20 Jul
2004
20 Jul
'04
11:14 p.m.
Lee Revell wrote:
There are still a few areas that need work, ioctl
gives me problems, but
the latest 2.6 kernels are quite good. If you look at the 'clean'
version of the voluntary kernel preemption patch it is pretty small. My
understanding is that the kernel is already preemptible anytime that a
spin lock (including the BKL) is not held, and that the voluntary kernel
preemption patch adds some scheduling points in places where it is safe
to sleep, but preemption is disabled because we are holding the BKL, and
that the number of these should approach zero as the kernel is improved
anyway.
That's confusing to me. It was my understanding that the BKL is used to
completely lock down the kernel so that no other CPU can have a process
get into the kernel... something like how SMP was done under 2.0.
So, if you sleep during a BKL, wouldn't that imply that nothing else
would be allowed to enter the kernel until after the kernel thread that
took the lock wakes up and releases the lock?