TaiJuWu commented on code in PR #10776:
URL: https://github.com/apache/nuttx/pull/10776#discussion_r1359878907
##########
sched/semaphore/spinlock.c:
##########
@@ -446,4 +446,225 @@ void spin_clrbit(FAR volatile cpu_set_t *set, unsigned
int cpu,
}
#endif
+#ifdef CONFIG_RW_SPINLOCK
+
+/****************************************************************************
+ * Name: read_lock
+ *
+ * Description:
+ * If this task does not already hold the spinlock, then loop until the
+ * spinlock is successfully locked.
+ *
+ * This implementation is non-reentrant and set a bit of lock.
+ *
+ * The priority of reader is higher than writter if a reader hold the
+ * lock, a new reader can get its lock but writer can't get this lock.
+ *
+ * Input Parameters:
+ * lock - A reference to the spinlock object to lock.
+ *
+ * Returned Value:
+ * None. When the function returns, the spinlock was successfully locked
+ * by this CPU.
+ *
+ * Assumptions:
+ * Not running at the interrupt level.
+ *
+ ****************************************************************************/
+
+void read_lock(FAR volatile rwlock_t *lock)
+{
+ rwlock_t old;
+
+ while (true)
+ {
+ old = atomic_load(lock);
+
+ if (old >= RW_SP_UNLOCKED &&
+ atomic_compare_exchange_strong(lock, &old, old + 1))
+ {
+ break;
+ }
+ else if (old < 0)
+ {
+ SP_DSB();
+ SP_WFE();
+ }
+ }
+
+ SP_DMB();
+}
+
+/****************************************************************************
+ * Name: read_trylock
+ *
+ * Description:
+ * If this task does not already hold the spinlock, then try to get the
+ * lock.
+ *
+ * This implementation is non-reentrant and set a bit of lock.
+ *
+ * The priority of reader is higher than writter if a reader hold the
+ * lock, a new reader can get its lock but writer can't get this lock.
+ *
+ * Input Parameters:
+ * lock - A reference to the spinlock object to lock.
+ *
+ * Returned Value:
+ * false - Failure, the spinlock was already locked
+ * true - Success, the spinlock was successfully locked
+ *
+ * Assumptions:
+ * Not running at the interrupt level.
+ *
+ ****************************************************************************/
+
+bool read_trylock(FAR volatile rwlock_t *lock)
+{
+ rwlock_t old = atomic_load(lock);
+
+ if (old >= RW_SP_UNLOCKED &&
+ atomic_compare_exchange_strong(lock, &old, old + 1))
+ {
+ SP_DMB();
+ return true;
+ }
+
+ return false;
+}
+
+/****************************************************************************
+ * Name: read_unlock
+ *
+ * Description:
+ * Release a bit on a non-reentrant spinlock.
+ *
+ * Input Parameters:
+ * lock - A reference to the spinlock object to unlock.
+ *
+ * Returned Value:
+ * None.
+ *
+ * Assumptions:
+ * Not running at the interrupt level.
+ *
+ ****************************************************************************/
+
+void read_unlock(FAR volatile rwlock_t *lock)
+{
+ DEBUGASSERT(atomic_load(lock) >= RW_SP_READ_LOCKED);
+
+ SP_DMB();
+ atomic_fetch_add(lock, -1);
+ SP_DSB();
+ SP_SEV();
+}
+
+/****************************************************************************
+ * Name: write_lock
+ *
+ * Description:
+ * If this task does not already hold the spinlock, then loop until the
+ * spinlock is successfully locked.
+ *
+ * This implementation is non-reentrant and set all bit on lock to avoid
+ * readers and writers.
+ *
+ * The priority of reader is higher than writter if a reader hold the
+ * lock, a new reader can get its lock but writer can't get this lock.
+ *
+ * Input Parameters:
+ * lock - A reference to the spinlock object to lock.
+ *
+ * Returned Value:
+ * None. When the function returns, the spinlock was successfully locked
+ * by this CPU.
+ *
+ * Assumptions:
+ * Not running at the interrupt level.
+ *
+ ****************************************************************************/
+
+void write_lock(FAR volatile rwlock_t *lock)
+{
+ rwlock_t zero = RW_SP_UNLOCKED;
+
+ while (!atomic_compare_exchange_strong(lock, &zero, RW_SP_WRITE_LOCKED))
+ {
+ SP_DSB();
+ SP_WFE();
+ }
+
+ SP_DMB();
+}
+
+/****************************************************************************
+ * Name: write_trylock
+ *
+ * Description:
+ * If this task does not already hold the spinlock, then loop until the
+ * spinlock is successfully locked.
+ *
+ * This implementation is non-reentrant and set all bit on lock to avoid
+ * readers and writers.
+ *
+ * The priority of reader is higher than writter if a reader hold the
+ * lock, a new reader can get its lock but writer can't get this lock.
+ *
+ * Input Parameters:
+ * lock - A reference to the spinlock object to lock.
+ *
+ * Returned Value:
+ * false - Failure, the spinlock was already locked
+ * true - Success, the spinlock was successfully locked
+ *
+ * Assumptions:
+ * Not running at the interrupt level.
+ *
+ ****************************************************************************/
+
+bool write_trylock(FAR volatile rwlock_t *lock)
+{
+ rwlock_t zero = RW_SP_UNLOCKED;
+
+ if (!atomic_compare_exchange_strong(lock, &zero, RW_SP_WRITE_LOCKED))
+ {
+ SP_DSB();
Review Comment:
I do't have any special reason.
The logical also can be modified to success case.
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