linux-kernel - Re: [PATCH] perf/core: fast breakpoint modification via _IOC_MODIFY

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Message-ID: <20171106092305.GA16382@krava>
Date:   Mon, 6 Nov 2017 10:23:05 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Milind Chabbi <chabbi.milind@...il.com>
Cc:     peterz@...radead.org, mingo@...hat.com, acme@...nel.org,
        alexander.shishkin@...ux.intel.com, namhyung@...nel.org,
        linux-kernel@...r.kernel.org, mtk.manpages@...il.com,
        linux-man@...r.kernel.org, mpe@...erman.id.au, ak@...ux.intel.com,
        kan.liang@...el.com, hbathini@...ux.vnet.ibm.com,
        sukadev@...ux.vnet.ibm.com, yao.jin@...ux.intel.com
Subject: Re: [PATCH] perf/core: fast breakpoint modification via
 _IOC_MODIFY_BREAKPOINT

On Sun, Nov 05, 2017 at 02:35:34PM -0800, Milind Chabbi wrote:

SNIP

> +static int _perf_event_modify_breakpoint(struct perf_event *bp,
> + struct perf_event_attr *attr)
> +{
> + u64 old_addr = bp->attr.bp_addr;
> + u64 old_len = bp->attr.bp_len;
> + int old_type = bp->attr.bp_type;
> + int err = 0;
> +
> + _perf_event_disable(bp);
> +
> + bp->attr.bp_addr = attr->bp_addr;
> + bp->attr.bp_type = attr->bp_type;
> + bp->attr.bp_len = attr->bp_len;
> +
> + if (attr->disabled)
> + goto end;
> +
> + err = validate_hw_breakpoint(bp);

thre patch is mangled.. seems like you've lost all your tabs somehow

anyway, should you also do the release_bp_slot/reserve_bp_slot
magic to keep the slot accounting corrent?

jirka