From: Alexei Starovoitov <ast@fb.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: "David S. Miller" <davem@davemloft.net>,
Ingo Molnar <mingo@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Wang Nan <wangnan0@huawei.com>,
Daniel Borkmann <daniel@iogearbox.net>,
Brendan Gregg <brendan.d.gregg@gmail.com>,
<netdev@vger.kernel.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH net-next 2/3] bpf: introduce BPF_MAP_TYPE_STACK_TRACE
Date: Thu, 25 Feb 2016 08:42:40 -0800 [thread overview]
Message-ID: <56CF2F00.2020608@fb.com> (raw)
In-Reply-To: <20160225142328.GN6357@twins.programming.kicks-ass.net>
On 2/25/16 6:23 AM, Peter Zijlstra wrote:
>> + id = hash & (smap->n_buckets - 1);
> Its not at all clear where the corresponding rcu_read_lock() is at.
>
>> >+ bucket = rcu_dereference(smap->buckets[id]);
bpf programs of all types are always executing under rcu_read_lock().
This is fundamental for maps and majority of the helpers
that's why there is no WARN_ON(rcu_read_lock_held) in this helper,
since we already have it in many other places.
The rcu_read_lock() for kprobe type is in trace_call_bpf().
next prev parent reply other threads:[~2016-02-25 16:43 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-18 3:58 [PATCH net-next 0/3] bpf_get_stackid() and stack_trace map Alexei Starovoitov
2016-02-18 3:58 ` [PATCH net-next 1/3] perf: generalize perf_callchain Alexei Starovoitov
2016-02-25 14:18 ` Peter Zijlstra
2016-02-25 16:37 ` Alexei Starovoitov
2016-02-25 16:45 ` Peter Zijlstra
2016-02-25 16:48 ` Peter Zijlstra
2016-02-25 16:47 ` Peter Zijlstra
2016-02-25 17:27 ` Alexei Starovoitov
2016-02-18 3:58 ` [PATCH net-next 2/3] bpf: introduce BPF_MAP_TYPE_STACK_TRACE Alexei Starovoitov
2016-02-25 14:23 ` Peter Zijlstra
2016-02-25 16:42 ` Alexei Starovoitov [this message]
2016-02-25 16:50 ` Peter Zijlstra
2016-02-18 3:58 ` [PATCH net-next 3/3] samples/bpf: offwaketime example Alexei Starovoitov
2016-02-20 5:25 ` [PATCH net-next 0/3] bpf_get_stackid() and stack_trace map David Miller
2016-02-25 14:24 ` Peter Zijlstra
2016-02-25 16:44 ` David Miller
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