Messages in this thread | | | Date | Thu, 23 Jun 2011 10:38:54 -0400 | From | Eric B Munson <> | Subject | Re: [PATCH] events: Ensure that timers are updated without requiring read() call |
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On Thu, 23 Jun 2011, Peter Zijlstra wrote:
> On Thu, 2011-06-23 at 10:15 -0400, Eric B Munson wrote: > > The event tracing infrastructure exposes two timers which should be updated > > each time the value of the counter is updated. Currently, these counters are > > only updated when userspace calls read() on the fd associated with an event. > > This means that counters which are read via the mmap'd page exclusively never > > have their timers updated. This patch adds ensures that the timers are updated > > each time the values in the mmap'd page are updated. > > > > Signed-off-by: Eric B Munson <emunson@mgebm.net> > > --- > > kernel/events/core.c | 1 + > > 1 files changed, 1 insertions(+), 0 deletions(-) > > > > diff --git a/kernel/events/core.c b/kernel/events/core.c > > index 9efe710..3dd4ebe 100644 > > --- a/kernel/events/core.c > > +++ b/kernel/events/core.c > > @@ -3369,6 +3369,7 @@ void perf_event_update_userpage(struct perf_event *event) > > struct perf_buffer *buffer; > > > > rcu_read_lock(); > > + update_event_times(event); > > buffer = rcu_dereference(event->buffer); > > if (!buffer) > > goto unlock; > > Not that easy, perf_event_update_userpage() can happen from NMI context, > and update_event_times() needs to be done under ctx->lock. >
I was afraid that might be the case, is there an easy-ish way to accomplish the timer update?
Eric [unhandled content-type:application/pgp-signature] | |