linux-kernel - [PATCH v4 05/14] coresight: get/put module in coresight_build/release

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Date:   Tue,  5 Jun 2018 16:07:01 -0500
From:   Kim Phillips <kim.phillips@....com>
To:     Mathieu Poirier <mathieu.poirier@...aro.org>
Cc:     Leo Yan <leo.yan@...aro.org>,
        Suzuki K Poulose <Suzuki.Poulose@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Howells <dhowells@...hat.com>,
        Eric Auger <eric.auger@...hat.com>,
        Eric Biederman <ebiederm@...ssion.com>,
        Gargi Sharma <gs051095@...il.com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Kefeng Wang <wangkefeng.wang@...wei.com>,
        Kirill Tkhai <ktkhai@...tuozzo.com>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        Oleg Nesterov <oleg@...hat.com>,
        Pavel Tatashin <pasha.tatashin@...cle.com>,
        Rik van Riel <riel@...hat.com>,
        Robin Murphy <robin.murphy@....com>,
        Russell King <linux@...linux.org.uk>,
        Thierry Reding <treding@...dia.com>,
        Todd Kjos <tkjos@...gle.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Kim Phillips <kim.phillips@....com>
Subject: [PATCH v4 05/14] coresight: get/put module in coresight_build/release_path

Increment the refcnt for driver modules in current use by calling
module_get in coresight_build_path and module_put in release_path.

This prevents driver modules from being unloaded when they are in use,
either in sysfs or perf mode.

Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
Cc: Leo Yan <leo.yan@...aro.org>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Randy Dunlap <rdunlap@...radead.org>
Cc: Suzuki K Poulose <Suzuki.Poulose@....com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Russell King <linux@...linux.org.uk>
Signed-off-by: Kim Phillips <kim.phillips@....com>
---
 drivers/hwtracing/coresight/coresight.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/hwtracing/coresight/coresight.c b/drivers/hwtracing/coresight/coresight.c
index 338f1719641c..1c941351f1d1 100644
--- a/drivers/hwtracing/coresight/coresight.c
+++ b/drivers/hwtracing/coresight/coresight.c
@@ -465,6 +465,12 @@ static int _coresight_build_path(struct coresight_device *csdev,
 
 	node->csdev = csdev;
 	list_add(&node->link, path);
+
+	if (!try_module_get(csdev->dev.parent->driver->owner)) {
+		dev_err(&csdev->dev, "could not get coresight driver module\n");
+		return -ENODEV;
+	}
+
 	pm_runtime_get_sync(csdev->dev.parent);
 
 	return 0;
@@ -510,6 +516,9 @@ void coresight_release_path(struct list_head *path)
 		csdev = nd->csdev;
 
 		pm_runtime_put_sync(csdev->dev.parent);
+
+		module_put(csdev->dev.parent->driver->owner);
+
 		list_del(&nd->link);
 		kfree(nd);
 	}
-- 
2.17.0