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[73.158.218.242]) by smtp.gmail.com with UTF8SMTPSA id 98e67ed59e1d1-3124e29f865sm1328221a91.7.2025.05.30.08.07.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 30 May 2025 08:07:30 -0700 (PDT) Date: Fri, 30 May 2025 08:07:29 -0700 From: Stanislav Fomichev To: Joe Damato Cc: netdev@vger.kernel.org, kuba@kernel.org, john.cs.hey@gmail.com, jacob.e.keller@intel.com, syzbot+846bb38dc67fe62cc733@syzkaller.appspotmail.com, Tony Nguyen , Przemek Kitszel , Andrew Lunn , "David S. Miller" , Eric Dumazet , Paolo Abeni , "moderated list:INTEL ETHERNET DRIVERS" , open list Subject: Re: [PATCH iwl-net] e1000: Move cancel_work_sync to avoid deadlock Message-ID: References: <20250530014949.215112-1-jdamato@fastly.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20250530014949.215112-1-jdamato@fastly.com> On 05/30, Joe Damato wrote: > Previously, e1000_down called cancel_work_sync for the e1000 reset task > (via e1000_down_and_stop), which takes RTNL. > > As reported by users and syzbot, a deadlock is possible due to lock > inversion in the following scenario: > > CPU 0: > - RTNL is held > - e1000_close > - e1000_down > - cancel_work_sync (takes the work queue mutex) > - e1000_reset_task > > CPU 1: > - process_one_work (takes the work queue mutex) > - e1000_reset_task (takes RTNL) nit: as Jakub mentioned in another thread, it seems more about the flush_work waiting for the reset_task to complete rather than wq mutexes (which are fake)? CPU 0: - RTNL is held - e1000_close - e1000_down - cancel_work_sync - __flush_work - CPU 1: - process_one_work - e1000_reset_task (takes RTNL) - The fix looks good! Acked-by: Stanislav Fomichev