Messages in this thread | | | Date | Tue, 10 Mar 2009 10:19:47 -0400 (EDT) | From | Alan Stern <> | Subject | Re: [patch 01/11] Introducing generic hardware breakpoint handler interfaces |
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On Tue, 10 Mar 2009, Ingo Molnar wrote:
> * prasad@linux.vnet.ibm.com <prasad@linux.vnet.ibm.com> wrote: > > > > +static u8 tprio[HB_NUM]; /* Thread bp max priorities */ > > +LIST_HEAD(kernel_bps); /* Kernel breakpoint list */ > > +static LIST_HEAD(thread_list); /* thread_hw_breakpoint list */ > > +DEFINE_PER_CPU(struct cpu_hw_breakpoint, cpu_bp);
If nobody minds, I'll answer some of these questions on Prasad's behalf because they address parts of the code that were written before he took over the project.
> hm, why do we need the whole 'priority' mechanism? It seems very > over-designed to me.
This was done at Roland McGrath's express request. We should see what he has to say about it.
> The likelyhood of both user-space and kernel-space to use > hw-breakpoints is very low to begin with. And if they use them, > the likelyhood of there being more than 4 debugregs required in > the same context is even lower.
Not all architectures have 4 debug registers. Most have only one.
> If that happens we shouldnt try to be too smart about them - > just override user-space ones with kernel space ones and that's > it. No explicit priorities are needed.
Roland really did not want it done this way.
Alan Stern
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