yongari at kt-is.co.kr
Wed Sep 22 01:36:49 PDT 2004
On Mon, Sep 20, 2004 at 07:40:06PM +0900, To dhaigh at gatorzone.com wrote:
> On Fri, Sep 17, 2004 at 09:29:41AM -0400, Doug Haigh wrote:
> > I am not sure if the PR got updated, but I wanted to let you know that the
> > printf in a kernel thread only fails if you are on a SMP machine. It appears
> > that if you printf on a CPU other than CPU #0, it will panic the kernel.
> After reading your mail, I made a small test program which creates
> a kernel thread and ran it on AXe(UP) and U2(SMP).
> Under AXe it worked as expected but it paniced on U2.
> So it seems that there is some issues in OF console.
> Backtrace for the panic is somthing like:
While looking into the ofw_console(4) code I noticed there is
possible races there. So I patched the code and ran it. However
it didn't fix the problem. Since we can't simply use a mutex in
ofw_cons_putc(), there should be other way to workaround this.
Have no idea yet.
If you really really want to see your messages from a kernel
thread you can do one of the following(tested on U2):
1. remove invocation of timeout(9) in ofw_console.c. With this
modification, you can't enter characters with keyboard.
2. use sc + creator + uart + puc instead of ofw_console(4)
On my U2, keyboard input didn't work.
If you want to see my partial patch as a starting point please let
Pyun YongHyeon <http://www.kr.freebsd.org/~yongari>
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