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    Subject[PATCH 10/11] x86, rwsem: provide __down_write_killable
    Date
    From: Michal Hocko <mhocko@suse.com>

    which uses the same fast path as __down_write except it falls back to
    call_rwsem_down_write_failed_killable slow path and return -EINTR if
    killed. To prevent from code duplication extract the skeleton of
    __down_write into a helper macro which just takes the semaphore
    and the slow path function to be called.

    Signed-off-by: Michal Hocko <mhocko@suse.com>
    ---
    arch/x86/include/asm/rwsem.h | 41 ++++++++++++++++++++++++++++-------------
    arch/x86/lib/rwsem.S | 8 ++++++++
    2 files changed, 36 insertions(+), 13 deletions(-)

    diff --git a/arch/x86/include/asm/rwsem.h b/arch/x86/include/asm/rwsem.h
    index d79a218675bc..4c3d90dbe89a 100644
    --- a/arch/x86/include/asm/rwsem.h
    +++ b/arch/x86/include/asm/rwsem.h
    @@ -99,21 +99,36 @@ static inline int __down_read_trylock(struct rw_semaphore *sem)
    /*
    * lock for writing
    */
    +#define ____down_write(sem, slow_path) \
    +({ \
    + long tmp; \
    + struct rw_semaphore* ret = sem; \
    + asm volatile("# beginning down_write\n\t" \
    + LOCK_PREFIX " xadd %1,(%2)\n\t" \
    + /* adds 0xffff0001, returns the old value */ \
    + " test " __ASM_SEL(%w1,%k1) "," __ASM_SEL(%w1,%k1) "\n\t" \
    + /* was the active mask 0 before? */\
    + " jz 1f\n" \
    + " call " slow_path "\n" \
    + "1:\n" \
    + "# ending down_write" \
    + : "+m" (sem->count), "=d" (tmp), "+a" (ret) \
    + : "a" (sem), "1" (RWSEM_ACTIVE_WRITE_BIAS) \
    + : "memory", "cc"); \
    + ret; \
    +})
    +
    static inline void __down_write(struct rw_semaphore *sem)
    {
    - long tmp;
    - asm volatile("# beginning down_write\n\t"
    - LOCK_PREFIX " xadd %1,(%2)\n\t"
    - /* adds 0xffff0001, returns the old value */
    - " test " __ASM_SEL(%w1,%k1) "," __ASM_SEL(%w1,%k1) "\n\t"
    - /* was the active mask 0 before? */
    - " jz 1f\n"
    - " call call_rwsem_down_write_failed\n"
    - "1:\n"
    - "# ending down_write"
    - : "+m" (sem->count), "=d" (tmp)
    - : "a" (sem), "1" (RWSEM_ACTIVE_WRITE_BIAS)
    - : "memory", "cc");
    + ____down_write(sem, "call_rwsem_down_write_failed");
    +}
    +
    +static inline int __down_write_killable(struct rw_semaphore *sem)
    +{
    + if (IS_ERR(____down_write(sem, "call_rwsem_down_write_failed_killable")))
    + return -EINTR;
    +
    + return 0;
    }

    /*
    diff --git a/arch/x86/lib/rwsem.S b/arch/x86/lib/rwsem.S
    index 40027db99140..d1a1397e1fb3 100644
    --- a/arch/x86/lib/rwsem.S
    +++ b/arch/x86/lib/rwsem.S
    @@ -101,6 +101,14 @@ ENTRY(call_rwsem_down_write_failed)
    ret
    ENDPROC(call_rwsem_down_write_failed)

    +ENTRY(call_rwsem_down_write_failed_killable)
    + save_common_regs
    + movq %rax,%rdi
    + call rwsem_down_write_failed_killable
    + restore_common_regs
    + ret
    +ENDPROC(call_rwsem_down_write_failed_killable)
    +
    ENTRY(call_rwsem_wake)
    /* do nothing if still outstanding active readers */
    __ASM_HALF_SIZE(dec) %__ASM_HALF_REG(dx)
    --
    2.8.0.rc3
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