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authorPeter Zijlstra <peterz@infradead.org>2015-01-23 11:19:48 +0100
committerIngo Molnar <mingo@kernel.org>2015-01-28 13:17:35 +0100
commitc3c87e770458aa004bd7ed3f29945ff436fd6511 (patch)
tree79074706175f54d333daf61cc0794aa9d76b1909 /kernel
parentef454caeb740ee4e1b89aeb7f7692d5ddffb6830 (diff)
downloadop-kernel-dev-c3c87e770458aa004bd7ed3f29945ff436fd6511.zip
op-kernel-dev-c3c87e770458aa004bd7ed3f29945ff436fd6511.tar.gz
perf: Tighten (and fix) the grouping condition
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 in practice as well by me via the perf 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> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/20150123125834.090683288@infradead.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/events/core.c15
1 files changed, 13 insertions, 2 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 882f835..19efcf1 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -6776,7 +6776,6 @@ skip_type:
__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);
@@ -7420,7 +7419,19 @@ 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)
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