Date: Fri, 11 Apr 2003 11:12:12 -0700 (PDT) From: Julian Elischer <julian@elischer.org> To: Daniel Eischen <eischen@pcnet1.pcnet.com> Cc: freebsd-threads@freebsd.org Subject: Re: patch for %gs saving Message-ID: <Pine.BSF.4.21.0304111111550.99022-100000@InterJet.elischer.org> In-Reply-To: <Pine.GSO.4.10.10304110846410.12636-100000@pcnet1.pcnet.com>
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On Fri, 11 Apr 2003, Daniel Eischen wrote: > On Fri, 11 Apr 2003, David Xu wrote: > > ----- Original Message ----- > > From: "Daniel Eischen" <eischen@pcnet1.pcnet.com> > > To: "David Xu" <davidxu@freebsd.org> > > Cc: <freebsd-threads@freebsd.org> > > Sent: Friday, April 11, 2003 1:55 PM > > Subject: Re: patch for %gs saving > > > > > > > On Fri, 11 Apr 2003, David Xu wrote: > > > > Here is the patch for kernel to save %gs, > > > > it works well on my machine. > > > > http://people.freebsd.org/~davidxu/i386_gs.diff > > > > > > Thanks, I'll give it a go. > > > > > > > Daniel, is this the reason in your libpthread > > > > patch that doesn't use getcontext syscall ? > > > > > > No, we already had userland versions of getcontext() > > > so I simply reused them to avoid the system call. > > > That's why THR_GETCONTEXT is a macro; it can be > > > defined to be getcontext() for those archs that > > > don't have userland versions and want to use the > > > system call instead. > > > > > > Note that we still need userland versions of > > > _thread_switch() and _thread_enter_uts() anyways, > > > so writing a userland [gs]etcontext() is probably > > > pretty simple once you have those. > > > > > > Plus, when you get a context in order to make a > > > context for a new thread, you still can't rely on > > > %gs because it may be scheduled on another KSE or > > > the thread could be a scope system thread in which > > > case it be scheduled in another KSEG. So the current > > > %gs isn't necessarily correct for a new thread. > > > > > > Hmm, this raises a good point. Once you set up a > > > thread to run a signal handler, the %gs register has > > > already been set. We have to be sure that the > > > interrupted context and the thread's new (signal) > > > context both have the same %gs and that it runs on > > > the correct KSE. Either that, or we have to be able > > > to change the contexts to be the correct %gs before > > > running the thread and invoking the handler. > > > > > > > I think those code shouldn't touch %gs, these includes > > _thread_switch(), _thread_enter_uts(), they don't know > > there is a %gs register. Execept kse_entry(), when first > > time an upcall is made, it sets %gs to its own LDT, I > > think you have already done this, but _thread_switch(), > > and _thread_enter_uts() might be change to not touch %gs. > > getcontext() and setcontext() still touch %gs though. > If an application uses those functions and they are > used in a thread once while it is on one KSE and > another time while it is on a different KSE, then > %gs gets hosed. they should not touch %gs > > -- > Dan Eischen > > _______________________________________________ > freebsd-threads@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-threads > To unsubscribe, send any mail to "freebsd-threads-unsubscribe@freebsd.org" >
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