UML - Don't try to handle signals on initial process stack

Index: linux-2.6.21-mm/arch/um/os-Linux/skas/process.c
===================================================================
@@ -494,7 +494,15 @@ int start_idle_thread(void *stack, jmp_b
 		    SA_ONSTACK | SA_RESTART, SIGUSR1, SIGIO, SIGALRM,
 		    SIGVTALRM, -1);
 
-	n = UML_SETJMP(&initial_jmpbuf);
+	/*
+	 * Can't use UML_SETJMP or UML_LONGJMP here because they save
+	 * and restore signals, with the possible side-effect of
+	 * trying to handle any signals which came when they were
+	 * blocked, which can't be done on this stack.
+	 * Signals must be blocked when jumping back here and restored
+	 * after returning to the jumper.
+	 */
+	n = setjmp(initial_jmpbuf);
 	switch(n){
 	case INIT_JMP_NEW_THREAD:
 		(*switch_buf)[0].JB_IP = (unsigned long) new_thread_handler;

@@ -504,7 +512,7 @@ int start_idle_thread(void *stack, jmp_b
 		break;
 	case INIT_JMP_CALLBACK:
 		(*cb_proc)(cb_arg);
-		UML_LONGJMP(cb_back, 1);
+		longjmp(*cb_back, 1);
 		break;
 	case INIT_JMP_HALT:
 		kmalloc_ok = 0;

@@ -515,7 +523,7 @@ int start_idle_thread(void *stack, jmp_b
 	default:
 		panic("Bad sigsetjmp return in start_idle_thread - %d\n", n);
 	}
-	UML_LONGJMP(switch_buf, 1);
+	longjmp(*switch_buf, 1);
 }
 
 void initial_thread_cb_skas(void (*proc)(void *), void *arg)