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Tue, 11 Aug 2020 08:52:04 -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: Ray Jui Message-ID: Date: Tue, 11 Aug 2020 08:52:00 -0700 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 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 > --- > drivers/i2c/busses/i2c-bcm-iproc.c | 13 ++++++++++++- > 1 file changed, 12 insertions(+), 1 deletion(-) > > diff --git a/drivers/i2c/busses/i2c-bcm-iproc.c b/drivers/i2c/busses/i2c-bcm-iproc.c > index 8a3c98866fb7..688e92818821 100644 > --- a/drivers/i2c/busses/i2c-bcm-iproc.c > +++ b/drivers/i2c/busses/i2c-bcm-iproc.c > @@ -1078,7 +1078,7 @@ static int bcm_iproc_i2c_unreg_slave(struct i2c_client *slave) > if (!iproc_i2c->slave) > return -EINVAL; > > - iproc_i2c->slave = NULL; > + disable_irq(iproc_i2c->irq); > > /* disable all slave interrupts */ > tmp = iproc_i2c_rd_reg(iproc_i2c, IE_OFFSET); > @@ -1091,6 +1091,17 @@ static int bcm_iproc_i2c_unreg_slave(struct i2c_client *slave) > tmp &= ~BIT(S_CFG_EN_NIC_SMB_ADDR3_SHIFT); > iproc_i2c_wr_reg(iproc_i2c, S_CFG_SMBUS_ADDR_OFFSET, tmp); > > + /* flush TX/RX FIFOs */ > + tmp = (BIT(S_FIFO_RX_FLUSH_SHIFT) | BIT(S_FIFO_TX_FLUSH_SHIFT)); > + iproc_i2c_wr_reg(iproc_i2c, S_FIFO_CTRL_OFFSET, tmp); > + > + /* clear all pending slave interrupts */ > + iproc_i2c_wr_reg(iproc_i2c, IS_OFFSET, ISR_MASK_SLAVE); > + > + iproc_i2c->slave = NULL; > + > + enable_irq(iproc_i2c->irq); > + > return 0; > } > > Thanks again, Dhananjay! Looks good to me. Acked-by: Ray Jui