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Re: CVS commit: src/sys/compat/sa

On Mon, Oct 27, 2008 at 06:56:21PM +0100, Christoph Egger wrote:
> Bill Stouder-Studenmund wrote:
> > Module Name:        src
> > Committed By:       wrstuden
> > Date:               Mon Oct 27 16:52:04 UTC 2008
> > 
> > Modified Files:
> >     src/sys/compat/sa: compat_sa.c
> > 
> > Log Message:
> > Ok. Some calls to sa_upcall() pass in an 'l' that is not the current
> > lwp. Our "no-upcall" flagging however accesses l_pflag, and so we
> > can't access l->l_pflag. So access curlwp for the no-upcall-blocking
> > part.
> > 
> > 
> > To generate a diff of this commit:
> > cvs rdiff -r1.4 -r1.5 src/sys/compat/sa/compat_sa.c
> > 
> > Please note that diffs are not public domain; they are subject to the
> > copyright notices on the relevant files.
> If you want to be kernel preemptible safe, you must cache curlwp.


How could this use of curlwp change? I want the context that the code 
currently is running in. While I understand I could get preempted, won't I 
have to come back to the context I was in in order to resume?

If curlwp really can change in any of (well, just one of) the places that 
will call sa_upcall(), the correct answer is to disable preemption. The 
whole point of this change is to prevent BLOCKED upcalls from what we're 

Take care,


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