Inside bus_add_driver(), one device might be added into
the bus or probed which is triggered by deferred probe
just after completing of driver_attach() and before
'klist_add_tail(&priv->knode_bus, &bus->p->klist_drivers)',
so the device won't be probed by this driver.
This patch moves the below line
'klist_add_tail(&priv->knode_bus, &bus->p->klist_drivers)'
before driver_attach() inside bus_add_driver().
So fixes the problem since the below way can guarantee that
no probe(dev) may be lost.
CPU0 CPU1
driver_register
...
write(bus->driver_list)
smp_mb()
read(bus->device_list)
...
device_add
/* bus_add_device */
write(bus->device_list)
smp_mb()
/* bus_probe_device*/
read(bus->driver_list)
And the smp_mb() has been implicit by UNLOCK+LOCK
of 'klist' according to 'VARIETIES OF MEMORY BARRIER' part
of Documentation/memory-barriers.txt.
Reported-and-Tested-by: Russell King <[email protected]>
Cc: <[email protected]>
Signed-off-by: Ming Lei <[email protected]>
---
drivers/base/bus.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/base/bus.c b/drivers/base/bus.c
index 181ed26..3b5bddb 100644
--- a/drivers/base/bus.c
+++ b/drivers/base/bus.c
@@ -714,12 +714,12 @@ int bus_add_driver(struct device_driver *drv)
if (error)
goto out_unregister;
+ klist_add_tail(&priv->knode_bus, &bus->p->klist_drivers);
if (drv->bus->p->drivers_autoprobe) {
error = driver_attach(drv);
if (error)
goto out_unregister;
}
- klist_add_tail(&priv->knode_bus, &bus->p->klist_drivers);
module_add_driver(drv->owner, drv);
error = driver_create_file(drv, &driver_attr_uevent);
--
1.7.9.5
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