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] [<ffffffff8103781d>] warn_slowpath_common+0x83/0x9b > [ 0.000000] [<ffffffff8103784f>] warn_slowpath_null+0x1a/0x1c > [ 0.000000] [<ffffffff81ae5a30>] start_kernel+0x215/0x40e > [ 0.000000] [<ffffffff81ae5623>] ? repair_env_string+0x56/0x56 > [ 0.000000] [<ffffffff81ae5312>] x86_64_start_reservations+0x10e/0x112 > [ 0.000000] [<ffffffff81ae5120>] ? early_idt_handlers+0x120/0x120 > [ 0.000000] [<ffffffff81ae5418>] 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 <[email protected]> Reviewed-by: Paul E. McKenney <[email protected]> > 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 [email protected] > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
