Here's an attempt at a fix. This change reenables soft interrupts in
the UserGenException code, just after the return from trap() (note
that trap() will have already reenabled hard interrupts). The idea is
to allow any pending soft interrupts to run before returning to user
mode.

This change isn't necessary for the ps2, since that port doesn't use
the processor's interrupts for soft interrupts, hence the #ifndef
IPL_ICU_MASK.

Does anyone have any objects to committing this change? It's been
tested by Emmanuel Dreyfus.

$NetBSD: mipsX_subr.S,v 1.10 2002/11/12 14:00:41 nisimura Exp $

- S

--- mipsX_subr.S.orig	Fri Nov 15 17:40:55 2002
+++ mipsX_subr.S	Sun Nov 17 13:57:47 2002
@@ -737,6 +737,20 @@
 	COP0_SYNC
 	jal	_C_LABEL(trap)
 	sw	a3, CALLFRAME_SIZ-4(sp)		# for debugging
+#ifndef IPL_ICU_MASK
+/*
+ * Allow any pending soft interrupts to run. This is needed in the case
+ * of an exception occurring immediately after the return from exception
+ * which would prevent the soft interrupt triggering.
+ */
+	mfc0	t2, MIPS_COP_0_STATUS
+	REG_L	t0, CALLFRAME_SIZ + FRAME_SR(sp)
+	and	t0, t0, MIPS_INT_MASK
+	DYNAMIC_STATUS_MASK_TOUSER(t0, t1)	# machine dependent masking
+	or	t0, t0, t2
+	mtc0	t0, MIPS_COP_0_STATUS
+	COP0_SYNC
+#endif
 /*
  * Check pending asynchronous traps.
  */