I think he isn't, Mach Exceptions are just another aproach of signals, they were used on Mach_US and Lites to implement Unix-compatible signals. The unique 'problem' is that Mach Exceptions handle not only process but also threads, so, this is a very fundamental difference.
I also dunno why Mach Exception were not used to implement Unix Signals on GNU Hurd/gLibC Written by Roland McGrath on Sat, 7 Jul 2001 14:57:09 -0400 (EDT)
I think you are confused about what Mach exceptions are. Written by Igor Khavkine on Sat, 7 Jul 2001 14:42:48 -0400 > I've been looking through the glibc code that handles signals > for Hurd. At the same time I'm writing up a some docs on that > so someone else won't have to do it again. > > What I'm surprised by is that signals are passed between processes > using simple RPC messages. Mach has an exception facility > for threads and tasks, so I thought that exceptions would be > mapped to signals and vice versa. If a thread receives an exception, > it is mapped to a signal. But this seems really strange, why > have two ways of getting signals? It just duplicates the amount > of code that needs to handle them. > > Both ways require a system call, so one is not more efficient then > the other. The only reason I can see is that exceptions do not map > directly to signals, but that's a very weak argument. Maybe it's > one of those things that was done very long ago, no-one knows why, > and no-one wants to change it? > > Thanks. > > Igor
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