Bug 14001

Summary:	eventfd manpage missing EFD_SEMAPHORE flag
Product:	Documentation	Reporter:	Anton Blanchard (anton)
Component:	man-pages	Assignee:	documentation_man-pages (documentation_man-pages)
Status:	RESOLVED CODE_FIX
Severity:	normal	CC:	mtk.manpages
Priority:	P1
Hardware:	All
OS:	Linux
Kernel Version:		Subsystem:
Regression:	No	Bisected commit-id:

Description Anton Blanchard 2009-08-18 05:38:38 UTC

I noticed eventfd added a new flag, EFD_SEMAPHORE which isn't documented
in the git manpages tree:

http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=bcd0b235bf3808dec5115c381cd55568f63b85f0

Comment 1 Michael Kerrisk 2010-08-30 05:29:50 UTC

For man-pages-3.26, I added this text:

       EFD_SEMAPHORE (since Linux 2.6.30)
              Provide semaphore-like semantics  for  reads  from
              the new file descriptor.  See below.
...
              *  If EFD_SEMAPHORE  was  not  specified  and  the
                 eventfd  counter  has  a  nonzero value, then a
                 read(2) returns 8 bytes containing that  value,
                 and the counter's value is reset to zero.

              *  If  EFD_SEMAPHORE was specified and the eventfd
                 counter has a nonzero  value,  then  a  read(2)
                 returns 8 bytes containing the value 1, and the
                 counter's value is decremented by 1.