perf_counter: Fix COMM and MMAP events for cpu wide counters

Commit a63eaf34ae6 ("perf_counter: Dynamically allocate tasks'
perf_counter_context struct") broke COMM and MMAP notification for
cpu wide counters by dropping out early if there was no task context,
thereby also not iterating the cpu context.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/perf_counter.c

@@ -2443,9 +2443,9 @@ static void perf_counter_comm_event(struct perf_comm_event *comm_event)
 
 	cpuctx = &get_cpu_var(perf_cpu_context);
 	perf_counter_comm_ctx(&cpuctx->ctx, comm_event);
+	if (cpuctx->task_ctx)
+		perf_counter_comm_ctx(cpuctx->task_ctx, comm_event);
 	put_cpu_var(perf_cpu_context);
-
-	perf_counter_comm_ctx(current->perf_counter_ctxp, comm_event);
 }
 
 void perf_counter_comm(struct task_struct *task)
@@ -2454,8 +2454,6 @@ void perf_counter_comm(struct task_struct *task)
 
 	if (!atomic_read(&nr_comm_tracking))
 		return;
-	if (!current->perf_counter_ctxp)
-		return;
 
 	comm_event = (struct perf_comm_event){
 		.task	= task,
@@ -2570,10 +2568,10 @@ got_name:
 
 	cpuctx = &get_cpu_var(perf_cpu_context);
 	perf_counter_mmap_ctx(&cpuctx->ctx, mmap_event);
+	if (cpuctx->task_ctx)
+		perf_counter_mmap_ctx(cpuctx->task_ctx, mmap_event);
 	put_cpu_var(perf_cpu_context);
 
-	perf_counter_mmap_ctx(current->perf_counter_ctxp, mmap_event);
-
 	kfree(buf);
 }
 
@@ -2584,8 +2582,6 @@ void perf_counter_mmap(unsigned long addr, unsigned long len,
 
 	if (!atomic_read(&nr_mmap_tracking))
 		return;
-	if (!current->perf_counter_ctxp)
-		return;
 
 	mmap_event = (struct perf_mmap_event){
 		.file   = file,