perf/core: Generalize event->group_flags

Currently, PERF_GROUP_SOFTWARE is used in the group_flags field of a
group's leader to indicate that is_software_event(event) is true for all
events in a group. This is the only usage of event->group_flags.

This pattern of setting a group level flags when all events in the group
share a property is useful for the flag introduced in the next patch and
for future CQM/CMT flags. So this patches generalizes group_flags to work
as an aggregate of event level flags.

PERF_GROUP_SOFTWARE denotes an inmutable event's property. All other flags
that I intend to add are also determinable at event initialization.
To better convey the above, this patch renames event's group_flags to
group_caps and PERF_GROUP_SOFTWARE to PERF_EV_CAP_SOFTWARE.

Individual event flags are stored in the new event->event_caps. Since the
cap flags do not change after event initialization, there is no need to
serialize event_caps. This new field is used when events are added to a
context, similarly to how PERF_GROUP_SOFTWARE and is_software_event()
worked.

Lastly, for consistency, updates is_software_event() to rely in event_cap
instead of the context index.

Signed-off-by: David Carrillo-Cisneros <davidcc@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Turner <pjt@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vegard Nossum <vegard.nossum@gmail.com>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Link: http://lkml.kernel.org/r/1471467307-61171-3-git-send-email-davidcc@google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 8 insertions, 8 deletions

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 849919c2f3d7..8c42a5ae9030 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -1475,8 +1475,7 @@ list_add_event(struct perf_event *event, struct perf_event_context *ctx)
 	if (event->group_leader == event) {
 		struct list_head *list;
 
-		if (is_software_event(event))
-			event->group_flags |= PERF_GROUP_SOFTWARE;
+		event->group_caps = event->event_caps;
 
 		list = ctx_group_list(event, ctx);
 		list_add_tail(&event->group_entry, list);
@@ -1630,9 +1629,7 @@ static void perf_group_attach(struct perf_event *event)
 
 	WARN_ON_ONCE(group_leader->ctx != event->ctx);
 
-	if (group_leader->group_flags & PERF_GROUP_SOFTWARE &&
-			!is_software_event(event))
-		group_leader->group_flags &= ~PERF_GROUP_SOFTWARE;
+	group_leader->group_caps &= event->event_caps;
 
 	list_add_tail(&event->group_entry, &group_leader->sibling_list);
 	group_leader->nr_siblings++;
@@ -1723,7 +1720,7 @@ static void perf_group_detach(struct perf_event *event)
 		sibling->group_leader = sibling;
 
 		/* Inherit group flags from the previous leader */
-		sibling->group_flags = event->group_flags;
+		sibling->group_caps = event->group_caps;
 
 		WARN_ON_ONCE(sibling->ctx != event->ctx);
 	}
@@ -2149,7 +2146,7 @@ static int group_can_go_on(struct perf_event *event,
 	/*
 	 * Groups consisting entirely of software events can always go on.
 	 */
-	if (event->group_flags & PERF_GROUP_SOFTWARE)
+	if (event->group_caps & PERF_EV_CAP_SOFTWARE)
 		return 1;
 	/*
 	 * If an exclusive group is already on, no other hardware
@@ -9490,6 +9487,9 @@ SYSCALL_DEFINE5(perf_event_open,
 			goto err_alloc;
 	}
 
+	if (pmu->task_ctx_nr == perf_sw_context)
+		event->event_caps |= PERF_EV_CAP_SOFTWARE;
+
 	if (group_leader &&
 	    (is_software_event(event) != is_software_event(group_leader))) {
 		if (is_software_event(event)) {
@@ -9503,7 +9503,7 @@ SYSCALL_DEFINE5(perf_event_open,
 			 */
 			pmu = group_leader->pmu;
 		} else if (is_software_event(group_leader) &&
-			   (group_leader->group_flags & PERF_GROUP_SOFTWARE)) {
+			   (group_leader->group_caps & PERF_EV_CAP_SOFTWARE)) {
 			/*
 			 * In case the group is a pure software group, and we
 			 * try to add a hardware event, move the whole group to