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Commit 97d8f83c authored by Andrew Morton's avatar Andrew Morton Committed by Linus Torvalds
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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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 36cf3b5c

Documentation/sysctl/ctl_unnumbered.txt

0 → 100644
+22 −0
Original line number Diff line number Diff line 


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)