Messages in this thread | | | Date | Tue, 19 May 2015 12:51:21 +0200 | From | Peter Zijlstra <> | Subject | Re: [patch 3/6] x86, perf, cqm: Remove pointless spinlock from state cache |
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On Tue, May 19, 2015 at 10:13:18AM +0100, Matt Fleming wrote: > On Tue, 19 May, at 12:00:53AM, Thomas Gleixner wrote: > > struct intel_cqm_state is a strict per cpu cache of the rmid and the > > usage counter. It can never be modified from a remote cpu. > > > > The 3 functions which modify the content: start, stop and del (del > > maps to stop) are called from the perf core with interrupts disabled > > which is enough protection for the per cpu state values. > > > > Signed-off-by: Thomas Gleixner <tglx@linutronix.de> > > --- > > arch/x86/kernel/cpu/perf_event_intel_cqm.c | 17 ++++++----------- > > 1 file changed, 6 insertions(+), 11 deletions(-) > > The state locking code was taken from Peter's original patch last year, > so it would be good for him to chime in that this is safe. It's probably > just that it was necessary in Peter's patches but after I refactored > bits I forgot to rip it out. > > But yeah, from reading the code again the lock does look entirely > superfluous.
I think that all stems from a point in time when it wasn't at all clear to me what the hardware looked like, but what do I know, I can't even remember last week.
All the patches looked good to me, so I already queued them.
I'll add your Ack on them.
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