Messages in this thread Patch in this message | | | Date | Thu, 19 Sep 2013 10:16:42 +0200 | From | Peter Zijlstra <> | Subject | Re: [tip:perf/core] perf: Fix broken union in ' struct perf_event_mmap_page' |
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On Wed, Sep 18, 2013 at 04:07:52PM -0400, Vince Weaver wrote: > It would be nice if there was some way to detect this change; I liked the > idea of a "cap_usr_fixed" bit.
How about we start using the version field for this? Arguably we should have incremented that value every time we changed the thing but we might as well start now.
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diff --git a/kernel/events/core.c b/kernel/events/core.c index dd236b6..c44d55c 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -3660,6 +3660,25 @@ static void calc_timer_values(struct perf_event *event, *running = ctx_time - event->tstamp_running; } +static void perf_event_init_userpage(struct perf_event *event) +{ + struct perf_event_mmap_page *userpg; + struct ring_buffer *rb; + + rcu_read_lock(); + rb = rcu_dereference(event->rb); + if (!rb) + goto unlock; + + userpg = rb->user_page; + + userpg->version = 1; + userpg->compat_version = 0; + +unlock: + rcu_read_unlock(); +} + void __weak arch_perf_update_userpage(struct perf_event_mmap_page *userpg, u64 now) { } @@ -4044,6 +4063,7 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma) ring_buffer_attach(event, rb); rcu_assign_pointer(event->rb, rb); + perf_event_init_userpage(event); perf_event_update_userpage(event); unlock:
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