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Am Dienstag, 19. Dezember 2006 23:33 schrieb J: > Thank you for the response. > > > This code depends on protection from BKL. > > Really? I cannot find many lock_kernel calls in > USB directory and those, which I can find, > don't appear to protect usb_serial_disconnect > and serial_close from being called at the same time. serial_close is safe because serial_disconnect lowers the refcount by one. usb_serial_probe() and usb_serial_open() both increment the refcount; the former implicitly. > May be the protection is at a higher level? > Personally I don't beleive it. > If you know how this thing is supposed to work, > please, tell me. The data structure to protect is serial_table. Everything else is protected by refcounts. Therefore the interesting race is between open and disconnect. Open is called with BKL (fs/char_dev.c::chrdev_open) Now, regarding disconnect. It used to be called with BKL held. I haven't been able to verify that this is still the case. If not, then there's a race. In addition usb_serial_probe() uses get_free_serial() early in the process before the device is ready. Without BKL, this too, races with open. People, do we take BKL in khubd? Regards Oliver - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | ||||||||||
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