[PATCH v16 40/42] dept: introduce event_site() to disable event tracking if it's recoverable

[Byungchul Park]

With multi event sites for a single wait, dept allows to skip tracking
an event that is recoverable by other recover paths.

Introduce an API, event_site(), to skip tracking the event in the case.

Signed-off-by: Byungchul Park <byungchul at sk.com>
---
 include/linux/dept.h     | 30 ++++++++++++++++++++++++++++++
 include/linux/sched.h    |  6 ++++++
 kernel/dependency/dept.c | 20 ++++++++++++++++++++
 3 files changed, 56 insertions(+)

diff --git a/include/linux/dept.h b/include/linux/dept.h
index 25fdd324614a..0ac13129f308 100644
--- a/include/linux/dept.h
+++ b/include/linux/dept.h
@@ -487,6 +487,31 @@ extern void dept_task_exit(struct task_struct *t);
 extern void dept_free_range(void *start, unsigned int sz);
 extern void dept_mark_event_site_used(void *start, void *end);
 
+extern void disable_event_track(void);
+extern void enable_event_track(void);
+
+#define event_site(es, evt_func, ...)					\
+do {									\
+	unsigned long _flags;						\
+	bool _disable;							\
+									\
+	local_irq_save(_flags);						\
+	dept_event_site_used(es);					\
+	/*								\
+	 * If !list_empty(&(es)->dept_head), the event site can be	\
+	 * recovered by others.  Do not track event dependency if so.	\
+	 */								\
+	_disable = !list_empty(&(es)->dep_head);			\
+	if (_disable)							\
+		disable_event_track();					\
+									\
+	evt_func(__VA_ARGS__);						\
+									\
+	if (_disable)							\
+		enable_event_track();					\
+	local_irq_restore(_flags);					\
+} while (0)
+
 extern void dept_map_init(struct dept_map *m, struct dept_key *k, int sub_u, const char *n);
 extern void dept_map_reinit(struct dept_map *m, struct dept_key *k, int sub_u, const char *n);
 extern void dept_ext_wgen_init(struct dept_ext_wgen *ewg);
@@ -550,6 +575,11 @@ struct dept_event_site { };
 #define dept_task_exit(t)				do { } while (0)
 #define dept_free_range(s, sz)				do { } while (0)
 #define dept_mark_event_site_used(s, e)			do { } while (0)
+#define event_site(es, evt_func, ...)					\
+do {									\
+	(void)(es);							\
+	evt_func(__VA_ARGS__);						\
+} while (0)
 
 #define dept_map_init(m, k, su, n)			do { (void)(n); (void)(k); } while (0)
 #define dept_map_reinit(m, k, su, n)			do { (void)(n); (void)(k); } while (0)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 43927e61921b..44a77b7116b7 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -873,6 +873,11 @@ struct dept_task {
 	 */
 	int				missing_ecxt;
 
+	/*
+	 * not to track events
+	 */
+	int				disable_event_track_cnt;
+
 	/*
 	 * for tracking IRQ-enable state
 	 */
@@ -910,6 +915,7 @@ struct dept_task {
 	.stage_wait_stack = NULL,				\
 	.stage_lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED,\
 	.missing_ecxt = 0,					\
+	.disable_event_track_cnt = 0,				\
 	.hardirqs_enabled = false,				\
 	.softirqs_enabled = false,				\
 	.task_exit = false,					\
diff --git a/kernel/dependency/dept.c b/kernel/dependency/dept.c
index baa60bd0fb93..c65bb0c6dad2 100644
--- a/kernel/dependency/dept.c
+++ b/kernel/dependency/dept.c
@@ -2573,6 +2573,23 @@ static void __dept_wait(struct dept_map *m, unsigned long w_f,
 	}
 }
 
+void disable_event_track(void)
+{
+	dept_task()->disable_event_track_cnt++;
+}
+EXPORT_SYMBOL_GPL(disable_event_track);
+
+void enable_event_track(void)
+{
+	dept_task()->disable_event_track_cnt--;
+}
+EXPORT_SYMBOL_GPL(enable_event_track);
+
+static bool event_track_disabled(void)
+{
+	return !!dept_task()->disable_event_track_cnt;
+}
+
 /*
  * Called between dept_enter() and dept_exit().
  */
@@ -2585,6 +2602,9 @@ static void __dept_event(struct dept_map *m, struct dept_map *real_m,
 	struct dept_key *k;
 	int e;
 
+	if (event_track_disabled())
+		return;
+
 	e = find_first_bit(&e_f, DEPT_MAX_SUBCLASSES_EVT);
 
 	if (DEPT_WARN_ON(e >= DEPT_MAX_SUBCLASSES_EVT))
-- 
2.17.1