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    SubjectRe: [PATCH, RFC 1/3] Add sem_getcount() to arches that lack it
    On Fri, Mar 11, 2005 at 12:27:47PM +0000, Matthew Wilcox wrote:

    > > But I guess it's a bit hard to justify adding more infrastructure to
    > > support a single callsite which has a simple alternative. So if you could
    > > please add the separate counter?
    > It's pretty *small* infrastructure, and it gives me something to whine at
    > people about when they use atomic_read on something that isn't an atomic.

    Agreed, but I don't mind adding a separate counter. However...

    > If we are going to get rid of sem_getcount, could we rename the 'count'
    > variables, at least on i386 and ppc to make it clear that you're not
    > supposed to do this ... maybe to 'count_$ARCH'?

    I'm working on a patch to do just that. It fails when building XFS:

    fs/xfs/xfs_inode_item.c: In function `xfs_inode_item_pushbuf':
    fs/xfs/xfs_inode_item.c:803: error: structure has no member named `count'
    fs/xfs/xfs_inode_item.c:825: error: structure has no member named `count'

    #define valusema(sp) (atomic_read(&(sp)->count))

    It seems getting the value of a semaphore is more common than it appears
    at first glance. I don't see how this code could possibly work on
    parisc. Therefore I propose:

    1. Adding sem_getcount() everywhere, as in my original patch.
    2. Renaming count to count_$ARCH as willy suggested.
    3. Anyone who abuses semaphores will now break. Fix them to use

    I'll work on that over the weekend unless anyone has any better ideas.


    > --
    > "Next the statesmen will invent cheap lies, putting the blame upon
    > the nation that is attacked, and every man will be glad of those
    > conscience-soothing falsities, and will diligently study them, and refuse
    > to examine any refutations of them; and thus he will by and by convince
    > himself that the war is just, and will thank God for the better sleep
    > he enjoys after this process of grotesque self-deception." -- Mark Twain

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