Gilles Chanteperdrix wrote:
> Tomas Kalibera wrote:
> > Gilles Chanteperdrix wrote:
> > > Tomas Kalibera wrote:
> > > >
> > > > Hi Gilles,
> > > >
> > > > I've recompiled the kernel again from scratch and got the same lock
> up.
> > > > Fix 5 does not help... If you want to inspect the exact kernel I
> used,
> > > > it's again at http://www.cs.purdue.edu/~tkaliber/crash, the one with
> > > > "p5" in its name.
> > > >
> > > > Tomas
> > >
> > > But... do you get the lock-up without the patch ?
> > >
> > >
> > No. Or, more precisely, not the same one. With this patch (5), the
> > system locks up as soon as the application starts. It does not print
> > any stack trace.
> > Without the patch, the system gets to unusable state when the
> > application calls clone/fork, and it does produce a stack trace (those I
> > was sending you before). It seems to be more alive (processes start, but
> > crash, because of garbled preempt_count).
> >
> > The crashes are perfectly repeatable on the system I have. So, the
> > crashes make no sense to you, right ? I can indeed try to go the
> > defensive path and try an older kernel or something, but if there is a
> > Xenomai bug, it would be nice to find it... The same for kernel bug,
> > indeed.
>
> Of course, we are looking for all bugs. But please tell me: do you get
> the lock-up even before fork is called ? If not, could you verify that
> at least some Xenomai programs run correctly, for instance latency ?
> Looking at the code, I think I found a bug, but I doubt it could cause a
> lockup. The definition of VM_PINNED in include/linux/mm.h collides with
> another bit used by Linux, so this defintion should be changed from:
> #define VM_PINNED 0x08000000
> to:
> #define VM_PINNED 0x10000000
Here comes a 6th patch for this bug, (patch 6 includes patch 5).
--
Gilles.
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 7f27db6..a0c80c7 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -104,10 +104,11 @@ extern unsigned int kobjsize(const void *objp);
#define VM_MAPPED_COPY 0x01000000 /* T if mapped copy of data (nommu
mmap) */
#define VM_INSERTPAGE 0x02000000 /* The vma has had "vm_insert_page()"
done on it */
#define VM_ALWAYSDUMP 0x04000000 /* Always include in core dumps */
-#define VM_PINNED 0x08000000 /* Disable faults for the vma */
#define VM_CAN_NONLINEAR 0x08000000 /* Has ->fault & does nonlinear pages */
+#define VM_PINNED 0x10000000 /* Disable faults for the vma */
+
#ifndef VM_STACK_DEFAULT_FLAGS /* arch can override this */
#define VM_STACK_DEFAULT_FLAGS VM_DATA_DEFAULT_FLAGS
#endif
diff --git a/mm/memory.c b/mm/memory.c
index e0e7a3d..32d6cb6 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -584,8 +584,14 @@ again:
if (is_cow_mapping(vma->vm_flags)) {
if (((vma->vm_flags|src_mm->def_flags) &
(VM_LOCKED|VM_PINNED))
== (VM_LOCKED|VM_PINNED)) {
+ arch_leave_lazy_mmu_mode();
+ spin_unlock(src_ptl);
+ pte_unmap_nested(src_pte);
+ add_mm_rss(dst_mm, rss[0], rss[1]);
+ pte_unmap_unlock(dst_pte, dst_ptl);
+ cond_resched();
do_cow_break = 1;
- break;
+ goto again;
}
}
}
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