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SubjectRe: [Fastboot] Re: Kexec on 2.5.59 problems ?
On Mon, Feb 10, 2003 at 11:07:06AM -0700, Eric W. Biederman wrote:
> Andy Pfiffer <andyp@osdl.org> writes:
>
> > On Mon, 2003-02-10 at 03:14, Suparna Bhattacharya wrote:
> > > Surprisingly though, when I tried just a simple
> > > kexec -e today (having loaded the kernel earlier on),
> > > I ran into the following Oops, consistently:
> > >
> > > I'm using kexec-tools-1.8, and this has worked for me
> > > earlier. The test system is a 4way SMP machine.
> > >
> > > Has anyone seen this as well ? (I'd already issued init 1
> > > and unmounted filesystems by this point)
>
> Hmm. Would love to know which cpu this is on...
>
> I think the primary candidate if this only occurs in smp is
> the switch_mm. It may be that modifying the init_mm is not safe,
> or it gets zapped somewhere else.
>

The following patch from Anton Blanchard's WIP kexec tree
for ppc64 seems to fix this for me. It just does a use_mm()
(routine from fs/aio.c) instead of switch_mm().

Andy could you try this out and see if it helps ?

The other change in Anton's tree that we should probably
include uses a separate kexec_mm rather than init_mm
for the mapping.

Regards
Suparna

--
Suparna Bhattacharya (suparna@in.ibm.com)
Linux Technology Center
IBM Software Labs, India

diff -u -X ../dontdiff linux-2.5.59/fs/aio.c linux-2.5.59-kexecdump/fs/aio.c
--- linux-2.5.59/fs/aio.c Fri Jan 17 07:52:06 2003
+++ linux-2.5.59-kexecdump/fs/aio.c Tue Feb 11 09:14:25 2003
@@ -539,7 +539,7 @@
return ioctx;
}

-static void use_mm(struct mm_struct *mm)
+void use_mm(struct mm_struct *mm)
{
struct mm_struct *active_mm = current->active_mm;
atomic_inc(&mm->mm_count);
--- linux-2.5.59/arch/i386/kernel/machine_kexec.c Thu Feb 6 16:31:14 2003
+++ linux-2.5.59-kexecdump/arch/i386/kernel/machine_kexec.c Tue Feb 11 09:14:05 2003
@@ -80,7 +80,8 @@
relocate_new_kernel_t rnk;

/* switch to an mm where the reboot_code_buffer is identity mapped */
- switch_mm(current->active_mm, &init_mm, current, smp_processor_id());
+ extern void use_mm(struct mm_struct *mm);
+ use_mm(&init_mm);

stop_apics();
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