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    Subject[PATCH 3.16 096/410] xtensa: fix futex_atomic_cmpxchg_inatomic
    3.16.57-rc1 review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Max Filippov <jcmvbkbc@gmail.com>

    commit ca47480921587ae30417dd234a9f79af188e3666 upstream.

    Return 0 if the operation was successful, not the userspace memory
    value. Check that userspace value equals passed oldval, not itself.
    Don't update *uval if the value wasn't read from userspace memory.

    This fixes process hang due to infinite loop in futex_lock_pi.
    It also fixes a bunch of glibc tests nptl/tst-mutexpi*.

    Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
    Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
    ---
    arch/xtensa/include/asm/futex.h | 23 ++++++++++-------------
    1 file changed, 10 insertions(+), 13 deletions(-)

    --- a/arch/xtensa/include/asm/futex.h
    +++ b/arch/xtensa/include/asm/futex.h
    @@ -109,7 +109,6 @@ futex_atomic_cmpxchg_inatomic(u32 *uval,
    u32 oldval, u32 newval)
    {
    int ret = 0;
    - u32 prev;

    if (!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))
    return -EFAULT;
    @@ -120,26 +119,24 @@ futex_atomic_cmpxchg_inatomic(u32 *uval,

    __asm__ __volatile__ (
    " # futex_atomic_cmpxchg_inatomic\n"
    - "1: l32i %1, %3, 0\n"
    - " mov %0, %5\n"
    - " wsr %1, scompare1\n"
    - "2: s32c1i %0, %3, 0\n"
    - "3:\n"
    + " wsr %5, scompare1\n"
    + "1: s32c1i %1, %4, 0\n"
    + " s32i %1, %6, 0\n"
    + "2:\n"
    " .section .fixup,\"ax\"\n"
    " .align 4\n"
    - "4: .long 3b\n"
    - "5: l32r %1, 4b\n"
    - " movi %0, %6\n"
    + "3: .long 2b\n"
    + "4: l32r %1, 3b\n"
    + " movi %0, %7\n"
    " jx %1\n"
    " .previous\n"
    " .section __ex_table,\"a\"\n"
    - " .long 1b,5b,2b,5b\n"
    + " .long 1b,4b\n"
    " .previous\n"
    - : "+r" (ret), "=&r" (prev), "+m" (*uaddr)
    - : "r" (uaddr), "r" (oldval), "r" (newval), "I" (-EFAULT)
    + : "+r" (ret), "+r" (newval), "+m" (*uaddr), "+m" (*uval)
    + : "r" (uaddr), "r" (oldval), "r" (uval), "I" (-EFAULT)
    : "memory");

    - *uval = prev;
    return ret;
    }

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