From mboxrd@z Thu Jan 1 00:00:00 1970 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754179AbeAGQET (ORCPT + 1 other); Sun, 7 Jan 2018 11:04:19 -0500 Received: from mx1.redhat.com ([209.132.183.28]:34728 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754130AbeAGQEQ (ORCPT ); Sun, 7 Jan 2018 11:04:16 -0500 From: Jiri Olsa To: Arnaldo Carvalho de Melo , Peter Zijlstra Cc: lkml , Ingo Molnar , Namhyung Kim , David Ahern , Andi Kleen , Alexander Shishkin Subject: [PATCH 06/12] perf: Return empty callchain instead of NULL Date: Sun, 7 Jan 2018 17:03:50 +0100 Message-Id: <20180107160356.28203-7-jolsa@kernel.org> In-Reply-To: <20180107160356.28203-1-jolsa@kernel.org> References: <20180107160356.28203-1-jolsa@kernel.org> X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Sun, 07 Jan 2018 16:04:16 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: It simplifies the code a bit, because we dump the callchain even if it's empty. With 'empty' callchain we can remove all the NULL-checking code paths. Original-patch-from: Peter Zijlstra Link: http://lkml.kernel.org/n/tip-n4t869o2qc1b31v4wwvmxznb@git.kernel.org Signed-off-by: Jiri Olsa --- kernel/events/core.c | 30 ++++++++++++------------------ 1 file changed, 12 insertions(+), 18 deletions(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index 5fc1ded4b450..4e1a1bf8d867 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -5815,19 +5815,11 @@ void perf_output_sample(struct perf_output_handle *handle, perf_output_read(handle, event); if (sample_type & PERF_SAMPLE_CALLCHAIN) { - if (data->callchain) { - int size = 1; - - if (data->callchain) - size += data->callchain->nr; - - size *= sizeof(u64); + int size = 1; - __output_copy(handle, data->callchain, size); - } else { - u64 nr = 0; - perf_output_put(handle, nr); - } + size += data->callchain->nr; + size *= sizeof(u64); + __output_copy(handle, data->callchain, size); } if (sample_type & PERF_SAMPLE_RAW) { @@ -5980,6 +5972,8 @@ static u64 perf_virt_to_phys(u64 virt) return phys_addr; } +static struct perf_callchain_entry __empty_callchain = { .nr = 0, }; + static struct perf_callchain_entry * perf_callchain(struct perf_event *event, struct pt_regs *regs) { @@ -5988,12 +5982,14 @@ perf_callchain(struct perf_event *event, struct pt_regs *regs) /* Disallow cross-task user callchains. */ bool crosstask = event->ctx->task && event->ctx->task != current; const u32 max_stack = event->attr.sample_max_stack; + struct perf_callchain_entry *callchain; if (!kernel && !user) - return NULL; + return &__empty_callchain; - return get_perf_callchain(regs, 0, kernel, user, - max_stack, crosstask, true); + callchain = get_perf_callchain(regs, 0, kernel, user, + max_stack, crosstask, true); + return callchain ?: &__empty_callchain; } void perf_prepare_sample(struct perf_event_header *header, @@ -6018,9 +6014,7 @@ void perf_prepare_sample(struct perf_event_header *header, int size = 1; data->callchain = perf_callchain(event, regs); - - if (data->callchain) - size += data->callchain->nr; + size += data->callchain->nr; header->size += size * sizeof(u64); } -- 2.13.6