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    Subject[PATCH] _raw_read_trylock for alpha

    alpha SMP doesn't build, due to lack of _raw_read_trylock().

    Patch below completely untested... needs review and testing.

    One could also use the arch-neutral generic_raw_read_trylock(),
    but that implementation is rather lame (it spins). I'm amazed at the
    number of arches that use the generic implementation, since the generic
    version isn't really a "trylock".

    Don't send this patch upstream until its been verified to actually work.

    Signed-off-by: Jeff Garzik <jgarzik@pobox.com>


    diff -ur ../kernel-2.6.11.orig/linux-2.6.11/include/asm-alpha/spinlock.h linux-2.6.11/include/asm-alpha/spinlock.h
    --- ../kernel-2.6.11.orig/linux-2.6.11/include/asm-alpha/spinlock.h 2005-03-02 02:38:12.000000000 -0500
    +++ linux-2.6.11/include/asm-alpha/spinlock.h 2005-03-19 03:26:11.000000000 -0500
    @@ -153,6 +153,29 @@
    }
    #endif /* CONFIG_DEBUG_RWLOCK */

    +static inline int _raw_read_trylock(rwlock_t * lock)
    +{
    + long regx;
    + int success;
    +
    + __asm__ __volatile__(
    + "1: ldl_l %1,%0\n"
    + " lda %2,0\n"
    + " blbs %1,6f\n"
    + " subl %1,2,%1\n"
    + " stl_c %1,%0\n"
    + " beq %1,6f\n"
    + " lda %2,1\n"
    + "4: mb\n"
    + ".subsection 2\n"
    + "6: br 1b\n"
    + ".previous"
    + : "=m" (*lock), "=&r" (regx), "=&r" (success)
    + : "m" (*lock) : "memory");
    +
    + return success;
    +}
    +
    static inline int _raw_write_trylock(rwlock_t * lock)
    {
    long regx;
    -
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