From: Peter Zijlstra <peterz@infradead.org>
To: Jiri Olsa <jolsa@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>,
linux-kernel@vger.kernel.org, Andi Kleen <andi@firstfloor.org>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Corey Ashford <cjashfor@linux.vnet.ibm.com>,
David Ahern <dsahern@gmail.com>,
Frederic Weisbecker <fweisbec@gmail.com>,
Ingo Molnar <mingo@kernel.org>,
"Jen-Cheng(Tommy) Huang" <tommy24@gatech.edu>,
Namhyung Kim <namhyung@kernel.org>,
Paul Mackerras <paulus@samba.org>,
Stephane Eranian <eranian@google.com>
Subject: Re: [PATCH 1/9] perf: Remove redundant parent context check from context_equiv
Date: Mon, 8 Sep 2014 15:20:54 +0200 [thread overview]
Message-ID: <20140908132054.GF6758@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20140908121952.GB17728@krava.brq.redhat.com>
[-- Attachment #1: Type: text/plain, Size: 2109 bytes --]
On Mon, Sep 08, 2014 at 02:19:52PM +0200, Jiri Olsa wrote:
> > I have another 'problem' with 179033b3e064. What if you 'want' to
> > continue monitoring after the initial task died? Eg. if you want to
> > monitor crap that unconditionally daemonizes.
>
> right.. did not think of that.. need to check more, but
> seems like just the check for children should be enough
>
Indeed, that should work.
> ---
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index bf482ccbdbe1..341d0b47ca14 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -3568,6 +3568,19 @@ static int perf_event_read_one(struct perf_event *event,
> return n * sizeof(u64);
> }
>
> +static bool is_event_hup(struct perf_event *event)
> +{
> + bool no_children;
> +
> + if (event->state != PERF_EVENT_STATE_EXIT)
> + return false;
> +
> + mutex_lock(&event->child_mutex);
> + no_children = list_empty(&event->child_list);
> + mutex_unlock(&event->child_mutex);
> + return no_children;
> +}
> +
> /*
> * Read the performance event - simple non blocking version for now
> */
> @@ -3582,8 +3595,7 @@ perf_read_hw(struct perf_event *event, char __user *buf, size_t count)
> * error state (i.e. because it was pinned but it couldn't be
> * scheduled on to the CPU at some point).
> */
> - if ((event->state == PERF_EVENT_STATE_ERROR) ||
> - (event->state == PERF_EVENT_STATE_EXIT))
> + if ((event->state == PERF_EVENT_STATE_ERROR) || (is_event_hup(event)))
> return 0;
Do we want this? It seems like a fairly sensible thing to start a
counter and wait for the thing to die, only to then read the total
count. But with this on we get 0s.
I suppose Stephane's email got to you after you did this and we should
be dropping this thing entirely?
> if (count < event->read_size)
> @@ -3614,7 +3626,7 @@ static unsigned int perf_poll(struct file *file, poll_table *wait)
>
> poll_wait(file, &event->waitq, wait);
>
> - if (event->state == PERF_EVENT_STATE_EXIT)
> + if (is_event_hup(event))
> return events;
>
> /*
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next prev parent reply other threads:[~2014-09-08 13:21 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-08-25 14:45 [RFCv2 0/9] perf: Allow leader sampling on inherited events Jiri Olsa
2014-08-25 14:45 ` [PATCH 1/9] perf: Remove redundant parent context check from context_equiv Jiri Olsa
2014-09-02 10:50 ` Peter Zijlstra
2014-09-08 9:43 ` Jiri Olsa
2014-09-08 9:45 ` Peter Zijlstra
2014-09-08 9:48 ` Peter Zijlstra
2014-09-08 10:01 ` Peter Zijlstra
2014-09-08 11:39 ` Peter Zijlstra
2014-09-08 12:19 ` Jiri Olsa
2014-09-08 13:20 ` Peter Zijlstra [this message]
2014-09-08 12:32 ` Jiri Olsa
2014-09-08 12:01 ` Jiri Olsa
2014-09-08 13:34 ` Peter Zijlstra
2014-09-08 15:13 ` Peter Zijlstra
2014-09-08 16:45 ` Jiri Olsa
2014-09-09 10:20 ` Peter Zijlstra
2014-09-10 13:57 ` Peter Zijlstra
2014-09-10 14:35 ` Jiri Olsa
2014-09-24 14:58 ` [tip:perf/core] Revert "perf: Do not allow optimized switch for non-cloned events" tip-bot for Jiri Olsa
2014-08-25 14:45 ` [PATCH 2/9] perf: Deny optimized switch for events read by PERF_SAMPLE_READ Jiri Olsa
2014-09-02 10:52 ` Peter Zijlstra
2014-09-08 10:00 ` Jiri Olsa
2014-09-08 10:11 ` Peter Zijlstra
2014-09-08 16:39 ` Jiri Olsa
2014-08-25 14:45 ` [PATCH 3/9] perf: Allow PERF_FORMAT_GROUP format on inherited events Jiri Olsa
2014-08-25 14:45 ` [PATCH 4/9] perf tools: Add support to traverse xyarrays Jiri Olsa
2014-08-25 14:45 ` [PATCH 5/9] perf tools: Add pr_warning_once debug macro Jiri Olsa
2014-08-25 14:45 ` [PATCH 6/9] perf tools: Add hash of periods for struct perf_sample_id Jiri Olsa
2014-08-25 14:45 ` [PATCH 7/9] perf tools: Allow PERF_FORMAT_GROUP for inherited events Jiri Olsa
2014-08-25 14:45 ` [PATCH 8/9] perf script: Add period data column Jiri Olsa
2014-08-27 14:33 ` David Ahern
2014-10-17 16:10 ` Jiri Olsa
2014-10-17 18:22 ` Arnaldo Carvalho de Melo
2014-10-18 7:07 ` [tip:perf/urgent] " tip-bot for Jiri Olsa
2014-08-25 14:45 ` [PATCH 9/9] perf script: Add period as a default output column Jiri Olsa
2014-08-27 14:40 ` David Ahern
2014-10-17 16:11 ` Jiri Olsa
2014-10-18 7:07 ` [tip:perf/urgent] " tip-bot for Jiri Olsa
2014-08-25 14:51 ` [RFCv2 0/9] perf: Allow leader sampling on inherited events Jiri Olsa
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