[lttng-dev] [PATCH] QSBR: Use xor operation to replace add operation when changing rcu_gp.ctr value

[yaowenbin]

It is enough to have three values of rcu_gp.ctr, 00 for INACTIVE,
01 or 11 for ACTIVE. So it is possible to replace add operation
with xor operation when changing rcu_gp.ctr value.

Signed-off-by: yaowenbin <yaowenbin1 at huawei.com>
---
 src/urcu-qsbr.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/urcu-qsbr.c b/src/urcu-qsbr.c
index 3709412..46135f9 100644
--- a/src/urcu-qsbr.c
+++ b/src/urcu-qsbr.c
@@ -391,7 +391,7 @@ void urcu_qsbr_synchronize_rcu(void)
 		goto out;

 	/* Increment current G.P. */
-	CMM_STORE_SHARED(urcu_qsbr_gp.ctr, urcu_qsbr_gp.ctr + URCU_QSBR_GP_CTR);
+	CMM_STORE_SHARED(urcu_qsbr_gp.ctr, urcu_qsbr_gp.ctr ^ URCU_QSBR_GP_CTR);

 	/*
 	 * Must commit urcu_qsbr_gp.ctr update to memory before waiting for
-- 
2.27.0