Kernel

在-CURRENT上发表那个patch之后果然有很多热心人帮助测试。有人说在X里面接USB键盘会花，现在还在找原因……

I have enabled PREEMPTION, FULL_PREEMPTION with ULE. Now I get strange result here:

• propagate_priority gets a TD_ON_LOCK(td)
• It tries to panic(), unfortunatelly, ts->ts_lockobj here is NULL
• A fatal trap 12 happens.

It seems that ts->ts_lockobj was touched by sched_lend_prio, for unknown reasons. Maybe there is some lock releases?

调试能力明显下降了，本来早就应该想到的，结果整整花了一个钟头才找到故障点，老了，明明看到堆栈毁了的居然还去相信调试器：（

Finally I caught the kernel panic caused by some strange bugs found in thread scheduling. Investigating the crashdump.

The following change is considered as a new errata candadite from my view:

peter 2005-04-18 21:36:17 UTC FreeBSD src repository

Modified files: (Branch: RELENG_5_4)
sys/i386/i386 genassym.c vm86bios.s
sys/i386/include pcb.h
Log:
MFC: stop i386_vm86() from either panicing or trashing random pages.

This can improve stability, however we can not easily prove that it is producable :-) So I have turned that to re@.

To quote him:

So I finally tried DragonFly on one of our test servers (not my desktop :-). It seems that DragonFly still have some issues with the SATA devices. I am trying to fix it, maybe by porting some good FreeBSD ATAng code.

DragonFly has gave us some good examples that how a user-friendly operating system should, and some different way on designing a MP-capable architecture. Thanks, Matt!

1. We should not caclucate the superblock summary, since it can at most lag 30 seconds’ change, and doing the caclucate is painful delay. What we should do is to transfer the responsibility to background fsck
2. newfs(8) should warn about the snapshot is actually unable to create, in case fssize is greater than maxfilesize.

The patch for 1) is available at http://people.freebsd.org/~delphij/ffs/patch-sbsummary. I will work on 2) shortly, as it’s quite simpler than 1).

A post on tech-kern has suggested that NetBSD has better performance on several aspects. I think FreeBSD should take some of their ideas. What’s more, I believe it’s more important to have something that is unique in FreeBSD, not doing what’s the equivalent because “Solaris have this” :-)

Yes I want to install FreeBSD on my Windows partition :-)