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smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=CZXtbGi8; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 07709606A31A for ; Fri, 30 Oct 2026 12:23:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=CZXtbGi8 Received: by smtp.kernel.org (Postfix) with ESMTPSA id DDE761F000C1; Fri, 30 Oct 2026 12:23:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793363010; bh=6lG9R4lJJPALXaPZSnu7JMLL8FE4c58m/VBFEDfgMwM=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=CZXtbGi8RUOcHn3Nk0VxGeJCgtXUC60eLfbKUaZmEDjndHKvUIm9tFHo++B1Ynhhb hGunlzO2jAKFUDlSnFUfb5XwF/av7rwQg4KEcCQPO6YnWIRn7RZHMWdbr9kofx+kmh tgiiF0rL4H9zR7bG59z+Ki8IXjV0Oy0ci+URtGCFyD25c8zMKDBUED82kW2MYopcfU LWIL9OPh+QmsqHR7BcB0a6up+/jUVNqtkSgTh2hrRzEjrd+NURbTbYYJTG+4eufadQ sc/XnkOgeqqJF45hHUo0142yyME3aOQcCClB0j7hE7VyZeHEDZNx9QALB6153ai9zj SyzP2RjgtLqAQ== Message-ID: <34280aad-a01e-4f84-ada7-c715b2958cb1@kernel.org> Date: Fri, 30 Oct 2026 13:23:27 +0100 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/9] w1: use the bus mutex for the "rw" file To: Greg Kroah-Hartman Cc: Josef Bacik , linux-kernel@vger.kernel.org, stable References: <20261027-llm-char-misc-w1-v1-0-d2e6bfafb6a4@linuxfoundation.org> <20261027-llm-char-misc-w1-v1-1-d2e6bfafb6a4@linuxfoundation.org> From: Krzysztof Kozlowski Content-Language: en-US Autocrypt: addr=krzk@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 27/10/2026 17:04, Greg Kroah-Hartman wrote: > From: Josef Bacik > > Commit b02f8bede217 ("W1: split master mutex to avoid deadlocks.") gave > the bus a mutex of its own, because the lock which protects the list of > slaves is held while a slave is removed, which waits for the sysfs > callbacks of the slave, so these must not take it. It converted all the > slave drivers, but not the "rw" file of the default family in w1.c, > which still takes the mutex of the master to talk on the bus. That has > two consequences: > > - A deadlock. w1_process() holds the mutex of the master while it > searches the bus and detaches the slaves which have gone: > > w1_process() read() of .../rw > mutex_lock(&dev->mutex) kernfs active reference > w1_search_process() rw_read() > w1_slave_detach() mutex_lock(&master->mutex) > w1_unref_slave() waits > device_unregister() > waits for the reference > > The file is readable for everybody. > > - The accesses through this file are not serialised with those of the > slave drivers, which take bus_mutex, so that two transactions can get > mixed up on the wire. > > Take bus_mutex here as well. It also excludes the search, which takes it > for every pass. > > Fixes: b02f8bede217 ("W1: split master mutex to avoid deadlocks.") > Cc: stable > Signed-off-by: Josef Bacik > Signed-off-by: Greg Kroah-Hartman Reviewed-by: Krzysztof Kozlowski Best regards, Krzysztof