Kernel

最近一直在抽空琢磨一些相关的问题。响应时间？抢占？等等。

Available here.

AT YOUR OWN RISK!!

Now I got (partially) the point:

• A newly fork’ed thread grabs Giant
• Subsequently, the mutex procedure will call turnstile_wait
• However, the td->td_sched->ke_runq is NULL (means that some part of the new thread is not initialized completely)
• So boom! panic.

Interestingly this does not happen in !PREEMPTION case.

Now my question are:

1. who forks?
2. is it the child? the parent?
3. why the initialization is not completed with a wrong result?

I have done several experiments/asserts to ensure that the panic is related to ULE+PREEMPTION case only.

ULE: no panic
4BSD: no panic
4BSD+PREEMPTION: no panic

My latest progress is that I found that sched_switch in ULE for the threaded case, can decide whether subsequent call would panic. Investigating.

My company has offered me some test equipment (namely, a HP 360 with ILO, which is *great* for debugging at home!), and I has started to trip over the ULE code and find for bugs.

It seems that I have hit a bug, where kseq_nice_rem is being called too much. Have read the code and added some KASSERT/MPASS’es.

Today quakelee@ has reported that an(4) is broken with a recent -CURRENT. I have identified that that was related to our recent ifnet change and has fixed it under scottl@’s approval.

We are only 1 day to the great 6.0-STABLE code freeze, which will result in 7.0-CURRENT, 6.0-STABLE, and finally, 6.0-RELEASE!

Deploy FreeBSD on your spare boxes, g/f’s laptops, etc., to help us toward an excellent release!

Now they are at r6. I hope that FreeBSD will have dabian base for their 3.x series soon, which will provide better compatibility and ease the way of users to migrate to FreeBSD.

So he has finally (after about six or more months) imported read-only ResierFS, congratulations, dumbbell, you have made a quite impressive change!

Since 6-ism VFS interface is quite different from 5-ism, so this change is not likely to be merged IMO. Read-write is also not likely to be available soon, but anyway, ReiserFS is a nice FS and supporting it is a good move.

Today another GPL kernel has problem with a 4TB RAID5 array, it thought that it is 2.1TB (on boot) and refuse to initialize it with its native file systems, including ReiserFS. On contrary, FreeBSD 5.4 and 6.0 works smoothly with a GENERIC kernel. Oh well…