On 9/24/21 9:09 AM, Chandan Babu R wrote:

From: Dave Chinner <redacted>

These provide the kernel spinlock_t interface, but are *not*
spinlocks. Spinlocks cannot be used by general purpose userspace
processes due to the fact they cannot control task preemption and
scheduling reliability. Hence these are implemented as a
pthread_mutex_t, similar to the way the kernel RT build implements
spinlock_t as a kernel mutex.

Because the current libxfs spinlock "implementation" just makes
spinlocks go away, we have to also add initialisation to spinlocks
that libxfs uses that are missing from the userspace implementation.

Signed-off-by: Dave Chinner <redacted>
[chandan.babu@oracle.com: Initialize inode log item spin lock]
Signed-off-by: Chandan Babu R <redacted>

...

+/*
+ * This implements kernel compatible spinlock exclusion semantics. These,
+ * however, are not spinlocks, as spinlocks cannot be reliably implemented in
+ * userspace without using realtime scheduling task contexts. Hence this
+ * interface is implemented with pthread mutexes and so can block, but this is
+ * no different to the kernel RT build which replaces spinlocks with mutexes.
+ * Hence we know it works.
+ */
+
+typedef pthread_mutex_t	spinlock_t;
+
+#define spin_lock_init(l)	pthread_mutex_init(l, NULL)
+#define spin_lock(l)           pthread_mutex_lock(l)
+#define spin_trylock(l)        (pthread_mutex_trylock(l) != EBUSY)
+#define spin_unlock(l)         pthread_mutex_unlock(l)

some whitespace mess here but I'll just clean that up.

Reviewed-by: Eric Sandeen <redacted>