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From:   Song Liu <songliubraving@fb.com>
To:     Jiri Olsa <jolsa@redhat.com>
CC:     Netdev <netdev@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "ast@kernel.org" <ast@kernel.org>,
        "daniel@iogearbox.net" <daniel@iogearbox.net>,
        Kernel Team <Kernel-team@fb.com>,
        "peterz@infradead.org" <peterz@infradead.org>,
        "acme@redhat.com" <acme@redhat.com>
Subject: Re: [PATCH 5/9] perf, bpf: save bpf_prog_info in a rbtree in perf_env
Thread-Topic: [PATCH 5/9] perf, bpf: save bpf_prog_info in a rbtree in
 perf_env
Thread-Index: AQHUwBU1jGfep/2GK02JoCQpTe8pjaXfQOUAgABM4YA=
Date:   Thu, 14 Feb 2019 17:01:48 +0000
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 <20190214122638.GD26714@krava>
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> On Feb 14, 2019, at 4:26 AM, Jiri Olsa <jolsa@redhat.com> wrote:
>=20
> On Fri, Feb 08, 2019 at 05:17:01PM -0800, Song Liu wrote:
>=20
> SNIP
>=20
>> diff --git a/tools/perf/util/env.h b/tools/perf/util/env.h
>> index d01b8355f4ca..5894a177b7cf 100644
>> --- a/tools/perf/util/env.h
>> +++ b/tools/perf/util/env.h
>> @@ -3,7 +3,10 @@
>> #define __PERF_ENV_H
>>=20
>> #include <linux/types.h>
>> +#include <linux/rbtree.h>
>> #include "cpumap.h"
>> +#include "rwsem.h"
>> +#include "bpf-event.h"
>>=20
>> struct cpu_topology_map {
>> 	int	socket_id;
>> @@ -64,6 +67,8 @@ struct perf_env {
>> 	struct memory_node	*memory_nodes;
>> 	unsigned long long	 memory_bsize;
>> 	u64                     clockid_res_ns;
>> +	struct rw_semaphore	bpf_info_lock;
>=20
> why's the lock needed?
>=20
> jirka

It protects the retries for bpf_prog_info and btf. For perf-top,=20
we will have one thread writing to the trees, while the main=20
thread reading from them.=20

Let me add comments to clarify.=20

Thanks,
Song