From: Peter Zijlstra <peterz@infradead.org>
To: mingo@kernel.org, linux-kernel@vger.kernel.org
Cc: vincent.weaver@maine.edu, eranian@gmail.com, jolsa@redhat.com,
mark.rutland@arm.com, torvalds@linux-foundation.org,
tglx@linutronix.de, peterz@infradead.org
Subject: [RFC][PATCH 1/3] perf: Tighten (and fix) the grouping condition
Date: Fri, 23 Jan 2015 13:52:00 +0100 [thread overview]
Message-ID: <20150123125834.090683288@infradead.org> (raw)
In-Reply-To: 20150123125159.696530128@infradead.org
[-- Attachment #1: peterz-perf-fix-grouping.patch --]
[-- Type: text/plain, Size: 2413 bytes --]
The fix from 9fc81d87420d ("perf: Fix events installation during
moving group") was incomplete in that it failed to recognise that
creating a group with events for different CPUs is semantically
broken -- they cannot be co-scheduled.
Furthermore, it leads to real breakage where, when we create an event
for CPU Y and then migrate it to form a group on CPU X, the code gets
confused where the counter is programmed -- triggered by the fuzzer.
Fix this by tightening the rules for creating groups. Only allow
grouping of counters that can be co-scheduled in the same context.
This means for the same task and/or the same cpu.
Fixes: 9fc81d87420d ("perf: Fix events installation during moving group")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
include/linux/perf_event.h | 6 ------
kernel/events/core.c | 15 +++++++++++++--
2 files changed, 13 insertions(+), 8 deletions(-)
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -450,11 +450,6 @@ struct perf_event {
#endif /* CONFIG_PERF_EVENTS */
};
-enum perf_event_context_type {
- task_context,
- cpu_context,
-};
-
/**
* struct perf_event_context - event context structure
*
@@ -462,7 +457,6 @@ enum perf_event_context_type {
*/
struct perf_event_context {
struct pmu *pmu;
- enum perf_event_context_type type;
/*
* Protect the states of the events in the list,
* nr_active, and the list:
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -6846,7 +6846,6 @@ int perf_pmu_register(struct pmu *pmu, c
__perf_event_init_context(&cpuctx->ctx);
lockdep_set_class(&cpuctx->ctx.mutex, &cpuctx_mutex);
lockdep_set_class(&cpuctx->ctx.lock, &cpuctx_lock);
- cpuctx->ctx.type = cpu_context;
cpuctx->ctx.pmu = pmu;
__perf_cpu_hrtimer_init(cpuctx, cpu);
@@ -7493,7 +7492,19 @@ SYSCALL_DEFINE5(perf_event_open,
* task or CPU context:
*/
if (move_group) {
- if (group_leader->ctx->type != ctx->type)
+ /*
+ * Make sure we're both on the same task, or both
+ * per-cpu events.
+ */
+ if (group_leader->ctx->task != ctx->task)
+ goto err_context;
+
+ /*
+ * Make sure we're both events for the same CPU;
+ * grouping events for different CPUs is broken; since
+ * you can never concurrently schedule them anyhow.
+ */
+ if (group_leader->cpu != event->cpu)
goto err_context;
} else {
if (group_leader->ctx != ctx)
next prev parent reply other threads:[~2015-01-23 13:00 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-23 12:51 [RFC][PATCH 0/3] perf fixes Peter Zijlstra
2015-01-23 12:52 ` Peter Zijlstra [this message]
2015-01-23 15:02 ` [RFC][PATCH 1/3] perf: Tighten (and fix) the grouping condition Mark Rutland
2015-01-23 15:07 ` Peter Zijlstra
2015-01-23 15:22 ` Mark Rutland
2015-02-04 12:59 ` Peter Zijlstra
2015-01-28 14:30 ` [tip:perf/urgent] " tip-bot for Peter Zijlstra
2015-01-23 12:52 ` [RFC][PATCH 2/3] perf: Add a bit of paranoia Peter Zijlstra
2015-01-26 16:26 ` Peter Zijlstra
2015-01-27 21:28 ` Vince Weaver
2015-01-29 2:16 ` Vince Weaver
2015-01-29 7:51 ` Jiri Olsa
2015-01-29 13:44 ` Peter Zijlstra
2015-02-04 14:39 ` [tip:perf/core] perf: Fix put_event() ctx lock tip-bot for Peter Zijlstra
2015-01-29 14:47 ` [RFC][PATCH 2/3] perf: Add a bit of paranoia Peter Zijlstra
2015-02-02 6:33 ` Vince Weaver
2015-02-02 15:42 ` Peter Zijlstra
2015-02-02 17:32 ` Peter Zijlstra
2015-02-04 14:51 ` Jiri Olsa
2015-02-04 16:33 ` Peter Zijlstra
2015-02-04 16:43 ` Peter Zijlstra
2015-02-04 14:39 ` [tip:perf/core] perf: Fix move_group() order tip-bot for Peter Zijlstra (Intel)
2015-02-04 14:39 ` [tip:perf/core] perf: Add a bit of paranoia tip-bot for Peter Zijlstra
2015-01-23 12:52 ` [RFC][PATCH 3/3] perf: Fix event->ctx locking Peter Zijlstra
2015-02-04 14:39 ` [tip:perf/core] " tip-bot for Peter Zijlstra
2015-01-26 14:30 ` [RFC][PATCH 0/3] perf fixes Vince Weaver
2015-01-26 18:03 ` Vince Weaver
2015-01-26 18:34 ` Jiri Olsa
2015-01-26 18:52 ` Vince Weaver
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