> >>> Does that seem reasonable, or should I give it a separate header file >>> under asm-generic/bitops/ like some of the similar operations? It looks >>> like I'd have to touch a lot of other files if I were to go that route, >> One issue may be that some 32 bit architectures have a better way of doing >> 64 bit ffs. >> > Yes, thats what I was worried about. I don't have a wide enough > knowledge of the different architectures to make a judgement about > whether this is likely or not. > > I guess maybe the right thing to do is to leave it as I did it in the > patch and if an arch wants to create its own implementation, then it > could be moved at that stage.
Agreed.
Benny
> > Steve. > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/
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