On Fri, Apr 17 2015, Mathieu Desnoyers <mathieu.desnoy...@efficios.com> wrote:
> + */
> +SYSCALL_DEFINE2(membarrier, int, cmd, int, flags)
> +{
> + switch (cmd) {
> + case MEMBARRIER_CMD_QUERY:
> + return MEMBARRIER_CMD_BITMASK;
> + case MEMBARRIER_CMD_SHARED:
> + if (num_online_cpus() > 1)
> + synchronize_sched();
> + return 0;
> + default:
> + return -EINVAL;
> + }
> +}
Shouldn't flags be enforced 0, to actually make future extensions
possible without risk of breaking some sloppy userspace? I think that is
or should be part of "make sure new syscalls take a flags parameter".
> + * If this system call is not implemented, -ENOSYS is returned. If the
> + * command specified does not exist, or if the command argument is invalid,
> + * this system call returns -EINVAL. For a given command, this system call
> + * is guaranteed to always return the same value until reboot.
I like that guarantee, but it may be a bit much to promise for any and
all possible future flags. So maybe weaken it to 'For a given command
and flags==0, this ...'.
Rasmus
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