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 glibc 2.24.
This patch makes a distinction in the manual page between glibc 2.24 and
older versions.
Upstream commit in glibc.git:
9ff72da471 posix: New Linux posix_spawn{p} implementation
Signed-off-by: Olivier Gayot <olivier.gayot@xxxxxxxxxxx>
---
man3/posix_spawn.3 | 26 ++++++++++++++++++--------
1 file changed, 18 insertions(+), 8 deletions(-)
diff --git a/man3/posix_spawn.3 b/man3/posix_spawn.3
index 3e1e9011c..e8c0de172 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)
@@ -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
@@ -527,13 +536,14 @@ only the POSIX-specified functions.
although these objects may be implemented as structures containing fields,
portable programs must avoid dependence on such implementation details.)
.PP
-According to POSIX, it unspecified whether fork handlers established with
+According to POSIX, it is unspecified whether fork handlers established with
.BR pthread_atfork (3)
are called when
.BR posix_spawn ()
is invoked.
-On glibc,
+Since glibc 2.24, the fork handlers are not executed in any case.
.\" Tested on glibc 2.12
+On older implementations,
fork handlers are called only if the child is created using
.BR fork (2).
.PP
--
2.19.1
