On 15/10/2018 17:01, Olivier Gayot wrote:
> Since glibc 2.24, the use of posix_spawn (2) makes an unconditional call
> to clone(CLONE_VM | CLONE_VFORK ...) rather than relying on fork (2) or
> vfork (2).
>
> As a consequence, the statements regarding the use of the flag
> POSIX_SPAWN_USEVFORK and how the function decides whether it should use
> fork (2) or vfork (2) are obsolete since this glibc 2.24.
>
> This patch makes a distinction in the manual page between glibc 2.24 and
> older versions.
Thanks for following this up. Since you updating posix_spawn{p} documentation
I think it is worth to mention that POSIX_SPAWN_SETSID has been accepted by
POSIX [1] and it has been implemented on glibc since 2.26 (daeb1fa2e1b33).
[1] http://austingroupbugs.net/view.php?id=1044
>
> Upstream commit in glibc.git:
>
> 9ff72da471 posix: New Linux posix_spawn{p} implementation
Should we make explicit that for glibc 2.24+ POSIX_SPAWN_USEVFORK is a noop?
>
> Signed-off-by: Olivier Gayot <olivier.gayot@xxxxxxxxxxx>
> ---
> man3/posix_spawn.3 | 21 +++++++++++++++------
> 1 file changed, 15 insertions(+), 6 deletions(-)
>
> diff --git a/man3/posix_spawn.3 b/man3/posix_spawn.3
> index 3e1e9011c..9cc5a63d5 100644
> --- a/man3/posix_spawn.3
> +++ b/man3/posix_spawn.3
> @@ -155,9 +155,16 @@ and the
> .BR exec ()
> step (executed in the child).
> .SS fork() step
> -The
> +Since glibc 2.24, the
> .BR posix_spawn ()
> function commences by calling
> +.BR clone (2)
> +with
> +.BR CLONE_VM
> +and
> +.BR CLONE_VFORK
> +flags.
> +Older implementations use
> .BR fork (2),
> or possibly
> .BR vfork (2)
Although there is a note below that atfork handlers are only executed if
posix_spawn{p} use fork, maybe make explicit that for GLIBC 2.24 they
won't be execute in any case?
> @@ -176,7 +183,7 @@ If the child fails in any of the housekeeping steps described below,
> or fails to execute the desired file,
> it exits with a status of 127.
> .PP
> -The child process is created using
> +Before glibc 2.24, the child process is created using
> .BR vfork (2)
> instead of
> .BR fork (2)
> @@ -480,14 +487,16 @@ The
> and
> .BR posix_spawnp ()
> functions fail only in the case where the underlying
> -.BR fork (2)
> -or
> +.BR fork (2),
> .BR vfork (2)
> +or
> +.BR clone (2)
> call fails; in these cases, these functions return an error number,
> which will be one of the errors described for
> -.BR fork (2)
> +.BR fork (2),
> +.BR vfork (2)
> or
> -.BR vfork (2).
> +.BR clone (2).
> .PP
> In addition, these functions fail if:
> .TP
>
