clone.2: Rework the discussion of the historical CLONE_PID for clarity

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

diff --git a/man2/clone.2 b/man2/clone.2
index 1d932c3b79a948897f2665600312b0ae9295eb43..48e3ed88ac81bfb7aa4854f1d9066a86cd053f69 100644 (file)
--- a/man2/clone.2
+++ b/man2/clone.2
@@ -519,17 +519,18 @@ The store operation completes before
 .BR clone ()
 returns control to user space.
 .TP
-.BR CLONE_PID " (obsolete)"
+.BR CLONE_PID " (Linux 2.0 to 2.5.15)"
 If
 .B CLONE_PID
 is set, the child process is created with the same process ID as
 the calling process.
 This is good for hacking the system, but otherwise
 of not much use.
-Since 2.3.21 this flag can be
+From Linux 2.3.21 onward, this flag could be
 specified only by the system boot process (PID 0).
-It disappeared in Linux 2.5.16.
-Since then, the kernel silently ignores it without error.
+The flag disappeared completely from the kernel sources in Linux 2.5.16.
+Since then, the kernel silently ignores this bit if it is specified in
+.IR flags .
 .TP
 .BR CLONE_PTRACE " (since Linux 2.2)"
 If
@@ -1130,6 +1131,7 @@ was specified by an unprivileged process (process without \fBCAP_SYS_ADMIN\fP).
 .B EPERM
 .B CLONE_PID
 was specified by a process other than process 0.
+(This error occurs only on Linux 2.5.15 and earlier.)
 .TP
 .B EPERM
 .BR CLONE_NEWUSER