linux-kernel - Re: [PATCH net-next 1/3] perf: generalize perf

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Message-ID: <20160225164729.GS6356@twins.programming.kicks-ass.net>
Date:	Thu, 25 Feb 2016 17:47:29 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Alexei Starovoitov <ast@...com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Ingo Molnar <mingo@...nel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Wang Nan <wangnan0@...wei.com>,
	Daniel Borkmann <daniel@...earbox.net>,
	Brendan Gregg <brendan.d.gregg@...il.com>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next 1/3] perf: generalize perf_callchain

On Wed, Feb 17, 2016 at 07:58:57PM -0800, Alexei Starovoitov wrote:
> +static inline int perf_callchain_store(struct perf_callchain_entry *entry, u64 ip)
>  {
> +	if (entry->nr < PERF_MAX_STACK_DEPTH) {
>  		entry->ip[entry->nr++] = ip;
> +		return 0;
> +	} else {
> +		return -1; /* no more room, stop walking the stack */
> +	}
>  }

Why 0 and -1 ?

What's wrong with something like:

static inline bool perf_callchain_store(struct perf_callchain_entry *entry, u64 ip)
{
	if (entry->nr < PERF_MAX_STACK_DEPTH) {
		entry->ip[entry->nr++] = ip;
		return true;
	}
	return false;
}