Date: Tue, 18 Aug 2015 11:41:34 -0700 From: Leonardo Fogel <leonardofogel@yahoo.com.br> To: freebsd-drivers@freebsd.org Subject: Race conditions Message-ID: <1439923294.98963.YahooMailBasic@web120801.mail.ne1.yahoo.com>
index | next in thread | raw e-mail
Hi.
The following code is an exerpt from the FreeBSD Architecture Handbook, chapter 11.1.1. Sample Driver Source. I've included labels i1, i2, i3.
int
mypci_open(struct cdev *dev, int oflags, int devtype, struct thread *td)
{
struct mypci_softc *sc;
/* Look up our softc. */
i1: sc = dev->si_drv1;
device_printf(sc->my_dev, "Opened successfully.\n");
return (0);
}
static int
mypci_attach(device_t dev)
{
struct mypci_softc *sc;
...
i2: sc->my_cdev = make_dev(&mypci_cdevsw, device_get_unit(dev),
UID_ROOT, GID_WHEEL, 0600, "mypci%u", device_get_unit(dev));
i3: sc->my_cdev->si_drv1 = sc;
printf("Mypci device loaded.\n");
return (0);
}
As I understand it, as soon as instruction at label i2 completes, there is a rare possibility that another thread opens the device file and executes the instruction at i1, before the instruction at i3 is executed. Is it correct? How could one fix it?
Thank you for your time.
Leonardo
help
Want to link to this message? Use this
URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?1439923294.98963.YahooMailBasic>