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Thu, 16 Apr 2020 10:40:27 +0100 Date: Thu, 16 Apr 2020 10:40:25 +0100 From: Marc Zyngier To: Jerome Brunet Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Thomas Gleixner , Jason Cooper , Kevin Hilman , Martin Blumenstingl Subject: Re: [PATCH] irqchip/meson-gpio: Fix HARDIRQ-safe -> HARDIRQ-unsafe lock order Message-ID: <20200416104025.5a22c228@why> In-Reply-To: <1jeesqt686.fsf@starbuckisacylon.baylibre.com> References: <20200407144658.829246-1-maz@kernel.org> <20200414142018.6e7e5ec3@why> <1jeesqt686.fsf@starbuckisacylon.baylibre.com> Organization: Approximate X-Mailer: Claws Mail 3.17.5 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-SA-Exim-Connect-IP: 62.31.163.78 X-SA-Exim-Rcpt-To: jbrunet@baylibre.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, tglx@linutronix.de, jason@lakedaemon.net, khilman@baylibre.com, martin.blumenstingl@googlemail.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 14 Apr 2020 17:52:25 +0200 Jerome Brunet wrote: Hi Jerome, > On Tue 14 Apr 2020 at 15:20, Marc Zyngier wrote: > > > On Tue, 7 Apr 2020 15:46:58 +0100 > > Marc Zyngier wrote: > > > > +Jerome, Martin, > > > >> Running a lockedp-enabled kernel on a vim3l board (Amlogic SM1) > >> leads to the following splat: > >> > >> [ 13.557138] WARNING: HARDIRQ-safe -> HARDIRQ-unsafe lock order detected > >> [ 13.587485] ip/456 [HC0[0]:SC0[0]:HE0:SE1] is trying to acquire: > >> [ 13.625922] ffff000059908cf0 (&irq_desc_lock_class){-.-.}-{2:2}, at: __setup_irq+0xf8/0x8d8 > >> [ 13.632273] which would create a new lock dependency: > >> [ 13.637272] (&irq_desc_lock_class){-.-.}-{2:2} -> (&ctl->lock){+.+.}-{2:2} > >> [ 13.644209] > >> [ 13.644209] but this new dependency connects a HARDIRQ-irq-safe lock: > >> [ 13.654122] (&irq_desc_lock_class){-.-.}-{2:2} > >> [ 13.654125] > >> [ 13.654125] ... which became HARDIRQ-irq-safe at: > >> [ 13.664759] lock_acquire+0xec/0x368 > >> [ 13.666926] _raw_spin_lock+0x60/0x88 > >> [ 13.669979] handle_fasteoi_irq+0x30/0x178 > >> [ 13.674082] generic_handle_irq+0x38/0x50 > >> [ 13.678098] __handle_domain_irq+0x6c/0xc8 > >> [ 13.682209] gic_handle_irq+0x5c/0xb0 > >> [ 13.685872] el1_irq+0xd0/0x180 > >> [ 13.689010] arch_cpu_idle+0x40/0x220 > >> [ 13.692732] default_idle_call+0x54/0x60 > >> [ 13.696677] do_idle+0x23c/0x2e8 > >> [ 13.699903] cpu_startup_entry+0x30/0x50 > >> [ 13.703852] rest_init+0x1e0/0x2b4 > >> [ 13.707301] arch_call_rest_init+0x18/0x24 > >> [ 13.711449] start_kernel+0x4ec/0x51c > >> [ 13.715167] > >> [ 13.715167] to a HARDIRQ-irq-unsafe lock: > >> [ 13.722426] (&ctl->lock){+.+.