sparc64: Fix hardirq tracing in trap return path.

We can overflow the hardirq stack if we set the %pil here so early, just let the normal control flow do it. This is fine as we are allowed to do the actual IRQ enable at any point after we call trace_hardirqs_on. Signed-off-by: David S. Miller <[email protected]>
mna · Apr 20, 2010 · 28a1f53 · 28a1f53
1 parent baa0677
commit 28a1f53
Showing 1 changed file with 11 additions and 1 deletion.
diff --git a/arch/sparc/kernel/rtrap_64.S b/arch/sparc/kernel/rtrap_64.S
@@ -130,7 +130,17 @@ rtrap_xcall:
 		 nop
 		call			trace_hardirqs_on
 		 nop
-		wrpr			%l4, %pil
+		/* Do not actually set the %pil here.  We will do that
+		 * below after we clear PSTATE_IE in the %pstate register.
+		 * If we re-enable interrupts here, we can recurse down
+		 * the hardirq stack potentially endlessly, causing a
+		 * stack overflow.
+		 *
+		 * It is tempting to put this test and trace_hardirqs_on
+		 * call at the 'rt_continue' label, but that will not work
+		 * as that path hits unconditionally and we do not want to
+		 * execute this in NMI return paths, for example.
+		 */
 #endif
 rtrap_no_irq_enable:
 		andcc			%l1, TSTATE_PRIV, %l3