The following patch fixes a race condition in sg of sg_cmd_done racing
with sg_release. I've seen this bug hit several times on test machines
and the following patch fixes it. The race is that if srp->done is set
and the waiting thread gets a spurious wakeup immediately afterwards,
then the waiting thread can end up executing and completing, then getting
closed, freeing sfp before the wake_up_interruptible is called, which
then will result in an oops. The oops is fixed by locking around the
setting srp->done to 1 and the wake_up, and also locking around the
checking of srp->done, which guarantees that the wake_up_interruptible
will always occur before the sleeping thread gets a chance to run.
Signed-off-by: Brian King <brking@us.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>