Messages in this thread | | | Date | Tue, 20 Jan 2015 09:15:42 -0500 | From | Rik van Riel <> | Subject | Re: [PATCH 1/3] x86, fpu: __kernel_fpu_begin() should clear fpu_owner_task even if use_eager_fpu() |
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On 01/19/2015 01:51 PM, Oleg Nesterov wrote: > __kernel_fpu_begin() does nothing if !__thread_has_fpu() && use_eager_fpu(), > perhaps it assumes that this case is simply impossible. This is certainly > not possible if in_interrupt() == T; interrupted_user_mode() should have > FPU, and interrupted_kernel_fpu_idle() should fail if !__thread_has_fpu(). > > However, even if use_eager_fpu() == T a task can do drop_fpu(), then switch > to another thread which becomes fpu_owner_task, then resume and call some > function which does kernel_fpu_begin(). Say, an exiting task does a lot of > things after exit_thread(), it is not safe to assume that it can't use FPU > in these paths. > > Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
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