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Fri, 06 Nov 2026 06:43:25 -0800 (PST) Received: from milan ([2001:9b1:d5a0:a500::24b]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-c4d35631eb2sm86304166b.27.2026.11.06.06.43.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 06 Nov 2026 06:43:24 -0800 (PST) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Fri, 6 Nov 2026 15:43:21 +0100 To: Linus Torvalds Cc: Uladzislau Rezki , Herbert Xu , "Liam R. Howlett (Google)" , Davidlohr Bueso , Michal Hocko , Baoquan He , Alexander Potapenko , Andrey Ryabinin , Marco Elver , Michal Hocko , Linux Crypto Mailing List , Andrew Morton , Thomas Graf , linux-mm@kvack.org, linux-kernel@vger.kernel.org, maple-tree@lists.infradead.org, Lorenzo Stoakes , Chris Mason , Alice Ryhl , Andrew Ballance , stable@vger.kernel.org, "David Hildenbrand (Arm)" Subject: Re: [PATCH 4/4] rhashtable: fix vmalloc() deadlock in atomic rehash Message-ID: References: X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Thu, Nov 05, 2026 at 01:02:35PM -0800, Linus Torvalds wrote: > On Thu, 5 Nov 2026 at 10:44, Uladzislau Rezki wrote: > > > > @@ -1025,7 +1025,13 @@ void br_fdb_update(struct net_bridge *br, struct net_bridge_port *source, > > } > > } > > } else { > > - spin_lock(&br->hash_lock); > > + if (in_serving_softirq()) { > > + if (!spin_trylock(&br->hash_lock)) > > I don't think that in_serving_softirq() makes any sense. > > If I read this code correctly - and it's possible I didn't - this is > always called under local_bh_disable(). > > And local_bh_disable() will have increased the preempt-count exactly > so that it looks like it's in_serving_softirq(). > Sorry, probably i am missing something here. My understanding is that local_bh_disable() adds SOFTIRQ_DISABLE_OFFSET and in_serving_softirq() checks another SOFTIRQ_OFFSET bit. -- Uladzislau Rezki