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From: Peter Zijlstra <peterz@infradead.org>
To: Song Liu <songliubraving@fb.com>
Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org,
	acme@kernel.org, mingo@redhat.com, kjain@linux.ibm.com,
	kernel-team@fb.com
Subject: Re: [PATCH v2 bpf-next 1/3] perf: enable branch record for software events
Date: Mon, 30 Aug 2021 12:22:58 +0200	[thread overview]
Message-ID: <20210830102258.GI4353@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <20210826221306.2280066-2-songliubraving@fb.com>

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)(...);

?

  reply	other threads:[~2021-08-30 10:25 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 [this message]
2021-08-30 15:25     ` Song Liu
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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