From: Oleg Nesterov <oleg@redhat.com>
To: Jiri Olsa <jolsa@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>,
Milind Chabbi <chabbi.milind@gmail.com>,
lkml <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@kernel.org>,
Namhyung Kim <namhyung@kernel.org>,
David Ahern <dsahern@gmail.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Frederic Weisbecker <frederic@kernel.org>
Subject: Re: [PATCH 2/2] perf/hw_breakpoint: Modify breakpoint even if the new attr has disabled set
Date: Mon, 6 Aug 2018 14:48:40 +0200 [thread overview]
Message-ID: <20180806124839.GC7840@redhat.com> (raw)
In-Reply-To: <20180806101241.6444-3-jolsa@kernel.org>
On 08/06, Jiri Olsa wrote:
>
> We need to change the breakpoint even if the attr with
> new fields has disabled set to true.
Agreed... The patch looks fine to me, but I have a question
> int modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *attr)
> {
> + int err;
> +
> /*
> * modify_user_hw_breakpoint can be invoked with IRQs disabled and hence it
> * will not be possible to raise IPIs that invoke __perf_event_disable.
> @@ -520,11 +522,11 @@ int modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *att
> else
> perf_event_disable(bp);
>
> - if (!attr->disabled) {
> - int err = modify_user_hw_breakpoint_check(bp, attr, false);
> + err = modify_user_hw_breakpoint_check(bp, attr, false);
> + if (err)
> + return err;
>
> - if (err)
> - return err;
> + if (!attr->disabled) {
> perf_event_enable(bp);
> bp->attr.disabled = 0;
Afaics you do not need to clear attr.disabled, modify_user_hw_breakpoint_check()
updates it if err = 0. So I think
if (!bp->attr.disabled)
perf_event_enable(bp);
will look a bit better.
But, with or without this fix, shouldn't we set .disabled = 1 if modify_() fails?
IIUC this doesn't matter, bp->attr.disabled is not really used anyway, but looks a
bit confusing.
Oleg.
next prev parent reply other threads:[~2018-08-06 12:48 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-06 10:12 [PATCH 0/2] perf/hw_breakpoint: Fix breakpoint modify Jiri Olsa
2018-08-06 10:12 ` [PATCH 1/2] perf tests: Add breakpoint modify test Jiri Olsa
2018-08-06 10:12 ` [PATCH 2/2] perf/hw_breakpoint: Modify breakpoint even if the new attr has disabled set Jiri Olsa
2018-08-06 12:48 ` Oleg Nesterov [this message]
2018-08-06 13:07 ` Oleg Nesterov
2018-08-06 13:37 ` Jiri Olsa
2018-08-06 13:49 ` Oleg Nesterov
2018-08-06 14:21 ` Jiri Olsa
2018-08-06 13:23 ` Jiri Olsa
2018-08-06 13:46 ` Oleg Nesterov
2018-08-06 15:08 ` [PATCH 3/2] perf/hw_breakpoint: Remove superfluous bp->attr.disabled = 0 " Jiri Olsa
2018-08-06 16:34 ` Oleg Nesterov
2018-08-07 8:16 ` Jiri Olsa
2018-08-07 9:10 ` Oleg Nesterov
2018-08-07 14:39 ` Jiri Olsa
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