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[24.6.151.244]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-71ec13eb642sm5323487b3a.179.2024.10.22.14.12.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 22 Oct 2024 14:12:40 -0700 (PDT) Date: Tue, 22 Oct 2024 14:12:38 -0700 From: Joe Damato To: netdev@vger.kernel.org, dmantipov@yandex.ru, Tony Nguyen , Przemek Kitszel , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , "moderated list:INTEL ETHERNET DRIVERS" , open list Subject: Re: [RFC iwl-net] e1000: Hold RTNL when e1000_down can be called Message-ID: Mail-Followup-To: Joe Damato , netdev@vger.kernel.org, dmantipov@yandex.ru, Tony Nguyen , Przemek Kitszel , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , "moderated list:INTEL ETHERNET DRIVERS" , open list References: <20241022172153.217890-1-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=us-ascii Content-Disposition: inline In-Reply-To: On Tue, Oct 22, 2024 at 01:00:47PM -0700, Joe Damato wrote: > On Tue, Oct 22, 2024 at 05:21:53PM +0000, Joe Damato wrote: > > e1000_down calls netif_queue_set_napi, which assumes that RTNL is held. > > > > There are a few paths for e1000_down to be called in e1000 where RTNL is > > not currently being held: > > - e1000_shutdown (pci shutdown) > > - e1000_suspend (power management) > > - e1000_reinit_locked (via e1000_reset_task delayed work) > > > > Hold RTNL in two places to fix this issue: > > - e1000_reset_task > > - __e1000_shutdown (which is called from both e1000_shutdown and > > e1000_suspend). > > It looks like there's one other spot I missed: > > e1000_io_error_detected (pci error handler) which should also hold > rtnl_lock: > > + if (netif_running(netdev)) { > + rtnl_lock(); > e1000_down(adapter); > + rtnl_unlock(); > + } > > I can send that update in the v2, but I'll wait to see if Intel has suggestions > on the below. > > > The other paths which call e1000_down seemingly hold RTNL and are OK: > > - e1000_close (ndo_stop) > > - e1000_change_mtu (ndo_change_mtu) > > > > I'm submitting this is as an RFC because: > > - the e1000_reinit_locked issue appears very similar to commit > > 21f857f0321d ("e1000e: add rtnl_lock() to e1000_reset_task"), which > > fixes a similar issue in e1000e > > > > however > > > > - adding rtnl to e1000_reinit_locked seemingly conflicts with an > > earlier e1000 commit b2f963bfaeba ("e1000: fix lockdep warning in > > e1000_reset_task"). > > > > Hopefully Intel can weigh in and shed some light on the correct way to > > go. Regarding the above locations where rtnl_lock may need to be held, comparing to other intel drivers: - e1000_reset_task: it appears that igc, igb, and e100e all hold rtnl_lock in their reset_task functions, so I think adding an rtnl_lock / rtnl_unlock to e1000_reset_task should be OK, despite the existence of commit b2f963bfaeba ("e1000: fix lockdep warning in e1000_reset_task"). - e1000_io_error_detected: - e1000e temporarily obtains and drops rtnl in e1000e_pm_freeze - ixgbe holds rtnl in the same path (toward the bottom of ixgbe_io_error_detected) - igb does NOT hold rtnl in this path (as far as I can tell) - it was suggested in another thread to hold rtnl in this path for igc [1]. Given that it will be added to igc and is held in this same path in e1000e and ixgbe, I think it is safe to add it for e1000, as well. - e1000_shutdown: - igb holds rtnl in the same path, - e1000e temporarily holds it in this path (via e1000e_pm_freeze) - ixgbe holds rtnl in the same path So based on the recommendation for igc [1], and the precedent set in the other Intel drivers in most cases (except igb and the io_error path), I think adding rtnl to all 3 locations described above is correct. Please let me know if you all agree. Thanks for reviewing this. [1]: https://lore.kernel.org/netdev/40242f59-139a-4b45-8949-1210039f881b@intel.com/