[PATCH v3 25/46] perf/x86/intel/cmt: add monr->flags and CMT_MONR_ZOMBIE

[David Carrillo-Cisneros <davidcc@google.com>]

Add a new enumeration to store monr's internal state information.
This new monr->flags contrasts with monr->uflag that stores user
provided flags.

The first flags is CMT_MONR_ZOMBIE, used to signal that the monr is no
longer valid, yet, must be kept around until its released by its last
user. This is useful when a monr is attached to a cgroup that is destroyed
but there are still events that reference that cgroup.

Signed-off-by: David Carrillo-Cisneros <davidcc@google.com>
---
 arch/x86/events/intel/cmt.c | 17 +++++++++++++++--
 arch/x86/events/intel/cmt.h |  9 +++++++++
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/arch/x86/events/intel/cmt.c b/arch/x86/events/intel/cmt.c
index 7545deb..830ce29 100644
--- a/arch/x86/events/intel/cmt.c
+++ b/arch/x86/events/intel/cmt.c
@@ -423,7 +423,12 @@ static void monr_dealloc(struct monr *monr)
 {
 	u16 p, nr_pkgs = topology_max_packages();
 
-	if (WARN_ON_ONCE(monr->nr_has_user) ||
+	/*
+	 * Only can dealloc monrs zombie monrs with all pmonrs in Off state
+	 * and not attached to the monr hierarchy.
+	 */
+	if (WARN_ON_ONCE(!(monr->flags & CMT_MONR_ZOMBIE)) ||
+	    WARN_ON_ONCE(monr->nr_has_user) ||
 	    WARN_ON_ONCE(monr->nr_nolazy_rmid) ||
 	    WARN_ON_ONCE(monr->mon_cgrp) ||
 	    WARN_ON_ONCE(monr->mon_events))
@@ -1178,12 +1183,20 @@ static int monr_hrchy_attach_event(struct perf_event *event)
 
 static void monr_destroy(struct monr *monr)
 {
+	if (monr->flags & CMT_MONR_ZOMBIE)
+		goto zombie;
+
 #ifdef CONFIG_CGROUP_PERF
 	if (monr->mon_cgrp)
 		__css_stop_monitoring(&monr->mon_cgrp->css);
 #endif
 	monr_hrchy_remove_leaf(monr);
-	monr_dealloc(monr);
+
+	monr->flags = CMT_MONR_ZOMBIE;
+
+zombie:
+	if (!monr_has_user(monr))
+		monr_dealloc(monr);
 }
 
 /**
diff --git a/arch/x86/events/intel/cmt.h b/arch/x86/events/intel/cmt.h
index dc52641..1e40e6b 100644
--- a/arch/x86/events/intel/cmt.h
+++ b/arch/x86/events/intel/cmt.h
@@ -240,6 +240,13 @@ struct pkg_data {
 };
 
 /**
+ * enum monr_flags - internal monr's flags.
+ */
+enum monr_flags {
+	CMT_MONR_ZOMBIE = BIT(0), /* monr has been terminated. */
+};
+
+/**
  * enum cmt_user_flags - user set flags for monr and pmonrs.
  */
 enum cmt_user_flags {
@@ -259,6 +266,7 @@ enum cmt_user_flags {
  * @parent:		Parent in monr hierarchy.
  * @children:		List of children in monr hierarchy.
  * @parent_entry:	Entry in parent's children list.
+ * @flags:		monr_flags.
  * @nr_has_user:	nr of CMT_UF_HAS_USER set in events in mon_events.
  * @nr_nolazy_user:	nr of CMT_UF_NOLAZY_RMID set in events in mon_events.
  * @uflags:		monr level cmt_user_flags, or'ed with pkg_uflags.
@@ -281,6 +289,7 @@ struct monr {
 	struct list_head		children;
 	struct list_head		parent_entry;
 
+	enum monr_flags			flags;
 	int				nr_has_user;
 	int				nr_nolazy_rmid;
 	enum cmt_user_flags		uflags;
-- 
2.8.0.rc3.226.g39d4020