[uml-devel] Re: [patch 7/7] uml: retry host close() on EINTR

[Paolo Ornati <ornati@fastwebnet.it>]

On Sat, 10 Sep 2005 12:00:01 -0700 (PDT)
Linus Torvalds <torvalds@osdl.org> wrote:

> Re-doing the close() is the wrong thing to do, since in a threaded 
> environment, something else might have opened another file, gotten
> the same file descriptor, and you now close _another_ file.

So glibc doc is wrong here:

http://www.gnu.org/software/libc/manual/html_node/Opening-and-Closing-Files.html#index-close-1197

-----------------------------------------------------------------------
The normal return value from close is 0; a value of -1 is returned in
case of failure. The following errno error conditions are defined for
this function:

...

EINTR
    The close call was interrupted by a signal. See Interrupted
Primitives. Here is an example of how to handle EINTR properly:

               TEMP_FAILURE_RETRY (close (desc));
-----------------------------------------------------------------------


And: /usr/include/unistd.h

# define TEMP_FAILURE_RETRY(expression)		\
  (__extension__				\
    ({ long int __result;			\
       do __result = (long int) (expression);	\
       while (__result == -1L && errno == EINTR); \
       __result; }))
#endif


SUSV3:
-------------------------------------------------------------
If close() is interrupted by a signal that is to be caught, it shall
return -1 with errno set to [EINTR] and the state of fildes is
unspecified
-------------------------------------------------------------

Unspecified! ;-)

-- 
	Paolo Ornati
	Linux 2.6.13.1 on x86_64


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