From: Song Liu <songliubraving@fb.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: "open list:BPF (Safe dynamic programs and tools)"
<bpf@vger.kernel.org>, LKML <linux-kernel@vger.kernel.org>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Ingo Molnar <mingo@redhat.com>, kajoljain <kjain@linux.ibm.com>,
Kernel Team <Kernel-team@fb.com>
Subject: Re: [PATCH v2 bpf-next 1/3] perf: enable branch record for software events
Date: Mon, 30 Aug 2021 15:25:44 +0000 [thread overview]
Message-ID: <F70BD5BE-C698-4C53-9ECD-A4805CB2D659@fb.com> (raw)
In-Reply-To: <20210830102258.GI4353@worktop.programming.kicks-ass.net>
> On Aug 30, 2021, at 3:22 AM, Peter Zijlstra <peterz@infradead.org> wrote:
>
> On Thu, Aug 26, 2021 at 03:13:04PM -0700, Song Liu wrote:
>> +int dummy_perf_snapshot_branch_stack(struct perf_branch_snapshot *br_snapshot);
>> +
>> +DECLARE_STATIC_CALL(perf_snapshot_branch_stack, dummy_perf_snapshot_branch_stack);
>> +
>> #endif /* _LINUX_PERF_EVENT_H */
>> diff --git a/kernel/events/core.c b/kernel/events/core.c
>> index 011cc5069b7ba..c53fe90e630ac 100644
>> --- a/kernel/events/core.c
>> +++ b/kernel/events/core.c
>> @@ -13437,3 +13437,6 @@ struct cgroup_subsys perf_event_cgrp_subsys = {
>> .threaded = true,
>> };
>> #endif /* CONFIG_CGROUP_PERF */
>> +
>> +DEFINE_STATIC_CALL_NULL(perf_snapshot_branch_stack,
>> + dummy_perf_snapshot_branch_stack);
>
> This isn't right...
>
> The whole dummy_perf_snapshot_branch_stack() thing is a declaration only
> and used as a typedef. Also, DEFINE_STATIC_CALL_NULL() and
> static_call_cond() rely on a void return value, which it doesn't have.
>
> Did you want:
>
> DECLARE_STATIC_CALL(perf_snapshot_branch_stack, void (*)(struct perf_branch_snapshot *));
>
> DEFINE_STATIC_CALL_NULL(perf_snapshot_branch_stack, void (*)(struct perf_branch_snapshot *));
>
> static_call_cond(perf_snapshot_branch_stack)(...);
>
> *OR*, do you actually need that return value, in which case you're
> probably looking for:
>
> DECLARE_STATIC_CALL(perf_snapshot_branch_stack, int (*)(struct perf_branch_snapshot *));
>
> DEFINE_STATIC_CALL_RET0(perf_snapshot_branch_stack, int (*)(struct perf_branch_snapshot *));
>
> ret = static_call(perf_snapshot_branch_stack)(...);
>
> ?
Thanks for these information! I did get confused these macros for quite a
while. Let me try with the _RET0 version.
Song
next prev parent reply other threads:[~2021-08-30 15:25 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-26 22:13 [PATCH v2 bpf-next 0/3] bpf: introduce bpf_get_branch_snapshot Song Liu
2021-08-26 22:13 ` [PATCH v2 bpf-next 1/3] perf: enable branch record for software events Song Liu
2021-08-30 10:22 ` Peter Zijlstra
2021-08-30 15:25 ` Song Liu [this message]
2021-08-30 16:06 ` Peter Zijlstra
2021-08-30 16:36 ` Song Liu
2021-09-01 17:09 ` Peter Zijlstra
2021-08-30 17:41 ` Song Liu
2021-08-30 18:07 ` Peter Zijlstra
2021-09-01 17:12 ` Peter Zijlstra
2021-09-04 23:01 ` Josh Poimboeuf
2021-08-30 10:43 ` Peter Zijlstra
2021-08-30 16:06 ` Song Liu
2021-08-26 22:13 ` [PATCH v2 bpf-next 2/3] bpf: introduce helper bpf_get_branch_snapshot Song Liu
2021-08-27 9:28 ` kernel test robot
2021-08-27 15:10 ` kernel test robot
2021-08-30 10:47 ` Peter Zijlstra
2021-08-26 22:13 ` [PATCH v2 bpf-next 3/3] selftests/bpf: add test for bpf_get_branch_snapshot Song Liu
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