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Wed, 12 Feb 2020 15:28:43 -0800 (PST) Received: from localhost ([2620:15c:6:12:9c46:e0da:efbf:69cc]) by smtp.gmail.com with ESMTPSA id t7sm240428qkm.136.2020.02.12.15.28.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 12 Feb 2020 15:28:30 -0800 (PST) Date: Wed, 12 Feb 2020 18:28:30 -0500 From: Joel Fernandes To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, rostedt@goodmis.org, mingo@kernel.org, gregkh@linuxfoundation.org, gustavo@embeddedor.com, tglx@linutronix.de, paulmck@kernel.org, josh@joshtriplett.org, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com, "Steven Rostedt (VMware)" Subject: Re: [PATCH v2 6/9] perf,tracing: Prepare the perf-trace interface for RCU changes Message-ID: <20200212232830.GB170680@google.com> References: <20200212210139.382424693@infradead.org> <20200212210750.142334759@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200212210750.142334759@infradead.org> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 12, 2020 at 10:01:45PM +0100, Peter Zijlstra wrote: > The tracepoint interface will stop providing regular RCU context; make > sure we do it ourselves, since perf makes use of regular RCU protected > data. > > Suggested-by: Steven Rostedt (VMware) > Suggested-by: Mathieu Desnoyers > Signed-off-by: Peter Zijlstra (Intel) > --- > kernel/events/core.c | 5 +++++ > 1 file changed, 5 insertions(+) > > --- a/kernel/events/core.c > +++ b/kernel/events/core.c > @@ -8950,6 +8950,7 @@ void perf_tp_event(u16 event_type, u64 c > { > struct perf_sample_data data; > struct perf_event *event; > + unsigned long rcu_flags; The flags are not needed I guess, if you agree on not using in_nmi() in trace_rcu_enter(). thanks, - Joel > struct perf_raw_record raw = { > .frag = { > @@ -8961,6 +8962,8 @@ void perf_tp_event(u16 event_type, u64 c > perf_sample_data_init(&data, 0, 0); > data.raw = &raw; > > + rcu_flags = trace_rcu_enter(); > + > perf_trace_buf_update(record, event_type); > > hlist_for_each_entry_rcu(event, head, hlist_entry) { > @@ -8996,6 +8999,8 @@ void perf_tp_event(u16 event_type, u64 c > } > > perf_swevent_put_recursion_context(rctx); > + > + trace_rcu_exit(rcu_flags); > } > EXPORT_SYMBOL_GPL(perf_tp_event); > > >