Commit-ID: 99e818cc88889a2fa2f483b91b372c47b94b7c98
Gitweb: https://git.kernel.org/tip/99e818cc88889a2fa2f483b91b372c47b94b7c98
Author: Jiri Olsa <jolsa@xxxxxxxxxx>
AuthorDate: Sun, 7 Jan 2018 17:03:50 +0100
Committer: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
CommitDate: Mon, 8 Jan 2018 12:35:01 -0300
perf: Return empty callchain instead of NULL
It simplifies the code a bit, because we dump the callchain
Link: http://lkml.kernel.org/n/tip-uqp7qd6aif47g39glnbu95yl@xxxxxxxxxxxxxx
even if it's empty. With 'empty' callchain we can remove
all the NULL-checking code paths.
Original-patch-from: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Cc: David Ahern <dsahern@xxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Link: http://lkml.kernel.org/r/20180107160356.28203-7-jolsa@xxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
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 5fc1ded..4e1a1bf 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);
}
--
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