Le 27/09/2016 à 16:10, Rui Teng a écrit :
> From: Anton Blanchard <[email protected]>
>
> Pull in a version of Anton's null_syscall benchmark:
> http://ozlabs.org/~anton/junkcode/null_syscall.c
> Into tools/testing/selftests/powerpc/benchmarks.
>
> Suggested-by: Michael Ellerman <[email protected]>
> Signed-off-by: Anton Blanchard <[email protected]>
> Signed-off-by: Rui Teng <[email protected]>
> ---
> .../testing/selftests/powerpc/benchmarks/Makefile | 2 +-
> .../selftests/powerpc/benchmarks/null_syscall.c | 157 +++++++++++++++++++++
> 2 files changed, 158 insertions(+), 1 deletion(-)
> create mode 100644 tools/testing/selftests/powerpc/benchmarks/null_syscall.c
>
[...]
> +
> +static void do_null_syscall(unsigned long nr)
> +{
> + unsigned long i;
> +
> + for (i = 0; i < nr; i++)
> + getppid();
> +}
> +
Looks like getppid() performs a rcu_read_lock(). Is that what we want ?
Shouldn't we use getpid() instead for a lighter syscall ?
Christophe