Re: 2.6.25-mm1

[Andres Salomon <dilinger@queued.net>]

On Fri, 18 Apr 2008 20:29:25 -0700
Andrew Morton <akpm@linux-foundation.org> wrote:

> On Fri, 18 Apr 2008 23:10:24 -0400 Joseph Fannin <jfannin@gmail.com> wrote:
> 
> > On Fri, Apr 18, 2008 at 01:47:57AM -0700, Andrew Morton wrote:
> > >
> > > ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.25/2.6.25-mm1/
> > 
> > New, in 2.6.25-mm1 is a hang I'm seeing, just after the kernel prints:
> > 
> > "[    0.160375] NET: Registered protocol family 16"
> > 
> > The hang lasts about five minutes, and then boot continues.
> 
> Please add initcall_debug to the kernel boot command line - that should
> narrow it down.
> 
> >  Just
> > after that, a backtrace is printed; I don't know if it's related.  The
> > backtrace will follow.
> > 
> > This does not occur in mainline.  It seems it might be related to OLPC
> > support -- I enabled all those options -- but that's not good
> > behavior, and I see no warning of thus in the help.
> > 
> > I'm sending a number or reports against 2.6.25-mm1, so I've put my
> > dmesg and .config on a server:
> > 
> > http://home.columbus.rr.com/jfannin3/dmesg.txt
> > http://home.columbus.rr.com/jfannin3/config-2.6.25-mm1.txt
> > 
> > [    0.160375] NET: Registered protocol family 16
> > [  400.782683] ------------[ cut here ]------------
> > [  400.782832] WARNING: at arch/x86/mm/ioremap.c:158 __ioremap_caller+0x27d/0x2e0()
> > [  400.783022] Modules linked in:
> > [  400.783169] Pid: 1, comm: swapper Not tainted 2.6.25-mm1 #7
> > [  400.783300]  [<c0130fa9>] warn_on_slowpath+0x59/0x80
> > [  400.783480]  [<c0106c2e>] ? profile_pc+0x3e/0x50
> > [  400.783682]  [<c01374ee>] ? irq_exit+0x4e/0xa0
> > [  400.783879]  [<c0115aec>] ? smp_apic_timer_interrupt+0x5c/0x90
> > [  400.784087]  [<c024314c>] ? trace_hardirqs_on_thunk+0xc/0x10
> > [  400.784298]  [<c01552cd>] ? trace_hardirqs_on_caller+0xcd/0x150
> > [  400.784506]  [<c024314c>] ? trace_hardirqs_on_thunk+0xc/0x10
> > [  400.784706]  [<c010416c>] ? restore_nocheck_notrace+0x0/0xe
> > [  400.784906]  [<c011d0e6>] ? page_is_ram+0xa6/0xd0
> > [  400.785059]  [<c011d4ed>] __ioremap_caller+0x27d/0x2e0
> > [  400.785221]  [<c03569d8>] ? _spin_unlock_irqrestore+0x48/0x80
> > [  400.785421]  [<c017f4cd>] ? ftrace_record_ip+0x7d/0x250
> > [  400.785621]  [<c0474801>] ? olpc_init+0x31/0x140
> > [  400.785817]  [<c011d59f>] ioremap_nocache+0x1f/0x30
> > [  400.785976]  [<c0474801>] ? olpc_init+0x31/0x140
> > [  400.786165]  [<c0474801>] olpc_init+0x31/0x140
> > [  400.786318]  [<c0464992>] kernel_init+0x142/0x2d0
> > [  400.786479]  [<c01552cd>] ? trace_hardirqs_on_caller+0xcd/0x150
> > [  400.786680]  [<c010416c>] ? restore_nocheck_notrace+0x0/0xe
> > [  400.786879]  [<c0464850>] ? kernel_init+0x0/0x2d0
> > [  400.787069]  [<c0464850>] ? kernel_init+0x0/0x2d0
> > [  400.787260]  [<c0104d9b>] kernel_thread_helper+0x7/0x10
> > [  400.787422]  =======================
> > [  400.787727] ---[ end trace 4eaa2a86a8e2da22 ]---
> 
> <looks at this again>
> 
> That's
> 
>                 WARN_ON_ONCE(is_ram);
> 
> the changelog for the patch which added that warning is information-free
> and there's no code comment explaining what went wrong, which makes things
> rather harder than they ought to be.
> 
> Yes it's due to the new OLPC code.  olpc_init() has
> 
> 	romsig = ioremap(0xffffffc0, 16);
> 
> which we probably just shouldn't do this at all unless we're running on the
> OLPC hardware.  But we need to do this to find out if we're running on the OLPC
> hardware!  Perhaps the warning should just be removed.

Hm.  We could either protect that code with an:

if (!is_geode())
  return;

Or I could add the OpenFirmware patches which would allow us to get
rid of this code, and instead check for the existence of OFW using
that.

The former is quick and easy; the latter is (imo) nicer, so long as
people don't have problems w/ the OFW code.  :)


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