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[68.147.8.254]) by smtp.gmail.com with ESMTPSA id zd17sm2684818igc.8.2016.04.26.15.10.53 (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Tue, 26 Apr 2016 15:10:54 -0700 (PDT) From: Mathieu Poirier To: linux-arm-kernel@lists.infradead.org, Suzuki.Poulose@arm.com Cc: linux-kernel@vger.kernel.org Subject: [PATCH V4 10/18] coresight: tmc: getting rid of multiple read access Date: Tue, 26 Apr 2016 16:10:26 -0600 Message-Id: <1461708634-6327-11-git-send-email-mathieu.poirier@linaro.org> X-Mailer: git-send-email 2.5.0 In-Reply-To: <1461708634-6327-1-git-send-email-mathieu.poirier@linaro.org> References: <1461708634-6327-1-git-send-email-mathieu.poirier@linaro.org> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Allowing multiple readers to access the trace data simultaniously via sysFS provides no shortage of opportunity for race condition, mandates two variable to be maintained (drvdata::read_count and drvdata::reading), makes the code complex and provide little advantages, if any. This patch streamlines the read process by restricting trace data access to a single user. That way drvdata::read_count can be eliminated and race conditions (along with faulty error handling) in function tmc_open() and tmc_release() eliminated. Signed-off-by: Mathieu Poirier --- drivers/hwtracing/coresight/coresight-tmc-etf.c | 5 +++++ drivers/hwtracing/coresight/coresight-tmc-etr.c | 4 ++++ drivers/hwtracing/coresight/coresight-tmc.c | 24 +++++++++--------------- drivers/hwtracing/coresight/coresight-tmc.h | 2 -- 4 files changed, 18 insertions(+), 17 deletions(-) -- 2.5.0 diff --git a/drivers/hwtracing/coresight/coresight-tmc-etf.c b/drivers/hwtracing/coresight/coresight-tmc-etf.c index 6eb1665cfc9c..60edf4d1968f 100644 --- a/drivers/hwtracing/coresight/coresight-tmc-etf.c +++ b/drivers/hwtracing/coresight/coresight-tmc-etf.c @@ -260,6 +260,11 @@ int tmc_read_prepare_etb(struct tmc_drvdata *drvdata) spin_lock_irqsave(&drvdata->spinlock, flags); + if (drvdata->reading) { + ret = -EBUSY; + goto out; + } + /* There is no point in reading a TMC in HW FIFO mode */ mode = readl_relaxed(drvdata->base + TMC_MODE); if (mode != TMC_MODE_CIRCULAR_BUFFER) { diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c index ac37bf904fb7..d6999b457fb8 100644 --- a/drivers/hwtracing/coresight/coresight-tmc-etr.c +++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c @@ -188,6 +188,10 @@ int tmc_read_prepare_etr(struct tmc_drvdata *drvdata) return -EINVAL; spin_lock_irqsave(&drvdata->spinlock, flags); + if (drvdata->reading) { + ret = -EBUSY; + goto out; + } /* If drvdata::buf is NULL the trace data has been read already */ if (drvdata->buf == NULL) { diff --git a/drivers/hwtracing/coresight/coresight-tmc.c b/drivers/hwtracing/coresight/coresight-tmc.c index e8e12a9b917a..ae7525a2b94a 100644 --- a/drivers/hwtracing/coresight/coresight-tmc.c +++ b/drivers/hwtracing/coresight/coresight-tmc.c @@ -95,7 +95,7 @@ static int tmc_read_prepare(struct tmc_drvdata *drvdata) return ret; } -static void tmc_read_unprepare(struct tmc_drvdata *drvdata) +static int tmc_read_unprepare(struct tmc_drvdata *drvdata) { int ret = 0; @@ -113,21 +113,20 @@ static void tmc_read_unprepare(struct tmc_drvdata *drvdata) if (!ret) dev_info(drvdata->dev, "TMC read end\n"); + + return ret; } static int tmc_open(struct inode *inode, struct file *file) { + int ret; struct tmc_drvdata *drvdata = container_of(file->private_data, struct tmc_drvdata, miscdev); - int ret = 0; - - if (drvdata->read_count++) - goto out; ret = tmc_read_prepare(drvdata); if (ret) return ret; -out: + nonseekable_open(inode, file); dev_dbg(drvdata->dev, "%s: successfully opened\n", __func__); @@ -167,19 +166,14 @@ static ssize_t tmc_read(struct file *file, char __user *data, size_t len, static int tmc_release(struct inode *inode, struct file *file) { + int ret; struct tmc_drvdata *drvdata = container_of(file->private_data, struct tmc_drvdata, miscdev); - if (--drvdata->read_count) { - if (drvdata->read_count < 0) { - dev_err(drvdata->dev, "mismatched close\n"); - drvdata->read_count = 0; - } - goto out; - } + ret = tmc_read_unprepare(drvdata); + if (ret) + return ret; - tmc_read_unprepare(drvdata); -out: dev_dbg(drvdata->dev, "%s: released\n", __func__); return 0; } diff --git a/drivers/hwtracing/coresight/coresight-tmc.h b/drivers/hwtracing/coresight/coresight-tmc.h index df661903f83c..592eb149fe3a 100644 --- a/drivers/hwtracing/coresight/coresight-tmc.h +++ b/drivers/hwtracing/coresight/coresight-tmc.h @@ -94,7 +94,6 @@ enum tmc_mem_intf_width { * @csdev: component vitals needed by the framework. * @miscdev: specifics to handle "/dev/xyz.tmc" entry. * @spinlock: only one at a time pls. - * @read_count: manages preparation of buffer for reading. * @buf: area of memory where trace data get sent. * @paddr: DMA start location in RAM. * @vaddr: virtual representation of @paddr. @@ -109,7 +108,6 @@ struct tmc_drvdata { struct coresight_device *csdev; struct miscdevice miscdev; spinlock_t spinlock; - int read_count; bool reading; char *buf; dma_addr_t paddr;