Re: [PATCH 8/9] perf/breakpoint: Split breakpoint "check" and "commit"

Peter Zijlstra
2018-05-09T09:17:28Z

On Sun, May 06, 2018 at 09:19:54PM +0200, Frederic Weisbecker wrote:
> arch/arm/include/asm/hw_breakpoint.h | 5 ++++-
> arch/arm/kernel/hw_breakpoint.c | 22 +++-------------------
> arch/arm64/include/asm/hw_breakpoint.h | 5 ++++-
> arch/arm64/kernel/hw_breakpoint.c | 22 +++-------------------
> arch/powerpc/include/asm/hw_breakpoint.h | 5 ++++-
> arch/powerpc/kernel/hw_breakpoint.c | 22 +++-------------------
> arch/sh/include/asm/hw_breakpoint.h | 5 ++++-
> arch/sh/kernel/hw_breakpoint.c | 22 +++-------------------
> arch/x86/include/asm/hw_breakpoint.h | 5 ++++-
> arch/x86/kernel/hw_breakpoint.c | 23 +++--------------------
> arch/xtensa/include/asm/hw_breakpoint.h | 5 ++++-
> arch/xtensa/kernel/hw_breakpoint.c | 22 +++-------------------

Because of those ^,

> kernel/events/hw_breakpoint.c | 11 ++++++-----

would it not make sense to have a prelimenary patch doing something
like:

__weak int hw_breakpoint_arch_check(struct perf_event *bp)
{
return arch_validate_hwbkpt_settings(bp);
}

__weak void hw_breakpoint_arch_commit(struct perf_event *bp)
{
}

combined with this bit:

> diff --git a/kernel/events/hw_breakpoint.c b/kernel/events/hw_breakpoint.c
> index 6e28d28..6896ceeb 100644
> --- a/kernel/events/hw_breakpoint.c
> +++ b/kernel/events/hw_breakpoint.c
> @@ -402,11 +402,12 @@ int dbg_release_bp_slot(struct perf_event *bp)
>
> static int validate_hw_breakpoint(struct perf_event *bp)
> {
> - int ret;
> + int err;
>
> - ret = arch_validate_hwbkpt_settings(bp);
> - if (ret)
> - return ret;
> + err = hw_breakpoint_arch_check(bp, &bp->attr);
> + if (err)
> + return err;
> + hw_breakpoint_arch_commit(bp);
>
> if (arch_check_bp_in_kernelspace(bp)) {
> if (bp->attr.exclude_kernel)

And then convert the archs over one by one, and at the end remove the
weak thingies entirely?