From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030213Ab2HGDwY (ORCPT ); Mon, 6 Aug 2012 23:52:24 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:59660 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757303Ab2HGDiO (ORCPT ); Mon, 6 Aug 2012 23:38:14 -0400 Message-Id: <20120807032757.293199808@decadent.org.uk> User-Agent: quilt/0.60-1 Date: Tue, 07 Aug 2012 04:28:03 +0100 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Mikael Pettersson , Geert Uytterhoeven , Michael Schmitz Subject: [ 08/70] m68k: Correct the Atari ALLOWINT definition In-Reply-To: <20120807032755.803571133@decadent.org.uk> X-SA-Exim-Connect-IP: 2001:470:1f08:1539:21c:bfff:fe03:f805 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Mikael Pettersson commit c663600584a596b5e66258cc10716fb781a5c2c9 upstream. Booting a 3.2, 3.3, or 3.4-rc4 kernel on an Atari using the `nfeth' ethernet device triggers a WARN_ONCE() in generic irq handling code on the first irq for that device: WARNING: at kernel/irq/handle.c:146 handle_irq_event_percpu+0x134/0x142() irq 3 handler nfeth_interrupt+0x0/0x194 enabled interrupts Modules linked in: Call Trace: [<000299b2>] warn_slowpath_common+0x48/0x6a [<000299c0>] warn_slowpath_common+0x56/0x6a [<00029a4c>] warn_slowpath_fmt+0x2a/0x32 [<0005b34c>] handle_irq_event_percpu+0x134/0x142 [<0005b34c>] handle_irq_event_percpu+0x134/0x142 [<0000a584>] nfeth_interrupt+0x0/0x194 [<001ba0a8>] schedule_preempt_disabled+0x0/0xc [<0005b37a>] handle_irq_event+0x20/0x2c [<0005add4>] generic_handle_irq+0x2c/0x3a [<00002ab6>] do_IRQ+0x20/0x32 [<0000289e>] auto_irqhandler_fixup+0x4/0x6 [<00003144>] cpu_idle+0x22/0x2e [<001b8a78>] printk+0x0/0x18 [<0024d112>] start_kernel+0x37a/0x386 [<0003021d>] __do_proc_dointvec+0xb1/0x366 [<0003021d>] __do_proc_dointvec+0xb1/0x366 [<0024c31e>] _sinittext+0x31e/0x9c0 After invoking the irq's handler the kernel sees !irqs_disabled() and concludes that the handler erroneously enabled interrupts. However, debugging shows that !irqs_disabled() is true even before the handler is invoked, which indicates a problem in the platform code rather than the specific driver. The warning does not occur in 3.1 or older kernels. It turns out that the ALLOWINT definition for Atari is incorrect. The Atari definition of ALLOWINT is ~0x400, the stated purpose of that is to avoid taking HSYNC interrupts. irqs_disabled() returns true if the 3-bit ipl & 4 is non-zero. The nfeth interrupt runs at ipl 3 (it's autovector 3), but 3 & 4 is zero so irqs_disabled() is false, and the warning above is generated. When interrupts are explicitly disabled, ipl is set to 7. When they are enabled, ipl is masked with ALLOWINT. On Atari this will result in ipl = 3, which blocks interrupts at ipl 3 and below. So how come nfeth interrupts at ipl 3 are received at all? That's because ipl is reset to 2 by Atari-specific code in default_idle(), again with the stated purpose of blocking HSYNC interrupts. This discrepancy means that ipl 3 can remain blocked for longer than intended. Both default_idle() and falcon_hblhandler() identify HSYNC with ipl 2, and the "Atari ST/.../F030 Hardware Register Listing" agrees, but ALLOWINT is defined as if HSYNC was ipl 3. [As an experiment I modified default_idle() to reset ipl to 3, and as expected that resulted in all nfeth interrupts being blocked.] The fix is simple: define ALLOWINT as ~0x500 instead. This makes arch_local_irq_enable() consistent with default_idle(), and prevents the !irqs_disabled() problems for ipl 3 interrupts. Tested on Atari running in an Aranym VM. Signed-off-by: Mikael Pettersson Tested-by: Michael Schmitz (on Falcon/CT60) [Geert Uytterhoeven: This version applies to v3.2..v3.4.] Signed-off-by: Geert Uytterhoeven Signed-off-by: Ben Hutchings --- arch/m68k/include/asm/entry.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/m68k/include/asm/entry.h b/arch/m68k/include/asm/entry.h index c3c5a86..8798ebc 100644 --- a/arch/m68k/include/asm/entry.h +++ b/arch/m68k/include/asm/entry.h @@ -33,8 +33,8 @@ /* the following macro is used when enabling interrupts */ #if defined(MACH_ATARI_ONLY) - /* block out HSYNC on the atari */ -#define ALLOWINT (~0x400) + /* block out HSYNC = ipl 2 on the atari */ +#define ALLOWINT (~0x500) #define MAX_NOINT_IPL 3 #else /* portable version */