hw-breakpoints: Use overflow handler instead of the event callback

struct perf_event::event callback was called when a breakpoint
triggers. But this is a rather opaque callback, pretty
tied-only to the breakpoint API and not really integrated into perf
as it triggers even when we don't overflow.

We prefer to use overflow_handler() as it fits into the perf events
rules, being called only when we overflow.

Reported-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: "K. Prasad" <prasad@linux.vnet.ibm.com>

2 files changed, 18 insertions, 20 deletions

diff --git a/include/linux/hw_breakpoint.h b/include/linux/hw_breakpoint.h
index d33096e0dbd4..4d14a384a01e 100644
--- a/include/linux/hw_breakpoint.h
+++ b/include/linux/hw_breakpoint.h
@@ -20,19 +20,16 @@ enum {
 
 #ifdef CONFIG_HAVE_HW_BREAKPOINT
 
-/* As it's for in-kernel or ptrace use, we want it to be pinned */
-#define DEFINE_BREAKPOINT_ATTR(name)    \
-struct perf_event_attr name = {         \
-        .type = PERF_TYPE_BREAKPOINT,   \
-        .size = sizeof(name),           \
-        .pinned = 1,                    \
-};
-
 static inline void hw_breakpoint_init(struct perf_event_attr *attr)
 {
         attr->type = PERF_TYPE_BREAKPOINT;
         attr->size = sizeof(*attr);
+        /*
+         * As it's for in-kernel or ptrace use, we want it to be pinned
+         * and to call its callback every hits.
+         */
         attr->pinned = 1;
+        attr->sample_period = 1;
 }
 
 static inline unsigned long hw_breakpoint_addr(struct perf_event *bp)
@@ -52,7 +49,7 @@ static inline int hw_breakpoint_len(struct perf_event *bp)
 
 extern struct perf_event *
 register_user_hw_breakpoint(struct perf_event_attr *attr,
-                            perf_callback_t triggered,
+                            perf_overflow_handler_t triggered,
                             struct task_struct *tsk);
 
 /* FIXME: only change from the attr, and don't unregister */
@@ -64,12 +61,12 @@ modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *attr);
  */
 extern struct perf_event *
 register_wide_hw_breakpoint_cpu(struct perf_event_attr *attr,
-                                perf_callback_t triggered,
+                                perf_overflow_handler_t triggered,
                                 int cpu);
 
 extern struct perf_event **
 register_wide_hw_breakpoint(struct perf_event_attr *attr,
-                            perf_callback_t triggered);
+                            perf_overflow_handler_t triggered);
 
 extern int register_perf_hw_breakpoint(struct perf_event *bp);
 extern int __register_perf_hw_breakpoint(struct perf_event *bp);
@@ -90,18 +87,18 @@ static inline struct arch_hw_breakpoint *counter_arch_bp(struct perf_event *bp)
 
 static inline struct perf_event *
 register_user_hw_breakpoint(struct perf_event_attr *attr,
-                            perf_callback_t triggered,
+                            perf_overflow_handler_t triggered,
                             struct task_struct *tsk)    { return NULL; }
 static inline struct perf_event *
 modify_user_hw_breakpoint(struct perf_event *bp,
                           struct perf_event_attr *attr) { return NULL; }
 static inline struct perf_event *
 register_wide_hw_breakpoint_cpu(struct perf_event_attr *attr,
-                                perf_callback_t triggered,
+                                perf_overflow_handler_t  triggered,
                                 int cpu)                { return NULL; }
 static inline struct perf_event **
 register_wide_hw_breakpoint(struct perf_event_attr *attr,
-                            perf_callback_t triggered)  { return NULL; }
+                            perf_overflow_handler_t triggered)  { return NULL; }
 static inline int
 register_perf_hw_breakpoint(struct perf_event *bp)      { return -ENOSYS; }
 static inline int
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 84bd28a0ffab..d2f2667430da 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -565,10 +565,13 @@ struct perf_pending_entry {
         void (*func)(struct perf_pending_entry *);
 };
 
-typedef void (*perf_callback_t)(struct perf_event *, void *);
-
 struct perf_sample_data;
 
+typedef void (*perf_callback_t)(struct perf_event *, void *);
+typedef void (*perf_overflow_handler_t)(struct perf_event *, int,
+                                        struct perf_sample_data *,
+                                        struct pt_regs *regs);
+
 /**
  * struct perf_event - performance event kernel representation:
  */
@@ -660,9 +663,7 @@ struct perf_event {
         struct pid_namespace            *ns;
         u64                             id;
 
-        void (*overflow_handler)(struct perf_event *event,
-                        int nmi, struct perf_sample_data *data,
-                        struct pt_regs *regs);
+        perf_overflow_handler_t         overflow_handler;
 
 #ifdef CONFIG_EVENT_PROFILE
         struct event_filter             *filter;
@@ -779,7 +780,7 @@ extern struct perf_event *
 perf_event_create_kernel_counter(struct perf_event_attr *attr,
                                 int cpu,
                                 pid_t pid,
-                                perf_callback_t callback);
+                                perf_overflow_handler_t callback);
 extern u64 perf_event_read_value(struct perf_event *event,
                                  u64 *enabled, u64 *running);