perf: Collapse and fix event_function_call() users

There is one common bug left in all the event_function_call() users,
between loading ctx->task and getting to the remote_function(),
ctx->task can already have been changed.

Therefore we need to double check and retry if ctx->task != current.

Insert another trampoline specific to event_function_call() that
checks for this and further validates state. This also allows getting
rid of the active/inactive functions.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

include/linux/perf_event.h

@@ -1044,7 +1044,7 @@ extern void perf_swevent_put_recursion_context(int rctx);
 extern u64 perf_swevent_set_period(struct perf_event *event);
 extern void perf_event_enable(struct perf_event *event);
 extern void perf_event_disable(struct perf_event *event);
-extern int __perf_event_disable(void *info);
+extern void perf_event_disable_local(struct perf_event *event);
 extern void perf_event_task_tick(void);
 #else /* !CONFIG_PERF_EVENTS: */
 static inline void *

kernel/events/hw_breakpoint.c

@@ -444,7 +444,7 @@ int modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *att
 	 * current task.
 	 */
 	if (irqs_disabled() && bp->ctx && bp->ctx->task == current)
-		__perf_event_disable(bp);
+		perf_event_disable_local(bp);
 	else
 		perf_event_disable(bp);