On Thursday, September 2, 2021 11:32:07 AM CEST Greg Kroah-Hartman wrote: > On Sat, Aug 28, 2021 at 01:36:56PM +0200, Fabio M. De Francesco wrote: > > Remove _enter_critical_mutex() and _exit_critical_mutex(). They are > > unnecessary wrappers, respectively to mutex_lock_interruptible() and > > to mutex_unlock(). They also have an odd interface that takes an unused > > argument named pirqL of type unsigned long. > > The original code enters the critical section if the mutex API is > > interrupted while waiting to acquire the lock; therefore it could lead > > to a race condition. Use mutex_lock() because it is uninterruptible and > > so avoid that above-mentioned potential race condition. > > > > Tested-by: Pavel Skripkin <paskripkin@xxxxxxxxx> > > Reviewed-by: Pavel Skripkin <paskripkin@xxxxxxxxx> > > Signed-off-by: Fabio M. De Francesco <fmdefrancesco@xxxxxxxxx> > > --- > > > > v5: Fix a typo in the subject line. Reported by Aakash Hemadri. > > > > v4: Tested and reviewed by Pavel Skripkin. No changes to the code. > > > > v3: Assume that the original authors don't expect that > > mutex_lock_interruptible() can be really interrupted and then lead to > > a potential race condition. Furthermore, Greg Kroah-Hartman makes me > > notice that "[] one almost never needs interruptible locks in a driver". > > Therefore, replace the calls to mutex_lock_interruptible() with calls to > > mutex_lock() since the latter is uninterruptible and avoid race > > conditions without the necessity to handle -EINTR errors. > > Based on a recent conversation on the linux-usb mailing list, perhaps I > was wrong: > https://lore.kernel.org/r/ 20210829015825.GA297712@xxxxxxxxxxxxxxxxxxx > > Can you check what happens with your change when you disconnect the > device and these code paths are being called? That is when you do want > the lock interrupted. > > Yes, the logic still seems wrong, but I don't want to see the code now > just lock up entirely with this change as it is a change in how things > work from today. > > thanks, > > greg k-h Hi Greg, I guess you've already read the responses from Pavel: He tested the code, again and again, and it works properly (connect/disconnect, "ip link show", and so on). Furthermore, this patch already has his "Tested-by:" and "Reviewed-by:" tags. Pavel and I agree on the fact that this patch can be applied as-is, however we obviously know that it's only up to you. In the meantime he found and fixed a bad design issue that was revealed by using my patch. Please, let me know if there is anything else I can do. Thanks, Fabio
