diff options
| author | Peter Zijlstra <peterz@infradead.org> | 2015-01-23 11:19:48 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2015-01-28 13:17:35 +0100 |
| commit | c3c87e770458aa004bd7ed3f29945ff436fd6511 (patch) | |
| tree | 79074706175f54d333daf61cc0794aa9d76b1909 /kernel | |
| parent | ef454caeb740ee4e1b89aeb7f7692d5ddffb6830 (diff) | |
| download | linux-c3c87e770458aa004bd7ed3f29945ff436fd6511.tar.bz2 | |
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.c | 15 |
1 files changed, 13 insertions, 2 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c index 882f835a0d85..19efcf13375a 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) |