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>
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Hi.
The following code is an exerpt from the FreeBSD Architecture Handbook, cha=
pter 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 =3D 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 =3D 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 =3D 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 t=
he instruction at i1, before the instruction at i3 is executed. Is it corre=
ct? How could one fix it?
Thank you for your time.
Leonardo
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