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SubjectRe: [PATCH 3/2] perf/hw_breakpoint: Remove superfluous bp->attr.disabled = 0 new attr has disabled set
On 08/06, Jiri Olsa wrote:
>
> Once the breakpoint was succesfully modified, the attr->disabled
> value is in bp->attr.disabled. So there's no reason to set it
> again, removing that.
>
> Link: http://lkml.kernel.org/n/tip-v5oaellzsmyszv3rfucuxkp0@git.kernel.org
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> ---
> kernel/events/hw_breakpoint.c | 5 ++---
> 1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/events/hw_breakpoint.c b/kernel/events/hw_breakpoint.c
> index fb229d9c7f3c..3e560d7609fd 100644
> --- a/kernel/events/hw_breakpoint.c
> +++ b/kernel/events/hw_breakpoint.c
> @@ -526,10 +526,9 @@ int modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *att
> if (err)
> return err;
>
> - if (!attr->disabled) {
> + if (!attr->disabled)
> perf_event_enable(bp);
> - bp->attr.disabled = 0;
> - }
> +

Yes, but again, this still looks confusing.

IMO, we should either remove "bp->attr.disabled = attr->disabled" in
modify_user_hw_breakpoint_check() because bp->attr.disabled is not really
used, or we should set bp->attr.disabled = 1 on failure just for consistency.


Hmm... actually ptrace_get_dr7() checks ->attr.disabled, so we can hit
WARN_ON(second_pass) in ptrace_write_dr7() in case when attr.disabled is
falsely 0 because modify_user_hw_breakpoint_check() failed before?

It seems I am totally confused and need to sleep ;)

Oleg.

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