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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Bart Van Assche <bvanassche@acm.org>,
        Dan Williams <dan.j.williams@intel.com>,
        Alexander Duyck <alexander.h.duyck@linux.intel.com>,
        Luis Chamberlain <mcgrof@kernel.org>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.20 123/352] driver core: Move async_synchronize_full call
Date:   Mon, 11 Feb 2019 15:15:50 +0100
Message-Id: <20190211141854.054167163@linuxfoundation.org>
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4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

[ Upstream commit c37d721c68ad88925ba0e72f6e14acb829a8c6bb ]

Move the async_synchronize_full call out of __device_release_driver and
into driver_detach.

The idea behind this is that the async_synchronize_full call will only
guarantee that any existing async operations are flushed. This doesn't do
anything to guarantee that a hotplug event that may occur while we are
doing the release of the driver will not be asynchronously scheduled.

By moving this into the driver_detach path we can avoid potential deadlocks
as we aren't holding the device lock at this point and we should not have
the driver we want to flush loaded so the flush will take care of any
asynchronous events the driver we are detaching might have scheduled.

Fixes: 765230b5f084 ("driver-core: add asynchronous probing support for drivers")
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/base/dd.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index dbba123e058d..9d6604b50d75 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -928,9 +928,6 @@ static void __device_release_driver(struct device *dev, struct device *parent)
 
 	drv = dev->driver;
 	if (drv) {
-		if (driver_allows_async_probing(drv))
-			async_synchronize_full();
-
 		while (device_links_busy(dev)) {
 			device_unlock(dev);
 			if (parent && dev->bus->need_parent_lock)
@@ -1036,6 +1033,9 @@ void driver_detach(struct device_driver *drv)
 	struct device_private *dev_prv;
 	struct device *dev;
 
+	if (driver_allows_async_probing(drv))
+		async_synchronize_full();
+
 	for (;;) {
 		spin_lock(&drv->p->klist_devices.k_lock);
 		if (list_empty(&drv->p->klist_devices.k_list)) {
-- 
2.19.1