From: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Date: Thu, 30 Jun 2005 16:02:18 +0000 (+0400)
Subject: [PATCH] alpha smp fix
X-Git-Tag: v2.6.13-rc2~34
X-Git-Url: https://openfabrics.org/gitweb/?a=commitdiff_plain;h=eaf05be039cf5adfba5b1846452ce89646110fdb;p=~emulex%2Finfiniband.git

[PATCH] alpha smp fix

As usual, the reason of this breakage is quite silly: in do_entIF, we
are checking for PS == 0 to see whether it was a kernel BUG() or
userspace trap.

It works, unless BUG() happens in interrupt - PS is not 0 in kernel mode
due to non-zero IPL, and the things get messed up horribly then.  In
this particular case it was BUG_ON(!irqs_disabled()) triggered in
run_posix_cpu_timers(), so we ended up shooting "current" with the
bursts of one SIGTRAP and three SIGILLs on every timer tick.  ;-)
---

diff --git a/arch/alpha/kernel/traps.c b/arch/alpha/kernel/traps.c
index fd7bd17cc96..6f509a644bd 100644
--- a/arch/alpha/kernel/traps.c
+++ b/arch/alpha/kernel/traps.c
@@ -240,7 +240,7 @@ do_entIF(unsigned long type, struct pt_regs *regs)
 	siginfo_t info;
 	int signo, code;
 
-	if (regs->ps == 0) {
+	if ((regs->ps & ~IPL_MAX) == 0) {
 		if (type == 1) {
 			const unsigned int *data
 			  = (const unsigned int *) regs->pc;