From: SeongJae Park <sjpark@amazon.com>
To: <jgross@suse.com>, <axboe@kernel.dk>, <konrad.wilk@oracle.com>,
<roger.pau@citrix.com>
Cc: linux-block@vger.kernel.org, sjpark@amazon.com,
pdurrant@amazon.com, SeongJae Park <sjpark@amazon.de>,
linux-kernel@vger.kernel.org, sj38.park@gmail.com,
xen-devel@lists.xenproject.org
Subject: [Xen-devel] [PATCH v11 2/6] xenbus/backend: Protect xenbus callback with lock
Date: Tue, 17 Dec 2019 17:07:44 +0100 [thread overview]
Message-ID: <20191217160748.693-3-sjpark@amazon.com> (raw)
In-Reply-To: <20191217160748.693-1-sjpark@amazon.com>
From: SeongJae Park <sjpark@amazon.de>
'reclaim_memory' callback can race with a driver code as this callback
will be called from any memory pressure detected context. To deal with
the case, this commit adds a spinlock in the 'xenbus_device'. Whenever
'reclaim_memory' callback is called, the lock of the device which passed
to the callback as its argument is locked. Thus, drivers registering
their 'reclaim_memory' callback should protect the data that might race
with the callback with the lock by themselves.
Signed-off-by: SeongJae Park <sjpark@amazon.de>
---
drivers/xen/xenbus/xenbus_probe.c | 1 +
drivers/xen/xenbus/xenbus_probe_backend.c | 10 ++++++++--
include/xen/xenbus.h | 2 ++
3 files changed, 11 insertions(+), 2 deletions(-)
diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c
index 5b471889d723..b86393f172e6 100644
--- a/drivers/xen/xenbus/xenbus_probe.c
+++ b/drivers/xen/xenbus/xenbus_probe.c
@@ -472,6 +472,7 @@ int xenbus_probe_node(struct xen_bus_type *bus,
goto fail;
dev_set_name(&xendev->dev, "%s", devname);
+ spin_lock_init(&xendev->reclaim_lock);
/* Register with generic device framework. */
err = device_register(&xendev->dev);
diff --git a/drivers/xen/xenbus/xenbus_probe_backend.c b/drivers/xen/xenbus/xenbus_probe_backend.c
index 7e78ebef7c54..516aa64b9967 100644
--- a/drivers/xen/xenbus/xenbus_probe_backend.c
+++ b/drivers/xen/xenbus/xenbus_probe_backend.c
@@ -251,12 +251,18 @@ static int backend_probe_and_watch(struct notifier_block *notifier,
static int backend_reclaim_memory(struct device *dev, void *data)
{
const struct xenbus_driver *drv;
+ struct xenbus_device *xdev;
+ unsigned long flags;
if (!dev->driver)
return 0;
drv = to_xenbus_driver(dev->driver);
- if (drv && drv->reclaim_memory)
- drv->reclaim_memory(to_xenbus_device(dev));
+ if (drv && drv->reclaim_memory) {
+ xdev = to_xenbus_device(dev);
+ spin_trylock_irqsave(&xdev->reclaim_lock, flags);
+ drv->reclaim_memory(xdev);
+ spin_unlock_irqrestore(&xdev->reclaim_lock, flags);
+ }
return 0;
}
diff --git a/include/xen/xenbus.h b/include/xen/xenbus.h
index c861cfb6f720..d9468313061d 100644
--- a/include/xen/xenbus.h
+++ b/include/xen/xenbus.h
@@ -76,6 +76,8 @@ struct xenbus_device {
enum xenbus_state state;
struct completion down;
struct work_struct work;
+ /* 'reclaim_memory' callback is called while this lock is acquired */
+ spinlock_t reclaim_lock;
};
static inline struct xenbus_device *to_xenbus_device(struct device *dev)
--
2.17.1
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next prev parent reply other threads:[~2019-12-17 16:08 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-17 16:07 [Xen-devel] [PATCH v11 0/6] xenbus/backend: Add a memory pressure handler callback SeongJae Park
2019-12-17 16:07 ` [Xen-devel] [PATCH v11 1/6] xenbus/backend: Add " SeongJae Park
2019-12-17 16:07 ` SeongJae Park [this message]
2019-12-17 16:13 ` [Xen-devel] [PATCH v11 2/6] xenbus/backend: Protect xenbus callback with lock Jürgen Groß
2019-12-17 16:24 ` SeongJae Park
2019-12-17 17:10 ` Jürgen Groß
2019-12-17 17:27 ` SeongJae Park
2019-12-17 16:07 ` [Xen-devel] [PATCH v11 3/6] xen/blkback: Squeeze page pools if a memory pressure is detected SeongJae Park
2019-12-17 16:07 ` [Xen-devel] [PATCH v11 4/6] xen/blkback: Protect 'reclaim_memory()' with 'reclaim_lock' SeongJae Park
2019-12-17 16:15 ` Jürgen Groß
2019-12-17 16:31 ` [Xen-devel] [PATCH 1/3] xen/blkback: Squeeze page pools if a memory pressure is detected SeongJae Park
2019-12-17 16:10 ` [Xen-devel] [PATCH v11 5/6] xen/blkback: Remove unnecessary static variable name prefixes SeongJae Park
2019-12-17 16:10 ` [Xen-devel] [PATCH v11 6/6] xen/blkback: Consistently insert one empty line between functions SeongJae Park
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