linux-kernel - Re: WARNING: at kernel/workqueue.c:1473 __queue

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Date:   Mon, 2 Mar 2020 18:00:10 +0000
From:   Robin Murphy <robin.murphy@....com>
To:     Daniel Jordan <daniel.m.jordan@...cle.com>,
        Corentin Labbe <clabbe.montjoie@...il.com>
Cc:     mark.rutland@....com, jiangshanlai@...il.com,
        linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org,
        tj@...nel.org, Will Deacon <will@...nel.org>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: WARNING: at kernel/workqueue.c:1473 __queue_work+0x3b8/0x3d0

On 02/03/2020 5:25 pm, Daniel Jordan wrote:
> On Sun, Mar 01, 2020 at 06:53:51PM +0100, Corentin Labbe wrote:
>> I tried to bisect this problem, but the result is:
> ...
>> # first bad commit: [81ff5d2cba4f86cd850b9ee4a530cd221ee45aa3] Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6
>>
>> The only interesting thing I see in this MR is: "Add fuzz testing to testmgr"
>>
>> But this wont help.
> 
> Hm, that merge commit has only a couple lines of powerpc build change, so maybe
> there's something nondeterministic going on.

Something smelled familiar about this discussion, and sure enough that 
merge contains c4741b230597 ("crypto: run initcalls for generic 
implementations earlier"), which has raised its head before[1].

> Does this fix it?  I can't verify but figure it's worth trying the simplest
> explanation first, which is that the work isn't initialized by the time it's
> queued.

The relative initcall levels would appear to explain the symptom - I 
guess the question is whether this represents a bug in a particular 
test/algorithm (as with the unaligned accesses) or a fundamental problem 
in the infrastructure now being able to poke the module loader too early.

Robin.

[1] 
https://lore.kernel.org/linux-arm-kernel/20190530170737.GB70051@gmail.com/

> thanks,
> daniel
> 
> ---8<---
> 
> Subject: [PATCH] module: statically initialize init section freeing data
> 
> Signed-off-by: Daniel Jordan <daniel.m.jordan@...cle.com>
> ---
>   kernel/module.c | 13 +++----------
>   1 file changed, 3 insertions(+), 10 deletions(-)
> 
> diff --git a/kernel/module.c b/kernel/module.c
> index 33569a01d6e1..db0cda206167 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -88,8 +88,9 @@ EXPORT_SYMBOL_GPL(module_mutex);
>   static LIST_HEAD(modules);
>   
>   /* Work queue for freeing init sections in success case */
> -static struct work_struct init_free_wq;
> -static struct llist_head init_free_list;
> +static void do_free_init(struct work_struct *w);
> +static DECLARE_WORK(init_free_wq, do_free_init);
> +static LLIST_HEAD(init_free_list);
>   
>   #ifdef CONFIG_MODULES_TREE_LOOKUP
>   
> @@ -3501,14 +3502,6 @@ static void do_free_init(struct work_struct *w)
>   	}
>   }
>   
> -static int __init modules_wq_init(void)
> -{
> -	INIT_WORK(&init_free_wq, do_free_init);
> -	init_llist_head(&init_free_list);
> -	return 0;
> -}
> -module_init(modules_wq_init);
> -
>   /*
>    * This is where the real work happens.
>    *
>