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Mon, 10 Aug 2020 19:31:02 -0700 (PDT) Subject: Re: [PATCH v3] i2c: iproc: fix race between client unreg and isr To: Dhananjay Phadke , linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org, Wolfram Sang , Ray Jui Cc: Rayagonda Kokatanur , bcm-kernel-feedback-list@broadcom.com References: <1597106560-79693-1-git-send-email-dphadke@linux.microsoft.com> From: Florian Fainelli Message-ID: <69576821-1e8e-51c2-6c15-5774ca598c36@gmail.com> Date: Mon, 10 Aug 2020 19:30:58 -0700 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Firefox/68.0 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <1597106560-79693-1-git-send-email-dphadke@linux.microsoft.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-i2c-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-i2c@vger.kernel.org On 8/10/2020 5:42 PM, Dhananjay Phadke wrote: > When i2c client unregisters, synchronize irq before setting > iproc_i2c->slave to NULL. > > (1) disable_irq() > (2) Mask event enable bits in control reg > (3) Erase slave address (avoid further writes to rx fifo) > (4) Flush tx and rx FIFOs > (5) Clear pending event (interrupt) bits in status reg > (6) enable_irq() > (7) Set client pointer to NULL > > Unable to handle kernel NULL pointer dereference at virtual address 0000000000000318 > > [ 371.020421] pc : bcm_iproc_i2c_isr+0x530/0x11f0 > [ 371.025098] lr : __handle_irq_event_percpu+0x6c/0x170 > [ 371.030309] sp : ffff800010003e40 > [ 371.033727] x29: ffff800010003e40 x28: 0000000000000060 > [ 371.039206] x27: ffff800010ca9de0 x26: ffff800010f895df > [ 371.044686] x25: ffff800010f18888 x24: ffff0008f7ff3600 > [ 371.050165] x23: 0000000000000003 x22: 0000000001600000 > [ 371.055645] x21: ffff800010f18888 x20: 0000000001600000 > [ 371.061124] x19: ffff0008f726f080 x18: 0000000000000000 > [ 371.066603] x17: 0000000000000000 x16: 0000000000000000 > [ 371.072082] x15: 0000000000000000 x14: 0000000000000000 > [ 371.077561] x13: 0000000000000000 x12: 0000000000000001 > [ 371.083040] x11: 0000000000000000 x10: 0000000000000040 > [ 371.088519] x9 : ffff800010f317c8 x8 : ffff800010f317c0 > [ 371.093999] x7 : ffff0008f805b3b0 x6 : 0000000000000000 > [ 371.099478] x5 : ffff0008f7ff36a4 x4 : ffff8008ee43d000 > [ 371.104957] x3 : 0000000000000000 x2 : ffff8000107d64c0 > [ 371.110436] x1 : 00000000c00000af x0 : 0000000000000000 > > [ 371.115916] Call trace: > [ 371.118439] bcm_iproc_i2c_isr+0x530/0x11f0 > [ 371.122754] __handle_irq_event_percpu+0x6c/0x170 > [ 371.127606] handle_irq_event_percpu+0x34/0x88 > [ 371.132189] handle_irq_event+0x40/0x120 > [ 371.136234] handle_fasteoi_irq+0xcc/0x1a0 > [ 371.140459] generic_handle_irq+0x24/0x38 > [ 371.144594] __handle_domain_irq+0x60/0xb8 > [ 371.148820] gic_handle_irq+0xc0/0x158 > [ 371.152687] el1_irq+0xb8/0x140 > [ 371.155927] arch_cpu_idle+0x10/0x18 > [ 371.159615] do_idle+0x204/0x290 > [ 371.162943] cpu_startup_entry+0x24/0x60 > [ 371.166990] rest_init+0xb0/0xbc > [ 371.170322] arch_call_rest_init+0xc/0x14 > [ 371.174458] start_kernel+0x404/0x430 > > Fixes: c245d94ed106 ("i2c: iproc: Add multi byte read-write support for slave mode") > > Signed-off-by: Dhananjay Phadke Reviewed-by: Florian Fainelli -- Florian