David S. Miller wrote:
On Wed, 19 Jan 2005 20:48:37 +0100
Krzysztof Helt <[EMAIL PROTECTED]> wrote:
How should it be done? Should copy_flags() during do_fork() preserve
FPU context/registers for child task? Should SMP and UP context
switching be handled differently?
copy_thread(), via do_fork(), copies the FPU state in this code here:
#ifndef CONFIG_SMP
if(last_task_used_math == current) {
#else
if(current_thread_info()->flags & _TIF_USEDFPU) {
#endif
put_psr(get_psr() | PSR_EF);
fpsave(&p->thread.float_regs[0], &p->thread.fsr,
&p->thread.fpqueue[0], &p->thread.fpqdepth);
#ifdef CONFIG_SMP
current_thread_info()->flags &= ~_TIF_USEDFPU;
#endif
}
It is not enough or I do not understand something. The new thread will
have a _TIF_USEDFPU flag disabled (if not cleared here, it is cleared in
copy_flags() in the do_fork()). So, a FP disabled trap handler will
initialize FPU state from default values, not from the ones saved here.
BTW, the new thread is p or current in the copy_thread function? I
suppose it is current.
Krzysztof
-
To unsubscribe from this list: send the line "unsubscribe sparclinux" in
the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
