On 2015/7/17 19:56, Peter Zijlstra wrote:
On Fri, Jul 17, 2015 at 01:55:05PM +0200, Peter Zijlstra wrote:
On Fri, Jul 17, 2015 at 07:45:02PM +0800, Wangnan (F) wrote:
Depends on what all you need, if you need full perf events to work then
yes perf_event_read_value() is your only option.
But note that that requires scheduling, so you cannot actually use it
for tracing purposes etc..
What you mean "full perf events"? Even with your code some event still not
work?
The code I posted only works for events that do not have inherit set.
And only works from IRQ/NMI context for events that monitor the current
task or the current CPU (although that needs a little extra code still).
Anything else and it does not work (correctly).
Scratch that from NMI, for that to work we need more magic still.
The scheduling you said is caused by
mutex_lock(&event->child_mutex)
right?
What about replacing it to mutex_trylock() and simply return an error
if it read from a BPF program?
Thank you.
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