yes, you are right. In my cases, there also are some issues in
add_event_to_ctx(),
I am gonna fix it at v2
Thanks
2018-01-24 0:37 GMT+08:00 Peter Zijlstra <pet...@infradead.org>:
> On Tue, Jan 23, 2018 at 12:13:06PM +0800, linxiu...@gmail.com wrote:
>> From: "leilei.lin" <leilei....@alibaba-inc.com>
>>
>> Do not install cgroup event into the CPU context if the cgroup
>> is not running on this CPU
>>
>> While there is no task of cgroup running specified CPU, current
>> kernel still install cgroup event into CPU context, that causes
>> another cgroup event can't be installed into this CPU.
>>
>> Signed-off-by: leilei.lin <leilei....@alibaba-inc.com>
>> ---
>> kernel/events/core.c | 14 ++++++++++++++
>> 1 file changed, 14 insertions(+)
>>
>> diff --git a/kernel/events/core.c b/kernel/events/core.c
>> index 4df5b69..19c587b 100644
>> --- a/kernel/events/core.c
>> +++ b/kernel/events/core.c
>> @@ -2284,6 +2284,7 @@ static int __perf_install_in_context(void *info)
>> struct perf_event_context *ctx = event->ctx;
>> struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);
>> struct perf_event_context *task_ctx = cpuctx->task_ctx;
>> + struct perf_cgroup *cgrp;
>> bool reprogram = true;
>> int ret = 0;
>>
>> @@ -2311,6 +2312,19 @@ static int __perf_install_in_context(void *info)
>> raw_spin_lock(&task_ctx->lock);
>> }
>>
>> + if (event->cgrp) {
>> + /*
>> + * Only care about cgroup events.
>> + *
>> + * If only the task belongs to cgroup of this event,
>> + * we will continue the installment
>> + */
>> + cgrp = perf_cgroup_from_task(current, ctx);
>> + if (!cgroup_is_descendant(cgrp->css.cgroup,
>> + event->cgrp->css.cgroup))
>> + goto unlock;
>> + }
>> +
>> if (reprogram) {
>> ctx_sched_out(ctx, cpuctx, EVENT_TIME);
>> add_event_to_ctx(event, ctx);
>
> I think this is wrong. You're right in that we need not schedule it not,
> but the above also completely fails to add it to the context, leading to
> it never being scheduled ever.
>
> At the very least we should do add_event_to_ctx() on it.
>
> So the only thing you can do is pick 'reprogram' or not based on if the
> current cgrp is related to the event->ctx.
