21.07.2015 17:22, Oliver Neukum пишет:
On Mon, 2015-07-20 at 21:13 +0300, Eugene Shatokhin wrote:And here, the code clears EVENT_RX_KILL bit in dev->flags, which may execute concurrently with the above operation: #0 clear_bit (bitops.h:113, inlined) #1 usbnet_bh (usbnet.c:1475) /* restart RX again after disabling due to high error rate */ clear_bit(EVENT_RX_KILL, &dev->flags); If clear_bit() is atomic w.r.t. setting dev->flags to 0, this race is not a problem, I guess. Otherwise, it may be.clear_bit is atomic with respect to other atomic operations. So how about this: Regards Oliver
Thanks for the quick replies! My comments are below.
From 1c4e685b3a9c183e04c46b661830e5c7ed35b513 Mon Sep 17 00:00:00 2001From: Oliver Neukum <oneukum@xxxxxxxx> Date: Tue, 21 Jul 2015 16:19:40 +0200 Subject: [PATCH] usbnet: fix race between usbnet_stop() and the BH Does this do the job? Signed-off-by: Oliver Neukum <oneukum@xxxxxxxx> --- drivers/net/usb/usbnet.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c index 3c86b10..77a9a86 100644 --- a/drivers/net/usb/usbnet.c +++ b/drivers/net/usb/usbnet.c @@ -778,7 +778,7 @@ int usbnet_stop (struct net_device *net) { struct usbnet *dev = netdev_priv(net); struct driver_info *info = dev->driver_info; - int retval, pm; + int retval, pm, mpn; clear_bit(EVENT_DEV_OPEN, &dev->flags); netif_stop_queue (net); @@ -813,14 +813,17 @@ int usbnet_stop (struct net_device *net) * can't flush_scheduled_work() until we drop rtnl (later), * else workers could deadlock; so make workers a NOP. */
+ mpn = !test_and_clear_bit(EVENT_NO_RUNTIME_PM, &dev->flags);
Right, I missed that. Indeed, if one needs EVENT_NO_RUNTIME_PM bit, one should get it before dev->flags is set to 0.
dev->flags = 0;
I suppose usbnet_bh() cannot be re-scheduled at this point. And if it is running now, tasklet_kill will wait till it finishes. So, I guess, it would be enough to zero dev->flags after "tasklet_kill (&dev->bh);" rather than before it, like it is now.
Anyway, if it is needed to clear any particular flags to prevent re-scheduling of usbnet_bh(), this can be done here with clear_bit(). Not sure if there are such flags, I am by no means an expert in usbnet.
del_timer_sync (&dev->delay); tasklet_kill (&dev->bh);
The following part is not necessary, I think. usbnet_bh() does not touch EVENT_NO_RUNTIME_PM bit explicitly and these bit operations are atomic w.r.t. each other.
+ mpn |= !test_and_clear_bit(EVENT_NO_RUNTIME_PM, &dev->flags); + /* in case the bh reset a flag */
But zeroing dev->flags here is necessary, I agree.
+ dev->flags = 0;
if (!pm) usb_autopm_put_interface(dev->intf); - if (info->manage_power && - !test_and_clear_bit(EVENT_NO_RUNTIME_PM, &dev->flags)) + if (info->manage_power && mpn) info->manage_power(dev, 0); else usb_autopm_put_interface(dev->intf);
Regards, Eugene -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
