Fixing Posix semaphores
joe at zircon.seattle.wa.us
Mon Dec 13 14:39:16 PST 2004
On Mon, 2004-12-13 at 14:21 -0800, Julian Elischer wrote:
> Joe Kelsey wrote:
> >I have a desire to fix posix semaphores in at least 5.3. The current
> >implementation doesn't actually follow the "spirit" of the standard,
> >even though it technically qualifies in a somewhat degraded sense. I
> >refer to the fact that the current implementation treats posix
> >semaphores as completely contained inside the kernel and essentially
> >divorced from the filesystem. The true "spirit" of the standard places
> >the semaphores directly in the file system, similar to named pipes.
> >However the current implementation treats the supplied "name" as a
> >14-character identifier, required to begin with a slash and contain no
> >other slashes. Pretty weak.
> >Well, in order to fix this, we need to add file system code and come up
> >with a new type. I currently have some time to spend on something like
> >this and am willing to put in whatever effort it takes. Does anyone
> >want to add their own ideas or requirements?
> >I currently run 5.3, but I suppose I could think about running current
> >at some point in the future.
> I don't think that the spirit is to do what you suggest.
> I have always interpretted it to be a separate namespace.
> does the posix "mknod" definition mention how to make a semaphore?
POSIX does not define or allow use of mknod to create a named semaphore.
Only sem_open() can create a named semaphore. The "spirit", as
implemented in other OS', clearly indicates the use of file system
names, not the restricted 14-character name used by FreeBSD. For
instance, Solaris uses file system names.
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