linux-kernel - Re: [PATCH] rhashtable: Fix potential deadlock by moving schedule

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Message-ID: <afb5abb3-8060-42ed-bb8f-48fb13d99d0c@linux.ibm.com>
Date: Fri, 10 Jan 2025 15:46:55 +0100
From: Zaslonko Mikhail <zaslonko@...ux.ibm.com>
To: Herbert Xu <herbert@...dor.apana.org.au>, Breno Leitao <leitao@...ian.org>
Cc: Michael Kelley <mhklinux@...look.com>,
        "saeedm@...dia.com" <saeedm@...dia.com>,
        "tariqt@...dia.com" <tariqt@...dia.com>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>, Thomas Graf <tgraf@...g.ch>,
        Tejun Heo <tj@...nel.org>, Hao Luo <haoluo@...gle.com>,
        Josh Don <joshdon@...gle.com>, Barret Rhoden <brho@...gle.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>
Subject: Re: [PATCH] rhashtable: Fix potential deadlock by moving
 schedule_work outside lock

Herbert and Breno,

On 10.01.2025 10:27, Herbert Xu wrote:
> On Thu, Jan 09, 2025 at 02:15:17AM -0800, Breno Leitao wrote:
> 
> Reported-by: Michael Kelley <mhklinux@...look.com>
> Fixes: e1d3422c95f0 ("rhashtable: Fix potential deadlock by moving schedule_work outside lock")
> Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>
> 
> diff --git a/lib/rhashtable.c b/lib/rhashtable.c
> index bf956b85455a..e196b6f0e35a 100644
> --- a/lib/rhashtable.c
> +++ b/lib/rhashtable.c
> @@ -621,7 +621,7 @@ static void *rhashtable_try_insert(struct rhashtable *ht, const void *key,
>  
>  			rht_unlock(tbl, bkt, flags);
>  
> -			if (PTR_ERR(data) == -ENOENT && !new_tbl) {
> +			if (!new_tbl) {
>  				atomic_inc(&ht->nelems);
>  				if (rht_grow_above_75(ht, tbl))
>  					schedule_work(&ht->run_work);

I'd like to let you know that I was getting OOM failure on s390 when booting
the kernel (linux-next20250109) with limited memory (mem=1G kernel parameter).
Problem took place in both zVM and LPAR environments. Bisecting also revealed
the commit e1d3422c95f0 ("rhashtable: Fix potential deadlock by moving
schedule_work outside lock").
Afterwards, I tried the fix from Herbert above and the error does not appear
any more. So it seems to resolve the issue.

Thanks,
Mikhail