Re: [tip:core/signals] signals/sigaltstack: Prepare to add new SS_xxx flags

[Andy Lutomirski]

On Tue, May 3, 2016 at 12:50 AM, tip-bot for Stas Sergeev
<tipbot@xxxxxxxxx> wrote:
> Commit-ID:  407bc16ad1769f5cb8ad9555611cb198187ef4cd
> Gitweb:     http://git.kernel.org/tip/407bc16ad1769f5cb8ad9555611cb198187ef4cd
> Author:     Stas Sergeev <stsp@xxxxxxx>
> AuthorDate: Thu, 14 Apr 2016 23:20:03 +0300
> Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
> CommitDate: Tue, 3 May 2016 08:37:59 +0200
>
> signals/sigaltstack: Prepare to add new SS_xxx flags
>
> This patch adds SS_FLAG_BITS - the mask that splits sigaltstack
> mode values and bit-flags. Since there is no bit-flags yet, the
> mask is defined to 0. The flags are added by subsequent patches.
> With every new flag, the mask should have the appropriate bit cleared.
>
> This makes sure if some flag is tried on a kernel that doesn't
> support it, the -EINVAL error will be returned, because such a
> flag will be treated as an invalid mode rather than the bit-flag.
>
> That way the existence of the particular features can be probed
> at run-time.
>
> This change was suggested by Andy Lutomirski:
>
>   https://lkml.org/lkml/2016/3/6/158

LGTM.