perf: Add context field to perf_event

The perf_event overflow handler does not receive any caller-derived
argument, so many callers need to resort to looking up the perf_event
in their local data structure.  This is ugly and doesn't scale if a
single callback services many perf_events.

Fix by adding a context parameter to perf_event_create_kernel_counter()
(and derived hardware breakpoints APIs) and storing it in the perf_event.
The field can be accessed from the callback as event->overflow_handler_context.
All callers are updated.

Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1309362157-6596-2-git-send-email-avi@redhat.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 1 insertions, 1 deletions

diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index a6708e677a0a..a933e3a0398b 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -375,7 +375,7 @@ static int watchdog_nmi_enable(int cpu)
         hw_nmi_watchdog_set_attr(wd_attr);
 
         /* Try to register using hardware perf events */
-        event = perf_event_create_kernel_counter(wd_attr, cpu, NULL, watchdog_overflow_callback);
+        event = perf_event_create_kernel_counter(wd_attr, cpu, NULL, watchdog_overflow_callback, NULL);
         if (!IS_ERR(event)) {
                 printk(KERN_INFO "NMI watchdog enabled, takes one hw-pmu counter.\n");
                 goto out_save;