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ABdhPJz1iCqheRbCE5aOpUzM8RcqYE6DlFWc8YWxT0t59CFmQF8oFulh6fPsawfQwWwC4maM8uGT9w== X-Received: by 2002:a17:906:194b:: with SMTP id b11mr54746825eje.28.1594382752559; Fri, 10 Jul 2020 05:05:52 -0700 (PDT) Received: from BV030612LT ([188.24.137.55]) by smtp.gmail.com with ESMTPSA id cw19sm3552701ejb.39.2020.07.10.05.05.51 (version=TLS1_2 cipher=ECDHE-ECDSA-CHACHA20-POLY1305 bits=256/256); Fri, 10 Jul 2020 05:05:51 -0700 (PDT) Date: Fri, 10 Jul 2020 15:05:49 +0300 From: Cristian Ciocaltea To: Greg Kroah-Hartman Cc: Andreas =?iso-8859-1?Q?F=E4rber?= , Manivannan Sadhasivam , Jiri Slaby , Andy Shevchenko , linux-serial@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-actions@lists.infradead.org Subject: Re: [PATCH 1/1] tty: serial: owl: Initialize lock before registering port Message-ID: <20200710120549.GA11293@BV030612LT> References: <89f6393934fc6d493f8b9e87c1a6e916642b6a18.1590749143.git.cristian.ciocaltea@gmail.com> <20200529113419.GA1631227@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200529113419.GA1631227@kroah.com> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, May 29, 2020 at 01:34:19PM +0200, Greg Kroah-Hartman wrote: > On Fri, May 29, 2020 at 02:06:47PM +0300, Cristian Ciocaltea wrote: > > Running a lockdep-enabled kernel leads to the following splat when > > probing the owl-uart driver: > > > > [ 1.271784] b0124000.serial: ttyOWL2 at MMIO 0xb0124000 (irq = 22, base_baud = 1500000) is a owl-uart > > [ 1.281226] INFO: trying to register non-static key. > > [ 1.286179] the code is fine but needs lockdep annotation. > > [ 1.291648] turning off the locking correctness validator. > > [ 1.297125] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.7.0-rc7+ #70 > > [ 1.303462] Hardware name: Generic DT based system > > [ 1.308268] [<80111d3c>] (unwind_backtrace) from [<8010c9b8>] (show_stack+0x10/0x14) > > [ 1.316003] [<8010c9b8>] (show_stack) from [<805016b4>] (dump_stack+0xb4/0xe0) > > [ 1.323218] [<805016b4>] (dump_stack) from [<80182dec>] (register_lock_class+0x25c/0x8f4) > > [ 1.331391] [<80182dec>] (register_lock_class) from [<8017ee34>] (__lock_acquire+0xb4/0x2ee4) > > [ 1.339901] [<8017ee34>] (__lock_acquire) from [<8018291c>] (lock_acquire+0x424/0x4c8) > > [ 1.347813] [<8018291c>] (lock_acquire) from [<808597b0>] (_raw_spin_lock_irqsave+0x54/0x68) > > [ 1.356242] [<808597b0>] (_raw_spin_lock_irqsave) from [<80582e94>] (uart_add_one_port+0x384/0x510) > > [ 1.365276] [<80582e94>] (uart_add_one_port) from [<8058b4d0>] (owl_uart_probe+0x1bc/0x248) > > [ 1.373621] [<8058b4d0>] (owl_uart_probe) from [<8059c0e4>] (platform_drv_probe+0x48/0x94) > > [ 1.381874] [<8059c0e4>] (platform_drv_probe) from [<805997c4>] (really_probe+0x200/0x470) > > [ 1.390123] [<805997c4>] (really_probe) from [<80599c80>] (driver_probe_device+0x16c/0x1bc) > > [ 1.398461] [<80599c80>] (driver_probe_device) from [<80599f18>] (device_driver_attach+0x44/0x60) > > [ 1.407317] [<80599f18>] (device_driver_attach) from [<8059a078>] (__driver_attach+0x144/0x14c) > > [ 1.416000] [<8059a078>] (__driver_attach) from [<805978ac>] (bus_for_each_dev+0x5c/0xb4) > > [ 1.424162] [<805978ac>] (bus_for_each_dev) from [<8059896c>] (bus_add_driver+0x118/0x204) > > [ 1.432410] [<8059896c>] (bus_add_driver) from [<8059ae6c>] (driver_register+0xbc/0xf8) > > [ 1.440405] [<8059ae6c>] (driver_register) from [<80c1fd24>] (owl_uart_init+0x20/0x40) > > [ 1.448313] [<80c1fd24>] (owl_uart_init) from [<801021d8>] (do_one_initcall+0x184/0x3a4) > > [ 1.456399] [<801021d8>] (do_one_initcall) from [<80c01100>] (kernel_init_freeable+0x264/0x2e4) > > [ 1.465085] [<80c01100>] (kernel_init_freeable) from [<80850a88>] (kernel_init+0x8/0x110) > > [ 1.473249] [<80850a88>] (kernel_init) from [<80100114>] (ret_from_fork+0x14/0x20) > > [ 1.480800] Exception stack(0xee8bdfb0 to 0xee8bdff8) > > [ 1.485841] dfa0: 00000000 00000000 00000000 00000000 > > [ 1.494002] dfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 > > [ 1.502162] dfe0: 00000000 00000000 00000000 00000000 00000013 00000000 > > [ 1.508914] printk: console [ttyOWL2] enabled > > > > The locking issue occurs in uart_configure_port() when trying to > > guard the call to set_mctrl(). > > > > uart_add_one_port() should normally initialize the spinlock via > > uart_port_spin_lock_init(), but it never happens because the port is > > detected as a console and, as a consequence, the spinlock is expected > > to be already initialized. > > > > The commit a3cb39d258ef > > ("serial: core: Allow detach and attach serial device for console") > > changed the lock initialization logic to assume the spinlock is > > initialized even if the console is not enabled. > > > > Therefore, initialize the lock explicitly in owl_uart_probe(), before > > attempting to invoke uart_add_one_port(). > > > > Fixes: a3cb39d258ef ("serial: core: Allow detach and attach serial device for console") > > Signed-off-by: Cristian Ciocaltea > > --- > > drivers/tty/serial/owl-uart.c | 2 ++ > > 1 file changed, 2 insertions(+) > > > > diff --git a/drivers/tty/serial/owl-uart.c b/drivers/tty/serial/owl-uart.c > > index c149f8c30007..c2fa2f15d50a 100644 > > --- a/drivers/tty/serial/owl-uart.c > > +++ b/drivers/tty/serial/owl-uart.c > > @@ -705,6 +705,8 @@ static int owl_uart_probe(struct platform_device *pdev) > > owl_uart_ports[pdev->id] = owl_port; > > platform_set_drvdata(pdev, owl_port); > > > > + spin_lock_init(&owl_port->port.lock); > > + > > ret = uart_add_one_port(&owl_uart_driver, &owl_port->port); > > if (ret) > > owl_uart_ports[pdev->id] = NULL; > > Ugh, another one :( > > Thanks for this, will queue this up now. > > greg k-h Hi Greg, I think this was mistakenly omitted from the inclusion in v5.8, or has it been postponed for v5.9? Thanks, Cristi