From ffe9cbf9ca8eb9b6aa4f3d56c4d55cbaba15daa3 Mon Sep 17 00:00:00 2001
From: Samy Al Bahra <sbahra@backtrace.io>
Date: Sat, 8 Apr 2017 16:08:04 -0400
Subject: [PATCH] ck_epoch: ck_epoch_end returns true if forward progress has
 been made.

---
 include/ck_epoch.h                               | 9 +++++----
 regressions/ck_epoch/validate/ck_epoch_section.c | 3 ++-
 src/ck_epoch.c                                   | 9 ++++-----
 3 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/include/ck_epoch.h b/include/ck_epoch.h
index 17f69ea..453fa23 100644
--- a/include/ck_epoch.h
+++ b/include/ck_epoch.h
@@ -168,9 +168,10 @@ ck_epoch_begin(ck_epoch_record_t *record, ck_epoch_section_t *section)
 }
 
 /*
- * Marks the end of an epoch-protected section.
+ * Marks the end of an epoch-protected section. Returns true if no more
+ * sections exist for the caller.
  */
-CK_CC_FORCE_INLINE static void
+CK_CC_FORCE_INLINE static bool
 ck_epoch_end(ck_epoch_record_t *record, ck_epoch_section_t *section)
 {
 
@@ -178,9 +179,9 @@ ck_epoch_end(ck_epoch_record_t *record, ck_epoch_section_t *section)
 	ck_pr_store_uint(&record->active, record->active - 1);
 
 	if (section != NULL)
-		_ck_epoch_delref(record, section);
+		return _ck_epoch_delref(record, section);
 
-	return;
+	return record->active == 0;
 }
 
 /*
diff --git a/regressions/ck_epoch/validate/ck_epoch_section.c b/regressions/ck_epoch/validate/ck_epoch_section.c
index 769043b..7b76d1c 100644
--- a/regressions/ck_epoch/validate/ck_epoch_section.c
+++ b/regressions/ck_epoch/validate/ck_epoch_section.c
@@ -88,7 +88,8 @@ test_simple_read_section(void)
 	ck_epoch_begin(&record, &section);
 	ck_epoch_call(&record, &entry, cleanup);
 	assert(cleanup_calls == 0);
-	ck_epoch_end(&record, &section);
+	if (ck_epoch_end(&record, &section) == false)
+		ck_error("expected no more sections");
 	ck_epoch_barrier(&record);
 	assert(cleanup_calls == 1);
 
diff --git a/src/ck_epoch.c b/src/ck_epoch.c
index 66cbb0c..a3273b4 100644
--- a/src/ck_epoch.c
+++ b/src/ck_epoch.c
@@ -139,7 +139,7 @@ CK_STACK_CONTAINER(struct ck_epoch_entry, stack_entry,
 
 #define CK_EPOCH_SENSE_MASK	(CK_EPOCH_SENSE - 1)
 
-void
+bool
 _ck_epoch_delref(struct ck_epoch_record *record,
     struct ck_epoch_section *section)
 {
@@ -150,7 +150,7 @@ _ck_epoch_delref(struct ck_epoch_record *record,
 	current->count--;
 
 	if (current->count > 0)
-		return;
+		return false;
 
 	/*
 	 * If the current bucket no longer has any references, then
@@ -161,8 +161,7 @@ _ck_epoch_delref(struct ck_epoch_record *record,
 	 * If no other active bucket exists, then the record will go
 	 * inactive in order to allow for forward progress.
 	 */
-	other = &record->local.bucket[(i + 1) &
-	    CK_EPOCH_SENSE_MASK];
+	other = &record->local.bucket[(i + 1) & CK_EPOCH_SENSE_MASK];
 	if (other->count > 0 &&
 	    ((int)(current->epoch - other->epoch) < 0)) {
 		/*
@@ -172,7 +171,7 @@ _ck_epoch_delref(struct ck_epoch_record *record,
 		ck_pr_store_uint(&record->epoch, other->epoch);
 	}
 
-	return;
+	return true;
 }
 
 void