On Tue, Jun 07, 2005 at 01:30:53PM -0400, Nathan J. Williams wrote:
> Thor Lancelot Simon <tls@rek.tjls.com> writes:
> 
> > To a cursory examination, it looks like it's possible that a number of
> > syscalls that touch only process state (particularly read-only ones
> > like getcwd, getpid, etc. but also some that change state, like
> > chdir, chroot, and a few others) could easily take subsystem locks
> > instead of the giant lock.
> > 
> > Is this correct?
> 
> 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.

The vnode locks needed for getcwd() certainly _ought_ to be MP-safe,
no?  What's the point of having them there if they aren't?

The other one that comes immediately to mind, though, is gettimeofday().
Oh, and getppid() and getrlimit(), maybe.

-- 
 Thor Lancelot Simon	                                      tls@rek.tjls.com

"The inconsistency is startling, though admittedly, if consistency is to be
 abandoned or transcended, there is no problem."		- Noam Chomsky