From 97d8f83cb734525f96992fd61e4f7323ab3d549c Mon Sep 17 00:00:00 2001 From: Andrew Morton Date: Sun, 15 Jul 2007 23:41:20 -0700 Subject: [PATCH] Add Documentation/sysctl/ctl_unnumbered.txt Poeple keep on adding new numbered sysctls, when they're supposed not to. Add a documentation file which explain why new sysctls should use CTL_UNNUMBERED. The next patch will sprinkle pointers to this throughout sysctl.c. Eric provided the text (thanks) Cc: "Eric W. Biederman" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/sysctl/ctl_unnumbered.txt | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) create mode 100644 Documentation/sysctl/ctl_unnumbered.txt diff --git a/Documentation/sysctl/ctl_unnumbered.txt b/Documentation/sysctl/ctl_unnumbered.txt new file mode 100644 index 000000000000..23003a8ea3e7 --- /dev/null +++ b/Documentation/sysctl/ctl_unnumbered.txt @@ -0,0 +1,22 @@ + +Except for a few extremely rare exceptions user space applications do not use +the binary sysctl interface. Instead everyone uses /proc/sys/... with +readable ascii names. + +Recently the kernel has started supporting setting the binary sysctl value to +CTL_UNNUMBERED so we no longer need to assign a binary sysctl path to allow +sysctls to show up in /proc/sys. + +Assigning binary sysctl numbers is an endless source of conflicts in sysctl.h, +breaking of the user space ABI (because of those conflicts), and maintenance +problems. A complete pass through all of the sysctl users revealed multiple +instances where the sysctl binary interface was broken and had gone undetected +for years. + +So please do not add new binary sysctl numbers. They are unneeded and +problematic. + +If you really need a new binary sysctl number please first merge your sysctl +into the kernel and then as a separate patch allocate a binary sysctl number. + +(ebiederm@xmission.com, June 2007)