From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754726Ab3CHTt4 (ORCPT ); Fri, 8 Mar 2013 14:49:56 -0500 Received: from e8.ny.us.ibm.com ([32.97.182.138]:55830 "EHLO e8.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753281Ab3CHTtz (ORCPT ); Fri, 8 Mar 2013 14:49:55 -0500 Date: Fri, 8 Mar 2013 11:49:41 -0800 From: "Paul E. McKenney" To: Steven Rostedt Cc: LKML , Andrew Morton , Ard van Breemen Subject: Re: [PATCH] init: Scream bloody murder if interrupts are enabled too early Message-ID: <20130308194941.GM3268@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <1362694743.31874.66.camel@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1362694743.31874.66.camel@gandalf.local.home> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13030819-9360-0000-0000-0000113E5B69 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 07, 2013 at 05:19:03PM -0500, Steven Rostedt wrote: > [ Andrew, can you pull this patch into -mm? ] > > As I was testing a lot of my code recently, and having several > "successes", I accidentally noticed in the dmesg this little line: > > [ 0.000000] start_kernel(): bug: interrupts were enabled *very* early, fixing it > > > Sure enough, one of my patches two commits ago enabled interrupts early. > The sad part here is that I never noticed it, and I ran several tests > with ktest too, and ktest did not notice this line. > > What ktest looks for (and so does many other automated testing scripts) > is a back trace produced by a WARN_ON() or BUG(). As a back trace was > never produced, my buggy patch could have slipped into linux-next, or > even worse, mainline. > > Adding a WARN_ON() makes this bug a little more obvious: > > [ 0.000000] PID hash table entries: 4096 (order: 3, 32768 bytes) > [ 0.000000] __ex_table already sorted, skipping sort > [ 0.000000] Checking aperture... > [ 0.000000] No AGP bridge found > [ 0.000000] Calgary: detecting Calgary via BIOS EBDA area > [ 0.000000] Calgary: Unable to locate Rio Grande table in EBDA - bailing! > [ 0.000000] Memory: 2003192k/2054848k available (4792k kernel code, 460k absent, 51196k reserved, 6277k data, 1152k init) > [ 0.000000] ------------[ cut here ]------------ > [ 0.000000] WARNING: at /home/rostedt/work/git/linux-trace.git/init/main.c:543 start_kernel+0x215/0x40e() > [ 0.000000] Hardware name: To Be Filled By O.E.M. > [ 0.000000] Modules linked in: > [ 0.000000] Pid: 0, comm: swapper/0 Not tainted 3.8.0-test+ #275 > [ 0.000000] Call Trace: > [ 0.000000] [] warn_slowpath_common+0x83/0x9b > [ 0.000000] [] warn_slowpath_null+0x1a/0x1c > [ 0.000000] [] start_kernel+0x215/0x40e > [ 0.000000] [] ? repair_env_string+0x56/0x56 > [ 0.000000] [] x86_64_start_reservations+0x10e/0x112 > [ 0.000000] [] ? early_idt_handlers+0x120/0x120 > [ 0.000000] [] x86_64_start_kernel+0x102/0x111 > [ 0.000000] ---[ end trace 1ca9c978643fe899 ]--- > [ 0.000000] start_kernel(): bug: interrupts were enabled *very* early, fixing it > [ 0.000000] Preemptible hierarchical RCU implementation. > [ 0.000000] RCU restricting CPUs from NR_CPUS=8 to nr_cpu_ids=4. > [ 0.000000] NR_IRQS:4352 nr_irqs:712 16 > [ 0.000000] Console: colour VGA+ 80x25 > [ 0.000000] console [ttyS0] enabled, bootconsole disabled > [ 0.000000] console [ttyS0] enabled, bootconsole disabled > > Do you see it? Yes, but only after looking through it three times. > Signed-off-by: Steven Rostedt Reviewed-by: Paul E. McKenney > diff --git a/init/main.c b/init/main.c > index 63534a1..f0fe0a5 100644 > --- a/init/main.c > +++ b/init/main.c > @@ -539,7 +539,7 @@ asmlinkage void __init start_kernel(void) > * fragile until we cpu_idle() for the first time. > */ > preempt_disable(); > - if (!irqs_disabled()) { > + if (WARN_ON(!irqs_disabled())) { > printk(KERN_WARNING "start_kernel(): bug: interrupts were " > "enabled *very* early, fixing it\n"); > local_irq_disable(); > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ >