From: Jiri Olsa <jolsa@kernel.org>
To: Arnaldo Carvalho de Melo <acme@kernel.org>,
Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: lkml <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@kernel.org>,
Namhyung Kim <namhyung@kernel.org>,
David Ahern <dsahern@gmail.com>, Andi Kleen <ak@linux.intel.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>
Subject: [PATCH 06/12] perf: Return empty callchain instead of NULL
Date: Sun, 7 Jan 2018 17:03:50 +0100 [thread overview]
Message-ID: <20180107160356.28203-7-jolsa@kernel.org> (raw)
In-Reply-To: <20180107160356.28203-1-jolsa@kernel.org>
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 <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-n4t869o2qc1b31v4wwvmxznb@git.kernel.org
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
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
next prev parent reply other threads:[~2018-01-07 16:04 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-07 16:03 [PATCH 00/12] perf: Assorted fixes Jiri Olsa
2018-01-07 16:03 ` [PATCH 01/12] perf tools: Enable LIBBABELTRACE by default Jiri Olsa
2018-01-08 15:17 ` Arnaldo Carvalho de Melo
2018-01-08 15:20 ` Arnaldo Carvalho de Melo
2018-01-08 15:24 ` Arnaldo Carvalho de Melo
2018-01-08 17:11 ` Jiri Olsa
2018-01-08 17:16 ` Jiri Olsa
2018-01-09 9:26 ` [PATCH] perf build: Display EXTRA features for VF=1 build Jiri Olsa
2018-01-19 10:15 ` Jiri Olsa
2018-01-19 12:43 ` Arnaldo Carvalho de Melo
2018-01-24 11:23 ` [tip:perf/core] " tip-bot for Jiri Olsa
2018-01-11 6:24 ` [tip:perf/core] perf tools: Enable LIBBABELTRACE by default tip-bot for Jiri Olsa
2018-01-07 16:03 ` [PATCH 02/12] perf tools: Display perf_event_attr::namespaces debug info Jiri Olsa
2018-01-11 6:24 ` [tip:perf/core] " tip-bot for Jiri Olsa
2018-01-07 16:03 ` [PATCH 03/12] perf: Allocate context task_ctx_data for child event Jiri Olsa
2018-01-08 12:14 ` Peter Zijlstra
2018-01-11 6:24 ` [tip:perf/core] " tip-bot for Jiri Olsa
2018-01-07 16:03 ` [PATCH 04/12] perf: Add sample_id to PERF_RECORD_ITRACE_START event comment Jiri Olsa
2018-01-11 6:25 ` [tip:perf/core] " tip-bot for Jiri Olsa
2018-01-07 16:03 ` [PATCH 05/12] perf: Make perf_callchain function static Jiri Olsa
2018-01-11 6:25 ` [tip:perf/core] " tip-bot for Jiri Olsa
2018-01-07 16:03 ` Jiri Olsa [this message]
2018-01-08 12:15 ` [PATCH 06/12] perf: Return empty callchain instead of NULL Peter Zijlstra
2018-01-11 6:26 ` [tip:perf/core] " tip-bot for Jiri Olsa
2018-01-07 16:03 ` [PATCH 07/12] perf: Update PERF_RECORD_MISC_* comment for perf_event_header::misc bit 13 Jiri Olsa
2018-01-11 6:26 ` [tip:perf/core] " tip-bot for Jiri Olsa
2018-01-07 16:03 ` [PATCH 08/12] perf script: Add support to display sample misc field Jiri Olsa
2018-01-11 6:27 ` [tip:perf/core] " tip-bot for Jiri Olsa
2018-01-07 16:03 ` [PATCH 09/12] perf script: Add support to display lost events Jiri Olsa
2018-01-10 15:40 ` Arnaldo Carvalho de Melo
2018-01-10 15:44 ` Jiri Olsa
2018-01-11 6:27 ` [tip:perf/core] " tip-bot for Jiri Olsa
2018-01-07 16:03 ` [PATCH 10/12] perf tools: Make the tool's warning messages optional Jiri Olsa
2018-01-11 6:27 ` [tip:perf/core] " tip-bot for Jiri Olsa
2018-01-07 16:03 ` [PATCH 11/12] perf report: Add --stat option to display quick data statistics Jiri Olsa
2018-01-11 6:28 ` [tip:perf/core] perf report: Add --stats " tip-bot for Jiri Olsa
2018-01-07 16:03 ` [PATCH 12/12] perf report: Add --task option to display monitored tasks Jiri Olsa
2018-01-08 15:55 ` Arnaldo Carvalho de Melo
2018-01-08 16:03 ` Arnaldo Carvalho de Melo
2018-01-09 1:56 ` Namhyung Kim
2018-01-09 9:15 ` Jiri Olsa
2018-01-09 13:05 ` Arnaldo Carvalho de Melo
2018-01-09 13:27 ` Jiri Olsa
2018-01-11 6:29 ` [tip:perf/core] perf report: Add --tasks " tip-bot for Jiri Olsa
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