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authorAndrew Morton <akpm@linux-foundation.org>2007-07-16 02:41:20 -0400
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-07-16 12:05:49 -0400
commit97d8f83cb734525f96992fd61e4f7323ab3d549c (patch)
tree23f1859ea95f3438deb845b6082bad2fc9d1d41e /Documentation
parent36cf3b5c3b7228bcf5124c530d50080b61a59f69 (diff)
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" <ebiederm@xmission.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/sysctl/ctl_unnumbered.txt22
1 files changed, 22 insertions, 0 deletions
diff --git a/Documentation/sysctl/ctl_unnumbered.txt b/Documentation/sysctl/ctl_unnumbered.txt
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index 000000000000..23003a8ea3e7
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+++ b/Documentation/sysctl/ctl_unnumbered.txt
@@ -0,0 +1,22 @@
1
2Except for a few extremely rare exceptions user space applications do not use
3the binary sysctl interface. Instead everyone uses /proc/sys/... with
4readable ascii names.
5
6Recently the kernel has started supporting setting the binary sysctl value to
7CTL_UNNUMBERED so we no longer need to assign a binary sysctl path to allow
8sysctls to show up in /proc/sys.
9
10Assigning binary sysctl numbers is an endless source of conflicts in sysctl.h,
11breaking of the user space ABI (because of those conflicts), and maintenance
12problems. A complete pass through all of the sysctl users revealed multiple
13instances where the sysctl binary interface was broken and had gone undetected
14for years.
15
16So please do not add new binary sysctl numbers. They are unneeded and
17problematic.
18
19If you really need a new binary sysctl number please first merge your sysctl
20into the kernel and then as a separate patch allocate a binary sysctl number.
21
22(ebiederm@xmission.com, June 2007)