Re: [patch 01/11] Introducing generic hardware breakpoint handlerinterfaces

From: Ingo Molnar
Date: Tue Mar 10 2009 - 09:51:20 EST



* prasad@xxxxxxxxxxxxxxxxxx <prasad@xxxxxxxxxxxxxxxxxx> 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);

hm, why do we need the whole 'priority' mechanism? It seems very
over-designed to me.

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.

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.

Ingo
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