[lttng-dev] [PATCH v2 06/12] urcu-wait: Fix wait state load/store

[Olivier Dion]

The state of a wait node must be accessed atomically. Also, the action
of busy loading until the teardown state is seen must follow a
CMM_ACQUIRE semantic while storing the teardown must follow a
CMM_RELEASE semantic.

Change-Id: I9cd9cf4cd9ab2081551d7f33c0b1c23c3cf3942f
Co-authored-by: Mathieu Desnoyers <mathieu.desnoyers at efficios.com>
Signed-off-by: Olivier Dion <odion at efficios.com>
---
 src/urcu-wait.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/urcu-wait.h b/src/urcu-wait.h
index ef5f7ed..4667a13 100644
--- a/src/urcu-wait.h
+++ b/src/urcu-wait.h
@@ -135,7 +135,7 @@ void urcu_adaptative_wake_up(struct urcu_wait_node *wait)
 			urcu_die(errno);
 	}
 	/* Allow teardown of struct urcu_wait memory. */
-	uatomic_or(&wait->state, URCU_WAIT_TEARDOWN);
+	uatomic_or_mo(&wait->state, URCU_WAIT_TEARDOWN, CMM_RELEASE);
 }
 
 /*
@@ -193,7 +193,7 @@ skip_futex_wait:
 			break;
 		caa_cpu_relax();
 	}
-	while (!(uatomic_read(&wait->state) & URCU_WAIT_TEARDOWN))
+	while (!(uatomic_load(&wait->state, CMM_ACQUIRE) & URCU_WAIT_TEARDOWN))
 		poll(NULL, 0, 10);
 	urcu_posix_assert(uatomic_read(&wait->state) & URCU_WAIT_TEARDOWN);
 }
@@ -209,7 +209,7 @@ void urcu_wake_all_waiters(struct urcu_waiters *waiters)
 			caa_container_of(iter, struct urcu_wait_node, node);
 
 		/* Don't wake already running threads */
-		if (wait_node->state & URCU_WAIT_RUNNING)
+		if (uatomic_load(&wait_node->state, CMM_RELAXED) & URCU_WAIT_RUNNING)
 			continue;
 		urcu_adaptative_wake_up(wait_node);
 	}
-- 
2.40.1