Looks like a braino that used to be fixed in e.g. #next.alpha
had gotten into alpha.git cherry-picked version of that patch.
Sure, alpha has no preempt, but preempt_enable() in place of
preempt_disable() is actively confusing the readers...
Other than that, the cherry-picked variant matches what I have.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
 
        if (unlikely(reg >= 32))
                return 0;
-       preempt_enable();
+       preempt_disable();
        if (current_thread_info()->status & TS_SAVED_FP)
                val = current_thread_info()->fp[reg];
        else switch (reg) {
        if (unlikely(reg >= 32))
                return 0;
 
-       preempt_enable();
+       preempt_disable();
        if (current_thread_info()->status & TS_SAVED_FP) {
                LDT(0, current_thread_info()->fp[reg]);
                STS(0, val);