hw_breakpoint: Simplify *register_wide_hw_breakpoint()

1. register_wide_hw_breakpoint() can use unregister_ if failure,
   no need to duplicate the code.

2. "struct perf_event **pevent" adds the unnecesary lever of
   indirection and complication, use per_cpu(*cpu_events, cpu).

Reported-by: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/20130620155018.GA6347@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 11 insertions, 23 deletions

diff --git a/kernel/events/hw_breakpoint.c b/kernel/events/hw_breakpoint.c
index 9c71445328af..38418f786f36 100644
--- a/kernel/events/hw_breakpoint.c
+++ b/kernel/events/hw_breakpoint.c
@@ -497,8 +497,8 @@ register_wide_hw_breakpoint(struct perf_event_attr *attr,
                             perf_overflow_handler_t triggered,
                             void *context)
 {
-        struct perf_event * __percpu *cpu_events, **pevent, *bp;
-        long err;
+        struct perf_event * __percpu *cpu_events, *bp;
+        long err = 0;
         int cpu;
 
         cpu_events = alloc_percpu(typeof(*cpu_events));
@@ -507,31 +507,21 @@ 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, context);
-
-                *pevent = bp;
-
                 if (IS_ERR(bp)) {
                         err = PTR_ERR(bp);
-                        goto fail;
+                        break;
                 }
-        }
-        put_online_cpus();
-
-        return cpu_events;
 
-fail:
-        for_each_online_cpu(cpu) {
-                pevent = per_cpu_ptr(cpu_events, cpu);
-                if (IS_ERR(*pevent))
-                        break;
-                unregister_hw_breakpoint(*pevent);
+                per_cpu(*cpu_events, cpu) = bp;
         }
         put_online_cpus();
 
-        free_percpu(cpu_events);
+        if (likely(!err))
+                return cpu_events;
+
+        unregister_wide_hw_breakpoint(cpu_events);
         return (void __percpu __force *)ERR_PTR(err);
 }
 EXPORT_SYMBOL_GPL(register_wide_hw_breakpoint);
@@ -543,12 +533,10 @@ EXPORT_SYMBOL_GPL(register_wide_hw_breakpoint);
 void unregister_wide_hw_breakpoint(struct perf_event * __percpu *cpu_events)
 {
         int cpu;
-        struct perf_event **pevent;
 
-        for_each_possible_cpu(cpu) {
-                pevent = per_cpu_ptr(cpu_events, cpu);
-                unregister_hw_breakpoint(*pevent);
-        }
+        for_each_possible_cpu(cpu)
+                unregister_hw_breakpoint(per_cpu(*cpu_events, cpu));
+
         free_percpu(cpu_events);
 }
 EXPORT_SYMBOL_GPL(unregister_wide_hw_breakpoint);