linux-kernel - Re: [PATCHv3 0/5] perf/hw_breakpoint: Fix breakpoint modify

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Date:   Fri, 17 Aug 2018 13:48:58 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        David Ahern <dsahern@...il.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Milind Chabbi <chabbi.milind@...il.com>,
        Oleg Nesterov <oleg@...hat.com>,
        Frederic Weisbecker <frederic@...nel.org>
Subject: Re: [PATCHv3 0/5] perf/hw_breakpoint: Fix breakpoint modify

On Fri, Aug 10, 2018 at 12:47:25PM +0200, Jiri Olsa wrote:
> hi,
> Milind reported that modify_user_hw_breakpoint wouldn't
> allow the breakpoint changing if the new attr had 'disabled'
> set to true.
> 
> I found a case where it actualy prevents ptrace user interface
> to change the breakpoint. It's described in patch 1 as perf test,
> patch 2 is the breakpoint code fix.
> 
> I ran strace tests, nothing (new) broken there..
> 
> v3 changes:
>   - added Oleg's ack for patch 3
>   - new patches 4,5 based on Oleg's suggestions
>     replacing the v2 fallback approach by enabling
>     the event directly after failed modification

Ingo, Arnaldo,
would you please pick up those, or should I pushed them through somebody else?

thanks,
jirka

> 
> v2 changes:
>   - added Oleg's ack for patch 2
>   - added new changes based on Oleg's questions
>     plus new test code
> 
> thanks,
> jirka
> 
> ---
> Jiri Olsa (5):
>       perf tests: Add breakpoint modify tests
>       perf/hw_breakpoint: Modify breakpoint even if the new attr has disabled set
>       perf/hw_breakpoint: Remove superfluous bp->attr.disabled = 0
>       perf/hw_breakpoint: Enable breakpoint in modify_user_hw_breakpoint
>       perf/hw_breakpoint: Simplify breakpoint enable in perf_event_modify_breakpoint
> 
>  kernel/events/core.c                     |  11 ++-----
>  kernel/events/hw_breakpoint.c            |  13 ++++----
>  tools/perf/arch/x86/include/arch-tests.h |   1 +
>  tools/perf/arch/x86/tests/Build          |   1 +
>  tools/perf/arch/x86/tests/arch-tests.c   |   6 ++++
>  tools/perf/arch/x86/tests/bp-modify.c    | 213 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  6 files changed, 230 insertions(+), 15 deletions(-)
>  create mode 100644 tools/perf/arch/x86/tests/bp-modify.c