netdev - Re: [PATCH 5/9] perf, bpf: save bpf_prog_info in a rbtree in perf

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Date:   Thu, 14 Feb 2019 17:01:48 +0000
From:   Song Liu <songliubraving@...com>
To:     Jiri Olsa <jolsa@...hat.com>
CC:     Netdev <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "ast@...nel.org" <ast@...nel.org>,
        "daniel@...earbox.net" <daniel@...earbox.net>,
        Kernel Team <Kernel-team@...com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "acme@...hat.com" <acme@...hat.com>
Subject: Re: [PATCH 5/9] perf, bpf: save bpf_prog_info in a rbtree in perf_env



> On Feb 14, 2019, at 4:26 AM, Jiri Olsa <jolsa@...hat.com> wrote:
> 
> On Fri, Feb 08, 2019 at 05:17:01PM -0800, Song Liu wrote:
> 
> SNIP
> 
>> 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
>> 
>> #include <linux/types.h>
>> +#include <linux/rbtree.h>
>> #include "cpumap.h"
>> +#include "rwsem.h"
>> +#include "bpf-event.h"
>> 
>> 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;
> 
> why's the lock needed?
> 
> jirka

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

Let me add comments to clarify. 

Thanks,
Song