On Wed, Jan 16, 2013 at 11:57 AM, Ralf Baechle <ralf@xxxxxxxxxxxxxx> wrote:
> On Mon, Jan 14, 2013 at 10:47:03PM +0100, Cong Ding wrote:
>
>> the variable dummy is used without initialization.
>
> Interesting - I wonder how you found this one. My compiler (gcc 4.7)
> doesn't warn about this one.
Probably older gcc does.
> Nor does gcc notice that the whole summing up business is wasted efford.
>
> So here's my counter proposal. It works because ptr is a volatile pointer
> so the compiler will always dereference it even if the returned value is
> not being used. The resulting code is a bit smaller.
>
> Ralf
>
> Signed-off-by: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
>
> arch/mips/cavium-octeon/executive/cvmx-l2c.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/mips/cavium-octeon/executive/cvmx-l2c.c b/arch/mips/cavium-octeon/executive/cvmx-l2c.c
> index 9f883bf..ec3e059 100644
> --- a/arch/mips/cavium-octeon/executive/cvmx-l2c.c
> +++ b/arch/mips/cavium-octeon/executive/cvmx-l2c.c
> @@ -286,7 +286,7 @@ uint64_t cvmx_l2c_read_perf(uint32_t counter)
> static void fault_in(uint64_t addr, int len)
> {
> volatile char *ptr;
> - volatile char dummy;
> +
> /*
> * Adjust addr and length so we get all cache lines even for
> * small ranges spanning two cache lines.
> @@ -300,7 +300,7 @@ static void fault_in(uint64_t addr, int len)
> */
> CVMX_DCACHE_INVALIDATE;
> while (len > 0) {
> - dummy += *ptr;
> + *ptr;
Alternatively, to make clearer what's intended:
- drop the "volatile" from "ptr" and from the cast when assigning to it,
- use "ACCESS_ONCE(*ptr)" instead of "*ptr".
> len -= CVMX_CACHE_LINE_SIZE;
> ptr += CVMX_CACHE_LINE_SIZE;
> }
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
