Re: [PATCH] vm_page.c: fix a deadlock when running with smp enabled

[Samuel Thibault]

Applied, thanks!

Etienne Brateau, le lun. 02 déc. 2024 19:27:17 +0100, a ecrit:
> the call vm_page_seg_pull_cache_page() return an vm_page (src) with his
> object being locked, as we don’t unlock before doing the vm_page_insert,
> it is still lock there, and so trying to relock it cause a deadlock.
> Replace this lock by an assert.
> This case was not seen as for non-smp locking is a no-op.
> ---
>  vm/vm_page.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/vm/vm_page.c b/vm/vm_page.c
> index 286fe62f..e329354f 100644
> --- a/vm/vm_page.c
> +++ b/vm/vm_page.c
> @@ -1036,7 +1036,8 @@ vm_page_seg_balance_page(struct vm_page_seg *seg,
>      simple_unlock(&seg->lock);
>      simple_unlock(&vm_page_queue_free_lock);
>  
> -    vm_object_lock(object);
> +    // object is already locked as vm_page_seg_alloc_from_buddy return it 
> locked
> +    assert(vm_object_lock_taken(src->object) != 0);
>      vm_page_insert(dest, object, offset);
>      vm_object_unlock(object);
>  
> -- 
> 2.47.0
> 
>