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On Tue, Jun 07, 2005 at 10:45:58AM -0700, Matt Thomas wrote:
> David Laight wrote:
> >On Tue, Jun 07, 2005 at 10:38:20AM -0700, Matt Thomas wrote:
> >
> >>>Yes. The MD syscall code checks for the SYSCALL_MPSAFE flag and
> >>>doesn't take the big-lock if it's set. It's currently only set for
> >>>getpid(). Exactly what else it could be easily applied to is less
> >>>clear; getpid() is the only true no-brainer that requires taking no
> >>>locks on anything at all.
> >>
> >>get*gid?
> >>get*uid?
> >
> >
> >While another thread is doing set*[gu]id ?
>=20
> Unless your process is taking care to do mutexes to control
> ordering, the result you get back will be unpredictable (did
> the set* run before or after the get*).  So you can treat
> them as unlocked since the user code has to have some method
> of serialization to get a meaningful answer.

What you said. Assuming, of course, that the read operation itself
is atomic.

	-is
--=20
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