[IA64] restore_sigcontext is not preempt safe

restore_sigcontext calls ia64_set_local_fpu_owner() which requires that
preempt be disabled.

Signed-off-by: Keith Owens <kaos@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

arch/ia64/kernel/signal.c

@@ -143,13 +143,15 @@ restore_sigcontext (struct sigcontext __user *sc, struct sigscratch *scr)
 
 		__copy_from_user(current->thread.fph, &sc->sc_fr[32], 96*16);
 		psr->mfh = 0;	/* drop signal handler's fph contents... */
+		preempt_disable();
 		if (psr->dfh)
 			ia64_drop_fpu(current);
 		else {
 			/* We already own the local fph, otherwise psr->dfh wouldn't be 0.  */
 			__ia64_load_fpu(current->thread.fph);
 			ia64_set_local_fpu_owner(current);
 		}
+		preempt_enable();
 	}
 	return err;
 }