From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Wang, Haiyue" Subject: Re: [PATCH i2c/slave-mqueue v5] i2c: slave-mqueue: add a slave backend to receive and queue messages Date: Thu, 30 May 2019 09:39:05 +0800 Message-ID: References: <1524503192-4176-1-git-send-email-haiyue.wang@linux.intel.com> <20190523220345.GA3417@u40b0340c692b58f6553c.ant.amazon.com> <35a9d066-c732-cb00-04a5-438c948915ae@linux.intel.com> <20190524173353.GA6428@u40b0340c692b58f6553c.ant.amazon.com> <20190529231100.GA18339@u40b0340c692b58f6553c.ant.amazon.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <20190529231100.GA18339@u40b0340c692b58f6553c.ant.amazon.com> Sender: linux-kernel-owner@vger.kernel.org To: Eduardo Valentin Cc: wsa@the-dreams.de, brendanhiggins@google.com, linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org, openbmc@lists.ozlabs.org, jarkko.nikula@linux.intel.com, andriy.shevchenko@intel.com, jae.hyun.yoo@linux.intel.com List-Id: linux-i2c@vger.kernel.org 在 2019-05-30 07:11, Eduardo Valentin 写道: >>> this code goes access and modify data here, e.g. msg->len and msg->buf. >>> >>> On this case (I2C_SLAVE_WRITE_RECEIVED), this code wont protect access. >>> >>> This can cause concurrence issues if you receive an IRQ when the user >>> is on your bin_read(). >> User will not touch 'msg = mq->curr;', just touch 'msg = >> &mq->queue[mq->out];' > What happens if mq->curr == mq->queue[mq->out]? > 1. The Read will check. + spin_lock_irqsave(&mq->lock, flags); + if (mq->out != mq->in) { + msg = &mq->queue[mq->out]; 2. Flush the oldeast message. ^_^ + case I2C_SLAVE_STOP: + if (unlikely(mq->truncated || msg->len < 2)) + break; + + spin_lock(&mq->lock); + mq->in = MQ_QUEUE_NEXT(mq->in); + mq->curr = &mq->queue[mq->in]; + mq->curr->len = 0; + + /* Flush the oldest message */ + if (mq->out == mq->in) + mq->out = MQ_QUEUE_NEXT(mq->out); + spin_unlock(&mq->lock);