From: Daniel Borkmann <daniel@iogearbox.net>
To: Yonghong Song <yhs@fb.com>,
peterz@infradead.org, rostedt@goodmis.org, ast@fb.com,
kafai@fb.com, netdev@vger.kernel.org
Cc: kernel-team@fb.com
Subject: Re: [PATCH net-next 2/3] bpf: permit multiple bpf attachments for a single perf event
Date: Mon, 23 Oct 2017 22:52:29 +0200 [thread overview]
Message-ID: <59EE568D.7040204@iogearbox.net> (raw)
In-Reply-To: <20171023175805.2898366-3-yhs@fb.com>
On 10/23/2017 07:58 PM, Yonghong Song wrote:
[...]
> __this_cpu_dec(bpf_prog_active);
> @@ -741,3 +754,63 @@ const struct bpf_verifier_ops perf_event_verifier_ops = {
>
> const struct bpf_prog_ops perf_event_prog_ops = {
> };
> +
> +static DEFINE_MUTEX(bpf_event_mutex);
> +
> +int perf_event_attach_bpf_prog(struct perf_event *event,
> + struct bpf_prog *prog)
> +{
> + struct bpf_prog_array __rcu *old_array;
> + struct bpf_prog_array *new_array;
> + int ret;
> +
> + mutex_lock(&bpf_event_mutex);
> +
> + if (event->prog)
> + return -EEXIST;
Needs to go to out here, otherwise deadlock.
> +
> + old_array = rcu_dereference_protected(event->tp_event->prog_array,
> + lockdep_is_held(&bpf_event_mutex));
> + ret = bpf_prog_array_copy(old_array, NULL, prog, &new_array);
> + if (ret < 0)
> + goto out;
> +
> + /* set the new array to event->tp_event and set event->prog */
> + event->prog = prog;
> + rcu_assign_pointer(event->tp_event->prog_array, new_array);
> +
> + if (old_array)
> + bpf_prog_array_free(old_array);
> +
> +out:
> + mutex_unlock(&bpf_event_mutex);
> + return ret;
> +}
> +
> +void perf_event_detach_bpf_prog(struct perf_event *event)
> +{
> + struct bpf_prog_array __rcu *old_array;
> + struct bpf_prog_array *new_array;
> + int ret;
> +
> + mutex_lock(&bpf_event_mutex);
> +
> + if (!event->prog)
> + return;
Ditto.
> +
> + old_array = rcu_dereference_protected(event->tp_event->prog_array,
> + lockdep_is_held(&bpf_event_mutex));
> +
> + ret = bpf_prog_array_copy(old_array, event->prog, NULL, &new_array);
> + if (ret < 0) {
> + bpf_prog_array_delete_safe(old_array, event->prog);
> + } else {
> + rcu_assign_pointer(event->tp_event->prog_array, new_array);
> + bpf_prog_array_free(old_array);
> + }
> +
> + bpf_prog_put(event->prog);
> + event->prog = NULL;
> +
> + mutex_unlock(&bpf_event_mutex);
> +}
[...]
next prev parent reply other threads:[~2017-10-23 20:52 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-23 17:58 [PATCH net-next 0/3] bpf: permit multiple bpf attachments for a single perf tracepoint event Yonghong Song
2017-10-23 17:58 ` [PATCH net-next 1/3] bpf: use the same condition in perf event set/free bpf handler Yonghong Song
2017-10-23 17:58 ` [PATCH net-next 2/3] bpf: permit multiple bpf attachments for a single perf event Yonghong Song
2017-10-23 20:52 ` Daniel Borkmann [this message]
2017-10-23 21:00 ` Yonghong Song
2017-10-24 4:05 ` kbuild test robot
2017-10-24 4:07 ` kbuild test robot
2017-10-25 16:18 ` [lkp-robot] [bpf] 76cdd39f41: WARNING:trinity-c0_still_has_locks_held kernel test robot
2017-10-30 21:57 ` Yonghong Song
2017-10-26 13:56 ` [PATCH net-next 2/3] bpf: permit multiple bpf attachments for a single perf event Peter Zijlstra
2017-10-26 16:42 ` Yonghong Song
2017-10-23 17:58 ` [PATCH net-next 3/3] bpf: add a test case to test single tp multiple bpf attachment Yonghong Song
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