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authorAndrew Morton <akpm@linux-foundation.org>2007-07-15 23:41:20 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-07-16 09:05:49 -0700
commit97d8f83cb734525f96992fd61e4f7323ab3d549c (patch)
tree23f1859ea95f3438deb845b6082bad2fc9d1d41e /Documentation/sysctl
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/sysctl')
-rw-r--r--Documentation/sysctl/ctl_unnumbered.txt22
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diff --git a/Documentation/sysctl/ctl_unnumbered.txt b/Documentation/sysctl/ctl_unnumbered.txt
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+
+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)