Messages in this thread | | | Date | Thu, 29 Jan 2015 16:54:09 -0500 | From | Rik van Riel <> | Subject | Re: [PATCH 2/3] x86, fpu: unlazy_fpu: don't do __thread_fpu_end() if use_eager_fpu() |
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On 01/29/2015 04:08 PM, Oleg Nesterov wrote: > unlazy_fpu()->__thread_fpu_end() doesn't look right if use_eager_fpu(). > Unconditional __thread_fpu_end() is only correct if we know that this > thread can't return to user-mode and use FPU. > > Fortunately it has only 2 callers. fpu_copy() checks use_eager_fpu(), > and init_fpu(current) can be only called by the coredumping thread via > regset->get(). But it is exported to modules, and imo this should be > fixed anyway. > > And if we check use_eager_fpu() we can use __save_fpu() like fpu_copy() > and save_init_fpu() do. > > - It seems that even !use_eager_fpu() case doesn't need the unconditional > __thread_fpu_end(), we only need it if __save_init_fpu() returns 0. > > - It is still not clear to me if __save_init_fpu() can safely nest with > another save + restore from __kernel_fpu_begin(). If not, we can use > kernel_fpu_disable() to fix the race. > > Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
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