> The FPU stuff is still pending, I fear. I haven't heard anything from
> Suresh so I suspect I'm going to have to dig into the init specifics
> myself and fix up the patchset.
As I mentioned a couple of weeks ago in the "[PATCH] Make
math_state_restore() save and restore the interrupt flag" thread,
I've been running with just Suresh's second patch for the last month,
and it's cured all my symptoms.
Although, just as a minor style point, I might reduce the
number of levels if indentation by rewriting it as:
void __kernel_fpu_end(void)
{
- if (use_eager_fpu())
- math_state_restore();
- else
+ if (!use_eager_fpu()) {
stts();
+ } else if (likely(tsk_used_math(current)))
+ math_state_restore();
+ }
+ /*
+ * When using eager fpu, tsk_used_math() is almost always true,
+ * and we restore the user math state eagerly. In some special
+ * cases during thread exit, signal handling etc, tsk_used_math()
+ * is false. Those few places will take proper actions, so we
+ * don't need to restore the math here.
+ */
}
EXPORT_SYMBOL(__kernel_fpu_end);
Truthfully, the idea I like best is Linus's proposal to postpone all
such adjustments to the processor state until the return to user space,
so multiple kernel_fpu_begin()/_end() pairs become much cheaper:
http://marc.info/?l=linux-kernel&m=139128398717816
Hoerver, that deep into Here Be Dragons code is somewhere I fear to tread,
so I'm hoping someone braver than I is inspired.
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