Messages in this thread | | | Date | Sat, 04 Sep 2010 09:47:47 +0300 | From | Pekka Enberg <> | Subject | Re: [PATCH 05/12] x86-64: Disable preemption when using TS_USEDFPU |
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On 4.9.2010 4.17, Brian Gerst wrote: > Consolidates code and fixes the below race for 64-bit. > > commit 9fa2f37bfeb798728241cc4a19578ce6e4258f25 > Author: torvalds<torvalds> > Date: Tue Sep 2 07:37:25 2003 +0000 > > Be a lot more careful about TS_USEDFPU and preemption > > We had some races where we testecd (or set) TS_USEDFPU together > with sequences that depended on the setting (like clearing or > setting the TS flag in %cr0) and we could be preempted in between, > which screws up the FPU state, since preemption will itself change > USEDFPU and the TS flag. > > This makes it a lot more explicit: the "internal" low-level FPU > functions ("__xxxx_fpu()") all require preemption to be disabled, > and the exported "real" functions will make sure that is the case. > > One case - in __switch_to() - was switched to the non-preempt-safe > internal version, since the scheduler itself has already disabled > preemption. > > BKrev: 3f5448b5WRiQuyzAlbajs3qoQjSobw > > Signed-off-by: Brian Gerst<brgerst@gmail.com> Acked-by: Pekka Enberg <penberg@kernel.org>
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