Re: [PATCH] poll.2/select.2: Add a reference to the sigset discussion in sigprocmask

["Michael Kerrisk (man-pages)" <mtk.manpages-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

Hello Keno,

On 12/27/2016 08:32 PM, Keno Fischer wrote:
> A little while back, I added a note to sigprocmask.2 that discussed the
> difference between the libc's and the kernel's sigset_t structures.
> I added that note, because I saw this being done wrong in a tool tracing
> system calls (causing subtle bugs). As it turns out, the same bugs existed
> for ppoll and pselect, for the same reason. I'm hoping by adding the
> reference here, future writers of similar tools will find that discussion
> and not make the same mistake.

Thanks! Applied.

Cheers,

Michael

> ---
>  man2/poll.2   |  5 ++++-
>  man2/select.2 | 11 +++++++----
>  2 files changed, 11 insertions(+), 5 deletions(-)
> 
> diff --git a/man2/poll.2 b/man2/poll.2
> index 26bb10d..163df6e 100644
> --- a/man2/poll.2
> +++ b/man2/poll.2
> @@ -416,7 +416,10 @@ The glibc
>  .BR ppoll ()
>  wrapper function specifies this argument as a fixed value
>  (equal to
> -.IR sizeof(sigset_t) ).
> +.IR sizeof(kernel_sigset_t) ). See
> +.BR sigprocmask(2)
> +for a discussion on the differences between the kernel and the libc
> +notion of the sigset.
>  .SH BUGS
>  See the discussion of spurious readiness notifications under the
>  BUGS section of
> diff --git a/man2/select.2 b/man2/select.2
> index 1a5d36a..5b02fda 100644
> --- a/man2/select.2
> +++ b/man2/select.2
> @@ -510,9 +510,9 @@ pointer, but is instead a structure of the form:
>  .nf
>  
>  struct {
> -    const sigset_t *ss;     /* Pointer to signal set */
> -    size_t          ss_len; /* Size (in bytes) of object pointed
> -                               to by 'ss' */
> +    const kernel_sigset_t *ss;     /* Pointer to signal set */
> +    size_t                 ss_len; /* Size (in bytes) of object pointed
> +                                      to by 'ss' */
>  };
>  
>  .fi
> @@ -520,7 +520,10 @@ struct {
>  This allows the system call to obtain both
>  a pointer to the signal set and its size,
>  while allowing for the fact that most architectures
> -support a maximum of 6 arguments to a system call.
> +support a maximum of 6 arguments to a system call. See
> +.BR sigprocmask(2)
> +for a discussion of the difference between the kernel and libc
> +notion of the signal set.
>  .SH BUGS
>  POSIX allows an implementation to define an upper limit,
>  advertised via the constant
> 


-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
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