[dpdk-dev] [PATCH] eal/rwlocks: Try read/write and relock write to read locks added.

[Leonid Myravjev <asm@asm.pp.ru>]

From: Leonid Myravjev <myravjev@amicon.ru>

Signed-off-by: Leonid Myravjev <myravjev@amicon.ru>
---
 lib/librte_eal/common/include/generic/rte_rwlock.h | 61 ++++++++++++++++++++++
 1 file changed, 61 insertions(+)

diff --git a/lib/librte_eal/common/include/generic/rte_rwlock.h b/lib/librte_eal/common/include/generic/rte_rwlock.h
index 899e9bc43..11212e2b8 100644
--- a/lib/librte_eal/common/include/generic/rte_rwlock.h
+++ b/lib/librte_eal/common/include/generic/rte_rwlock.h
@@ -76,6 +76,30 @@ rte_rwlock_read_lock(rte_rwlock_t *rwl)
 }
 
 /**
+ * Try take lock a read lock.
+ *
+ * @param rwl
+ *   A pointer to a rwlock structure.
+ * @return
+ *   1 if the lock is successfully taken; 0 otherwise.
+ */
+static inline int
+rte_rwlock_read_trylock(rte_rwlock_t *rwl)
+{
+	int32_t x;
+	int success = 0;
+
+	x = rwl->cnt;
+	/* write lock is held */
+	if (x < 0)
+		return 0;
+	success = rte_atomic32_cmpset((volatile uint32_t *)&rwl->cnt, x, x + 1);
+	if (success == 0)
+		return 0;
+	return 1;
+}
+
+/**
  * Release a read lock.
  *
  * @param rwl
@@ -110,6 +134,29 @@ rte_rwlock_write_lock(rte_rwlock_t *rwl)
 					      0, -1);
 	}
 }
+/**
+ * Try take a write lock.
+ *
+ * @param rwl
+ *   A pointer to a rwlock structure.
+ * @return
+ *   1 if the lock is successfully taken; 0 otherwise.
+ */
+static inline int
+rte_rwlock_write_trylock(rte_rwlock_t *rwl)
+{
+	int32_t x;
+	int success = 0;
+
+	x = rwl->cnt;
+	/* a lock is held */
+	if (x != 0)
+		return 0;
+	success = rte_atomic32_cmpset((volatile uint32_t *)&rwl->cnt, 0, -1);
+	if (success == 0)
+		return 0;
+	return 1;
+}
 
 /**
  * Release a write lock.
@@ -124,6 +171,20 @@ rte_rwlock_write_unlock(rte_rwlock_t *rwl)
 }
 
 /**
+ * Relock write lock to read
+ *
+ * @param rwl
+ *   A pointer to a rwlock structure.
+ */
+static inline void
+rte_rwlock_write_relock_read(rte_rwlock_t *rwl)
+{
+	rte_atomic32_add((rte_atomic32_t *)(intptr_t)&rwl->cnt, 2);
+}
+
+
+
+/**
  * Try to execute critical section in a hardware memory transaction, if it
  * fails or not available take a read lock
  *
-- 
2.13.0