From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@elte.hu>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 01/15] perf_counter: unify and fix delayed counter wakeup
Date: Tue, 31 Mar 2009 08:37:05 +0200 [thread overview]
Message-ID: <1238481425.28248.1377.camel@twins> (raw)
In-Reply-To: <18897.44531.88862.844627@cargo.ozlabs.ibm.com>
On Tue, 2009-03-31 at 16:45 +1100, Paul Mackerras wrote:
> Peter Zijlstra writes:
>
> > +void perf_counter_wakeup(struct perf_counter *counter)
> > +{
> > + struct perf_mmap_data *data;
> > +
> > + rcu_read_lock();
> > + data = rcu_dereference(counter->data);
> > + if (data) {
> > + (void)atomic_xchg(&data->wakeup, POLL_IN);
>
> Really just a nit, but how is this atomic_xchg any different from
> atomic_set(&data->wakeup, POLL_IN) aside from being slower?
Probably, I got my head in a twist, atomic_set() is simply an unlocked
assignment (although volatile), and I read the value using a locked
xchg().
I wasn't sure how these two would interact and so I chickened out :-)
next prev parent reply other threads:[~2009-03-31 6:36 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-03-30 17:07 [PATCH 00/15] pending perf_counter bits Peter Zijlstra
2009-03-30 17:07 ` [PATCH 01/15] perf_counter: unify and fix delayed counter wakeup Peter Zijlstra
2009-03-31 5:45 ` Paul Mackerras
2009-03-31 6:37 ` Peter Zijlstra [this message]
2009-04-01 9:04 ` Ingo Molnar
2009-04-01 10:12 ` [tip:perfcounters/core] " Peter Zijlstra
2009-03-30 17:07 ` [PATCH 02/15] perf_counter: fix update_userpage() Peter Zijlstra
2009-04-01 10:12 ` [tip:perfcounters/core] " Peter Zijlstra
2009-03-30 17:07 ` [PATCH 03/15] perf_counter: kerneltop: simplify data_head read Peter Zijlstra
2009-04-01 10:13 ` [tip:perfcounters/core] " Peter Zijlstra
2009-03-30 17:07 ` [PATCH 04/15] perf_counter: executable mmap() information Peter Zijlstra
2009-04-01 10:13 ` [tip:perfcounters/core] " Peter Zijlstra
2009-03-30 17:07 ` [PATCH 05/15] perf_counter: kerneltop: parse the mmap data stream Peter Zijlstra
2009-04-01 10:13 ` [tip:perfcounters/core] " Peter Zijlstra
2009-03-30 17:07 ` [PATCH 06/15] perf_counter: powerpc: only reserve PMU hardware when we need it Peter Zijlstra
2009-04-01 10:13 ` [tip:perfcounters/core] " Paul Mackerras
2009-03-30 17:07 ` [PATCH 07/15] perf_counter: make it possible for hw_perf_counter_init to return error codes Peter Zijlstra
2009-04-01 10:13 ` [tip:perfcounters/core] " Paul Mackerras
2009-03-30 17:07 ` [PATCH 08/15] perf_counter: x86: proper error propagation for the x86 hw_perf_counter_init() Peter Zijlstra
2009-04-01 10:13 ` [tip:perfcounters/core] " Peter Zijlstra
2009-03-30 17:07 ` [PATCH 09/15] perf_counter tools: optionally scale counter values in perfstat mode Peter Zijlstra
2009-04-01 9:39 ` Ingo Molnar
2009-04-01 10:50 ` Paul Mackerras
2009-04-01 10:14 ` [tip:perfcounters/core] " Paul Mackerras
2009-03-30 17:07 ` [PATCH 10/15] perf_counter: small cleanup of the output routines Peter Zijlstra
2009-04-01 10:14 ` [tip:perfcounters/core] " Peter Zijlstra
2009-03-30 17:07 ` [PATCH 11/15] perf_counter: re-arrange the perf_event_type Peter Zijlstra
2009-04-01 10:14 ` [tip:perfcounters/core] " Peter Zijlstra
2009-03-30 17:07 ` [PATCH 12/15] pref_counter: kerneltop: update event_types Peter Zijlstra
2009-04-01 10:14 ` [tip:perfcounters/core] perf_counter tools: " Peter Zijlstra
2009-03-30 17:07 ` [PATCH 13/15] perf_counter: provide generic callchain bits Peter Zijlstra
2009-03-31 6:12 ` Paul Mackerras
2009-03-31 6:39 ` Peter Zijlstra
2009-03-31 7:24 ` Corey Ashford
2009-03-31 8:43 ` Peter Zijlstra
2009-03-31 9:09 ` Paul Mackerras
2009-03-31 9:12 ` Paul Mackerras
2009-03-31 14:00 ` Peter Zijlstra
2009-03-31 17:11 ` Corey Ashford
2009-04-01 3:48 ` Paul Mackerras
2009-04-01 7:59 ` Peter Zijlstra
2009-04-01 8:45 ` Paul Mackerras
2009-04-01 10:00 ` Ingo Molnar
2009-04-01 11:53 ` Paul Mackerras
2009-04-01 23:25 ` Corey Ashford
2009-04-02 6:43 ` Peter Zijlstra
2009-04-02 7:41 ` Peter Zijlstra
2009-04-02 9:10 ` Paul Mackerras
2009-04-02 9:14 ` Peter Zijlstra
2009-04-01 10:14 ` [tip:perfcounters/core] " Peter Zijlstra
2009-03-30 17:07 ` [PATCH 14/15] perf_counter: x86: callchain support Peter Zijlstra
2009-04-01 10:14 ` [tip:perfcounters/core] " Peter Zijlstra
2009-03-30 17:07 ` [PATCH 15/15] perf_counter: pmc arbitration Peter Zijlstra
2009-04-01 10:15 ` [tip:perfcounters/core] " Peter Zijlstra
2009-03-31 5:43 ` [PATCH 00/15] pending perf_counter bits Paul Mackerras
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