On Thu, Aug 16, 2001 at 02:34:45PM -0700, Jun Sun wrote:
> Yes, that is somewhat the purpose. Essentially we want to see, at the
> beginning of a signal handler execution, the process appears to have not used
> FPU at all.
Why?
> This requirement might be a must, because whether clearing current->used_math
> bit determine which patch we will take in the do_cpu(), when signal handler
> uses FPU for the first time. See the code below.
>
> if (current->used_math) { /* Using the FPU again. */
> lazy_fpu_switch(last_task_used_math);
> } else { /* First time FPU user. */
> init_fpu();
> current->used_math = 1;
> }
> last_task_used_math = current;
>
> Clearly the second path is logically the correct one.
Not really. Why should it get a clean set of FP registers? I think
the CORRECT thing would actually be for it to have the app's FP
registers. Changes should not propogate back to the app, that's all.
> BTW, do I see another bug here in do_cpu()? It seems that before we call
> init_fpu(), we should check last_task_used_math. If it is not NULL, we should
> save the FP state to the last_task_used_math. Hmm, strange ...
I thought I got all of these... <sigh>
--
Daniel Jacobowitz Carnegie Mellon University
MontaVista Software Debian GNU/Linux Developer
