On Thu, Aug 17, 2023 at 2:34 AM Zqiang <qiang.zhang1211@xxxxxxxxx> wrote:
>
> Currently, for double invoke call_rcu(), will dump rcu_head objects
> memory info, if the objects is not allocated from the slab allocator,
> the vmalloc_dump_obj() will be invoke and the vmap_area_lock spinlock
> need to be held, since the call_rcu() can be invoked in interrupt context,
> therefore, there is a possibility of spinlock deadlock scenarios.
>
> And in Preempt-RT kernel, the rcutorture test also trigger the following
> lockdep warning:
>
> BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48
> in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 1, name: swapper/0
[...]
>
> The statistics about the source of 'rhp', the kmem_valid_obj() accounts
> for more than 97.5%, and vmalloc accounts for less than 1%, this statistic
> comes from leizhen. this commit therefore drop vmalloc_dump_obj() from
> mem_dump_obj() and only check whether is vmalloc address.
> Signed-off-by: Zqiang <qiang.zhang1211@xxxxxxxxx>
> ---
> include/linux/vmalloc.h | 5 -----
> mm/util.c | 7 +++----
> mm/vmalloc.c | 14 --------------
> 3 files changed, 3 insertions(+), 23 deletions(-)
>
> diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
> index c720be70c8dd..d7c4e112a4ad 100644
> --- a/include/linux/vmalloc.h
> +++ b/include/linux/vmalloc.h
> @@ -289,10 +289,5 @@ pcpu_free_vm_areas(struct vm_struct **vms, int nr_vms)
> int register_vmap_purge_notifier(struct notifier_block *nb);
> int unregister_vmap_purge_notifier(struct notifier_block *nb);
>
> -#if defined(CONFIG_MMU) && defined(CONFIG_PRINTK)
> -bool vmalloc_dump_obj(void *object);
> -#else
> -static inline bool vmalloc_dump_obj(void *object) { return false; }
> -#endif
>
> #endif /* _LINUX_VMALLOC_H */
> diff --git a/mm/util.c b/mm/util.c
> index ddfbb22dc187..fbc007adc108 100644
> --- a/mm/util.c
> +++ b/mm/util.c
> @@ -1066,10 +1066,9 @@ void mem_dump_obj(void *object)
> if (kmem_dump_obj(object))
> return;
>
> - if (vmalloc_dump_obj(object))
> - return;
> -
> - if (virt_addr_valid(object))
> + if (is_vmalloc_addr(object))
> + type = "vmalloc memory";
> + else if (virt_addr_valid(object))
> type = "non-slab/vmalloc memory";
> else if (object == NULL)
> type = "NULL pointer";
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 93cf99aba335..224af955bcb5 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -4271,20 +4271,6 @@ void pcpu_free_vm_areas(struct vm_struct **vms, int nr_vms)
> }
> #endif /* CONFIG_SMP */
>
> -#ifdef CONFIG_PRINTK
> -bool vmalloc_dump_obj(void *object)
> -{
> - struct vm_struct *vm;
> - void *objp = (void *)PAGE_ALIGN((unsigned long)object);
> -
> - vm = find_vm_area(objp);
What about adding something like the following to vmalloc.c. Would it work?
+static struct vmap_area *find_vmap_area_trylock(unsigned long addr)
+{
+ struct vmap_area *va;
+
+ if (!spin_trylock(&vmap_area_lock))
+ return NULL;
+ va = __find_vmap_area(addr);
+ spin_unlock(&vmap_area_lock);
+
+ return va;
+}
and call it from vmalloc_dump_obj():
vm = find_vm_area_trylock(objp);
And then keep the rest of your patch as it is but add back the call to
vmalloc_dump_obj() in mem_dump_obj():
if (vmalloc_dump_obj(object))
return;
- if (virt_addr_valid(object))
+ if (is_vmalloc_addr(object))
+ type = "vmalloc memory";
+ else if (virt_addr_valid(object))
type = "non-slab/vmalloc memory";
If that still throws "sleeping function called" type warnings, then
that is a preempt RT issue because spin_trylock() on conversion to a
sleeping lock should not be sleeping as it is uncontended.
But I could be missing something and I'll look more later. But for now
off to pick up a rental car here...
thanks,
- Joel
