6.11-stable review patch. If anyone has any objections, please let me know.
------------------
From: Dan Williams <dan.j.williams@xxxxxxxxx>
[ Upstream commit 3d6ebf16438de5d712030fefbb4182b46373d677 ]
It turns out since its original introduction, pre-2.6.12,
bus_rescan_devices() has skipped devices that might be in the process of
attaching or detaching from their driver. For CXL this behavior is
unwanted and expects that cxl_bus_rescan() is a probe barrier.
That behavior is simple enough to achieve with bus_for_each_dev() paired
with call to device_attach(), and it is unclear why bus_rescan_devices()
took the position of lockless consumption of dev->driver which is racy.
The "Fixes:" but no "Cc: stable" on this patch reflects that the issue
is merely by inspection since the bug that triggered the discovery of
this potential problem [1] is fixed by other means. However, a stable
backport should do no harm.
Fixes: 8dd2bc0f8e02 ("cxl/mem: Add the cxl_mem driver")
Link: http://lore.kernel.org/20241004212504.1246-1-gourry@xxxxxxxxxx [1]
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Tested-by: Gregory Price <gourry@xxxxxxxxxx>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
Reviewed-by: Ira Weiny <ira.weiny@xxxxxxxxx>
Link: https://patch.msgid.link/172964781104.81806.4277549800082443769.stgit@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Ira Weiny <ira.weiny@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
drivers/cxl/core/port.c | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)
diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
index 1d5007e3795a3..d3237346f6877 100644
--- a/drivers/cxl/core/port.c
+++ b/drivers/cxl/core/port.c
@@ -2088,11 +2088,18 @@ static void cxl_bus_remove(struct device *dev)
static struct workqueue_struct *cxl_bus_wq;
-static void cxl_bus_rescan_queue(struct work_struct *w)
+static int cxl_rescan_attach(struct device *dev, void *data)
{
- int rc = bus_rescan_devices(&cxl_bus_type);
+ int rc = device_attach(dev);
+
+ dev_vdbg(dev, "rescan: %s\n", rc ? "attach" : "detached");
- pr_debug("CXL bus rescan result: %d\n", rc);
+ return 0;
+}
+
+static void cxl_bus_rescan_queue(struct work_struct *w)
+{
+ bus_for_each_dev(&cxl_bus_type, NULL, NULL, cxl_rescan_attach);
}
void cxl_bus_rescan(void)
--
2.43.0
