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>

2 files changed, 22 insertions, 9 deletions

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 81de28dcca8c..ba8e0f4a20e6 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -5745,7 +5745,8 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,
                  struct task_struct *task,
                  struct perf_event *group_leader,
                  struct perf_event *parent_event,
-                 perf_overflow_handler_t overflow_handler)
+                 perf_overflow_handler_t overflow_handler,
+                 void *context)
 {
         struct pmu *pmu;
         struct perf_event *event;
@@ -5803,10 +5804,13 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,
 #endif
         }
 
-        if (!overflow_handler && parent_event)
+        if (!overflow_handler && parent_event) {
                 overflow_handler = parent_event->overflow_handler;
+                context = parent_event->overflow_handler_context;
+        }
 
         event->overflow_handler = overflow_handler;
+        event->overflow_handler_context = context;
 
         if (attr->disabled)
                 event->state = PERF_EVENT_STATE_OFF;
@@ -6073,7 +6077,8 @@ SYSCALL_DEFINE5(perf_event_open,
                 }
         }
 
-        event = perf_event_alloc(&attr, cpu, task, group_leader, NULL, NULL);
+        event = perf_event_alloc(&attr, cpu, task, group_leader, NULL,
+                                 NULL, NULL);
         if (IS_ERR(event)) {
                 err = PTR_ERR(event);
                 goto err_task;
@@ -6258,7 +6263,8 @@ err_fd:
 struct perf_event *
 perf_event_create_kernel_counter(struct perf_event_attr *attr, int cpu,
                                  struct task_struct *task,
-                                 perf_overflow_handler_t overflow_handler)
+                                 perf_overflow_handler_t overflow_handler,
+                                 void *context)
 {
         struct perf_event_context *ctx;
         struct perf_event *event;
@@ -6268,7 +6274,8 @@ perf_event_create_kernel_counter(struct perf_event_attr *attr, int cpu,
          * Get the target context (task or percpu):
          */
 
-        event = perf_event_alloc(attr, cpu, task, NULL, NULL, overflow_handler);
+        event = perf_event_alloc(attr, cpu, task, NULL, NULL,
+                                 overflow_handler, context);
         if (IS_ERR(event)) {
                 err = PTR_ERR(event);
                 goto err;
@@ -6552,7 +6559,7 @@ inherit_event(struct perf_event *parent_event,
                                            parent_event->cpu,
                                            child,
                                            group_leader, parent_event,
-                                           NULL);
+                                           NULL, NULL);
         if (IS_ERR(child_event))
                 return child_event;
         get_ctx(child_ctx);
@@ -6579,6 +6586,8 @@ inherit_event(struct perf_event *parent_event,
 
         child_event->ctx = child_ctx;
         child_event->overflow_handler = parent_event->overflow_handler;
+        child_event->overflow_handler_context
+                = parent_event->overflow_handler_context;
 
         /*
          * Precalculate sample_data sizes
diff --git a/kernel/events/hw_breakpoint.c b/kernel/events/hw_breakpoint.c
index 086adf25a55e..b7971d6f38bf 100644
--- a/kernel/events/hw_breakpoint.c
+++ b/kernel/events/hw_breakpoint.c
@@ -431,9 +431,11 @@ int register_perf_hw_breakpoint(struct perf_event *bp)
 struct perf_event *
 register_user_hw_breakpoint(struct perf_event_attr *attr,
                             perf_overflow_handler_t triggered,
+                            void *context,
                             struct task_struct *tsk)
 {
-        return perf_event_create_kernel_counter(attr, -1, tsk, triggered);
+        return perf_event_create_kernel_counter(attr, -1, tsk, triggered,
+                                                context);
 }
 EXPORT_SYMBOL_GPL(register_user_hw_breakpoint);
 
@@ -502,7 +504,8 @@ EXPORT_SYMBOL_GPL(unregister_hw_breakpoint);
  */
 struct perf_event * __percpu *
 register_wide_hw_breakpoint(struct perf_event_attr *attr,
-                            perf_overflow_handler_t triggered)
+                            perf_overflow_handler_t triggered,
+                            void *context)
 {
         struct perf_event * __percpu *cpu_events, **pevent, *bp;
         long err;
@@ -515,7 +518,8 @@ register_wide_hw_breakpoint(struct perf_event_attr *attr,
         get_online_cpus();
         for_each_online_cpu(cpu) {
                 pevent = per_cpu_ptr(cpu_events, cpu);
-                bp = perf_event_create_kernel_counter(attr, cpu, NULL, triggered);
+                bp = perf_event_create_kernel_counter(attr, cpu, NULL,
+                                                      triggered, context);
 
                 *pevent = bp;