This is a note to let you know that I've just added the patch titled
perf/core: Correct event creation with PERF_FORMAT_GROUP
to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
perf-core-correct-event-creation-with-perf_format_group.patch
and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Mon Apr 9 17:09:24 CEST 2018
From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Date: Tue, 30 May 2017 11:45:12 +0200
Subject: perf/core: Correct event creation with PERF_FORMAT_GROUP
From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
[ Upstream commit ba5213ae6b88fb170c4771fef6553f759c7d8cdd ]
Andi was asking about PERF_FORMAT_GROUP vs inherited events, which led
to the discovery of a bug from commit:
3dab77fb1bf8 ("perf: Rework/fix the whole read vs group stuff")
- PERF_SAMPLE_GROUP = 1U << 4,
+ PERF_SAMPLE_READ = 1U << 4,
- if (attr->inherit && (attr->sample_type & PERF_SAMPLE_GROUP))
+ if (attr->inherit && (attr->read_format & PERF_FORMAT_GROUP))
is a clear fail :/
While this changes user visible behaviour; it was previously possible
to create an inherited event with PERF_SAMPLE_READ; this is deemed
acceptible because its results were always incorrect.
Reported-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Stephane Eranian <eranian@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Vince Weaver <vince@xxxxxxxxxx>
Fixes: 3dab77fb1bf8 ("perf: Rework/fix the whole read vs group stuff")
Link: http://lkml.kernel.org/r/20170530094512.dy2nljns2uq7qa3j@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/events/core.c | 15 ++++++++++-----
1 file changed, 10 insertions(+), 5 deletions(-)
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -5669,9 +5669,6 @@ static void perf_output_read_one(struct
__output_copy(handle, values, n * sizeof(u64));
}
-/*
- * XXX PERF_FORMAT_GROUP vs inherited events seems difficult.
- */
static void perf_output_read_group(struct perf_output_handle *handle,
struct perf_event *event,
u64 enabled, u64 running)
@@ -5716,6 +5713,13 @@ static void perf_output_read_group(struc
#define PERF_FORMAT_TOTAL_TIMES (PERF_FORMAT_TOTAL_TIME_ENABLED|\
PERF_FORMAT_TOTAL_TIME_RUNNING)
+/*
+ * XXX PERF_SAMPLE_READ vs inherited events seems difficult.
+ *
+ * The problem is that its both hard and excessively expensive to iterate the
+ * child list, not to mention that its impossible to IPI the children running
+ * on another CPU, from interrupt/NMI context.
+ */
static void perf_output_read(struct perf_output_handle *handle,
struct perf_event *event)
{
@@ -9259,9 +9263,10 @@ perf_event_alloc(struct perf_event_attr
local64_set(&hwc->period_left, hwc->sample_period);
/*
- * we currently do not support PERF_FORMAT_GROUP on inherited events
+ * We currently do not support PERF_SAMPLE_READ on inherited events.
+ * See perf_output_read().
*/
- if (attr->inherit && (attr->read_format & PERF_FORMAT_GROUP))
+ if (attr->inherit && (attr->sample_type & PERF_SAMPLE_READ))
goto err_ns;
if (!has_branch_stack(event))
Patches currently in stable-queue which might be from peterz@xxxxxxxxxxxxx are
queue-4.9/perf-callchain-force-user_ds-when-invoking-perf_callchain_user.patch
queue-4.9/perf-report-fix-off-by-one-for-non-activation-frames.patch
queue-4.9/x86-efi-disable-runtime-services-on-kexec-kernel-if-booted-with-efi-old_map.patch
queue-4.9/perf-tools-fix-copyfile_offset-update-of-output-offset.patch
queue-4.9/sched-numa-use-down_read_trylock-for-the-mmap_sem.patch
queue-4.9/x86-asm-don-t-use-rbp-as-a-temporary-register-in-csum_partial_copy_generic.patch
queue-4.9/perf-core-correct-event-creation-with-perf_format_group.patch
queue-4.9/x86-mm-kaslr-use-the-_asm_mul-macro-for-multiplication-to-work-around-clang-incompatibility.patch
queue-4.9/x86-tsc-provide-tsc-unstable-boot-parameter.patch
queue-4.9/x86-boot-declare-error-as-noreturn.patch
queue-4.9/cpuhotplug-link-lock-stacks-for-hotplug-callbacks.patch
queue-4.9/perf-core-fix-error-handling-in-perf_event_alloc.patch
queue-4.9/sched-deadline-use-the-revised-wakeup-rule-for-suspending-constrained-dl-tasks.patch