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| author | Jiri Olsa <jolsa@kernel.org> | 2018-01-07 17:03:50 +0100 |
|---|---|---|
| committer | Arnaldo Carvalho de Melo <acme@redhat.com> | 2018-01-08 12:35:01 -0300 |
| commit | 99e818cc88889a2fa2f483b91b372c47b94b7c98 (patch) | |
| tree | e015ff4014a41fca03a550187172bd1e4448150c /kernel/events | |
| parent | 8cf7e0e22414f5acf85ecb7cd0d4482e6c9696ae (diff) | |
| download | linux-stable-99e818cc88889a2fa2f483b91b372c47b94b7c98.tar.gz linux-stable-99e818cc88889a2fa2f483b91b372c47b94b7c98.tar.bz2 linux-stable-99e818cc88889a2fa2f483b91b372c47b94b7c98.zip | |
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@git.kernel.org
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>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/r/20180107160356.28203-7-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Diffstat (limited to 'kernel/events')
| -rw-r--r-- | kernel/events/core.c | 30 |
1 files 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); } |