From patchwork Tue Apr 26 22:10:26 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mathieu Poirier X-Patchwork-Id: 8946651 Return-Path: X-Original-To: patchwork-linux-arm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 6BFEC9F441 for ; Tue, 26 Apr 2016 22:14:15 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 6CC932013A for ; Tue, 26 Apr 2016 22:14:14 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.9]) (using TLSv1.2 with cipher AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 7697D200DE for ; Tue, 26 Apr 2016 22:14:13 +0000 (UTC) Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1avBDo-0004M4-Aw; Tue, 26 Apr 2016 22:12:44 +0000 Received: from mail-ig0-x22c.google.com ([2607:f8b0:4001:c05::22c]) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1avBCO-0002tA-9r for linux-arm-kernel@lists.infradead.org; Tue, 26 Apr 2016 22:11:17 +0000 Received: by mail-ig0-x22c.google.com with SMTP id u10so55978763igr.1 for ; Tue, 26 Apr 2016 15:10:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=p2Y568a7CoOTUCaP7uaiw5R9kchtn0IXBhPtFE5zSX4=; b=b+DmGDmtCDDjejLLan7sIHWHKyEEkpwFYJHaF1WPHF5+/Pi4PJIbiVI8GAQBJNi+tZ TN58kHGTS2blHe3hfXekqsSVv7bEb0hiYyZnjoiTFDNyeZX2yWR4FbRbF7M9GhBkLl6N AybQDmjGv2L/Ej+C49baP3XJaITqZYkJkArqo= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=p2Y568a7CoOTUCaP7uaiw5R9kchtn0IXBhPtFE5zSX4=; b=PXsOJFQO7sZ3DnShn5xunPdfoxBNMmdzpWPEN+1TuAKa9VbCXVKig0pBFi9eP640+u pvvVxGha2GT9VzCOk668dA7bf1+ghy/N6oh82Rws5GHY0abt0DfIgNI6h9Vf970qhIoS t22+yDtnW1Zsty97NVtegdAFokXLDRW2UaoWHAI/UHnamHAClzoWlkDaJepLWdYY8wiT CcXAKz0gvj/T7Rz4dSKr7oAHlFRM/1DVsnkRXlfYyKvISeUBox2QHBGqM8IDBPqyfkGa F5ry30h+MiIxTzUVLrZjT5CKUJVNgGfla9t1IMBr9UjzunpeONramQu6DZidoYd2YWSk +weQ== X-Gm-Message-State: AOPr4FW8C146hW5l4Rbe6Fpsofeah+3jzY69/z6AdKj0ncXyaLbNqWlVaO5hxiVuAFtTj6SZ X-Received: by 10.50.155.6 with SMTP id vs6mr21810002igb.79.1461708655402; Tue, 26 Apr 2016 15:10:55 -0700 (PDT) Received: from t430.cg.shawcable.net (S0106002369de4dac.cg.shawcable.net. [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 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> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20160426_151116_488634_F5A52B12 X-CRM114-Status: GOOD ( 17.68 ) X-Spam-Score: -2.7 (--) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-kernel@vger.kernel.org MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Spam-Status: No, score=-5.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, RCVD_IN_DNSWL_MED,RP_MATCHES_RCVD,T_DKIM_INVALID,UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP 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 Reviewed-by: Suzuki K Poulose --- 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(-) 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;