}-{2:2} > >> [ 13.722430] > >> [ 13.722430] ... which became HARDIRQ-irq-unsafe at: > >> [ 13.732319] ... > >> [ 13.732324] lock_acquire+0xec/0x368 > >> [ 13.735985] _raw_spin_lock+0x60/0x88 > >> [ 13.739452] meson_gpio_irq_domain_alloc+0xcc/0x290 > >> [ 13.744392] irq_domain_alloc_irqs_hierarchy+0x24/0x60 > >> [ 13.749586] __irq_domain_alloc_irqs+0x160/0x2f0 > >> [ 13.754254] irq_create_fwspec_mapping+0x118/0x320 > >> [ 13.759073] irq_create_of_mapping+0x78/0xa0 > >> [ 13.763360] of_irq_get+0x6c/0x80 > >> [ 13.766701] of_mdiobus_register_phy+0x10c/0x238 [of_mdio] > >> [ 13.772227] of_mdiobus_register+0x158/0x380 [of_mdio] > >> [ 13.777388] mdio_mux_init+0x180/0x2e8 [mdio_mux] > >> [ 13.782128] g12a_mdio_mux_probe+0x290/0x398 [mdio_mux_meson_g12a] > >> [ 13.788349] platform_drv_probe+0x5c/0xb0 > >> [ 13.792379] really_probe+0xe4/0x448 > >> [ 13.795979] driver_probe_device+0xe8/0x140 > >> [ 13.800189] __device_attach_driver+0x94/0x120 > >> [ 13.804639] bus_for_each_drv+0x84/0xd8 > >> [ 13.808474] __device_attach+0xe4/0x168 > >> [ 13.812361] device_initial_probe+0x1c/0x28 > >> [ 13.816592] bus_probe_device+0xa4/0xb0 > >> [ 13.820430] deferred_probe_work_func+0xa8/0x100 > >> [ 13.825064] process_one_work+0x264/0x688 > >> [ 13.829088] worker_thread+0x4c/0x458 > >> [ 13.832768] kthread+0x154/0x158 > >> [ 13.836018] ret_from_fork+0x10/0x18 > >> [ 13.839612] > >> [ 13.839612] other info that might help us debug this: > >> [ 13.839612] > >> [ 13.850354] Possible interrupt unsafe locking scenario: > >> [ 13.850354] > >> [ 13.855720] CPU0 CPU1 > >> [ 13.858774] ---- ---- > >> [ 13.863242] lock(&ctl->lock); > >> [ 13.866330] local_irq_disable(); > >> [ 13.872233] lock(&irq_desc_lock_class); > >> [ 13.878705] lock(&ctl->lock); > >> [ 13.884297] > >> [ 13.886857] lock(&irq_desc_lock_class); > >> [ 13.891014] > >> [ 13.891014] *** DEADLOCK *** > >> > >> The issue can occur when CPU1 is doing something like irq_set_type() > >> and CPU0 performing an interrupt allocation, for example. Taking > >> an interrupt (like the one being reconfigured) would lead to a > >> deadlock. > > Just to make sure I understand > * the 1st trace is a CPU getting interrupted while setting the irq type > * the 2nd trace is another CPU trying to allocate an irq for network PHY. The traces are only what lockdep sees as a dangerous behaviour, not necessarily what actually leads to a deadlock. The deadlock scenario is the one outlined just before "*** DEADLOCK ***", and a way to get there is my interpretation just above. > >> > >> A solution to this is: > >> > >> - Reorder the locking so that meson_gpio_irq_update_bits takes the lock > >> itself at all times, instead of relying on the caller to lock or not, > >> hence making the RMW sequence atomic, > >> > >> - Rework the critical section in meson_gpio_irq_request_channel to only > >> cover the allocation itself, and let the gpio_irq_sel_pin callback > >> deal with its own locking if required, > >> > >> - Take the private spin-lock with interrupts disabled at all times > > Looks like the only safe path if I understand correctly. > The patch below looks good to me. > > >> > >> Signed-off-by: Marc Zyngier > > Thanks for the fix Marc. > > Reviewed-by: Jerome Brunet Thanks, M. -- Jazz is not dead. It just smells funny...