Messages in this thread | | | Subject | Re: PATCH? process_32.c:__switch_to() calls __math_state_restore() before updating current_task | From | Suresh Siddha <> | Date | Mon, 08 Feb 2010 10:48:10 -0800 |
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On Fri, 2010-02-05 at 04:44 -0800, Oleg Nesterov wrote: > Could you please explain me another issue? I know nothing about fpu > handling, I am reading this code trying to understand the unrelated > bug with the old kernel. > > In short: why restore_i387_xstate() does init_fpu() when !used_math(), > can't (or shouldn't) it merely do set_used_math() ? > > restore_i387_xstate: > > if (!used_math()) { > err = init_fpu(tsk); > if (err) > return err; > } > > note that buf != NULL. This means that used_math() was true when > get_sigframe() was called, otherwise buf == sigcontext->fpstate > would be NULL, right?
No. When the signal is delivered sigcontext->fpstate can be null and when we return from the signal handler, user can update the sigcontext->fpstate pointer and the user expects the kernel to update the fpstate of the process accordingly.
> So, the task must have the valid ->thread.xstate,
Need not be.
thanks, suresh
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