Arnd, >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. Waldek-- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
