RE: [PATCH] NFC: Driver for Inside Secure MicroRead NFC chip

From: Waldemar.Rymarkiewicz
Date: Thu Mar 17 2011 - 09:38:22 EST


>An application can open the device, and then do a
>pthread_create() or a fork(). In either case, you have two
>concurrent threads that have access to the file pointer and
>can read from it concurrently, which is inherently racy
>regarding which of the processes gets the data.

In that case I would relay on the application to synchronise the access.

>This is not very different from opening the file descriptor in
>multiple processes, which you prevent using your logic.

but in the case when two independent applications try to open my device I can't let the second to access. They obviously won't synch the access.

>You can of course argue that you try your best to prevent the
>race. Traditionally, e.g. on serial ports and the like, we
>don't do this but instead rely on user space synchronizing the
>access. What you have to make sure of course is that multiple
>threads calling read on the same file can never bring the
>kernel driver into an invalid state.

I assume, if an application shares the file pointer deliberately it have to sync the access. In other cases, the driver needs to secure it.

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at