base: genlock: Remove genlock_release_lock and associated ioctl

Allowing a lock to be asynchronously released while a handle
was still active turned out to be too dangerous to use in a
multi-threaded environment and it served no pratical
purpose anyway.  Handles now hold an attached lock until they
are destroyed.

CRs-fixed: 333141
Change-Id: Ic0dedbad8050ff01927ddb165c65a939bf297c10
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>

Documentation/genlock.txt

@@ -82,15 +82,13 @@ descriptor.
 Release a handle.
 
 * struct genlock * genlock_create_lock(struct genlock_handle *)
-Create a new lock and attach it to the handle.
+Create a new lock and attach it to the handle.  Once a lock is attached to a
+handle it stays attached until the handle is destroyed.
 
 * struct genlock * genlock_attach_lock(struct genlock_handle *handle, int fd)
 Given a valid file descriptor, get the lock associated with it and attach it to
 the handle.
 
-* void genlock_release_lock(struct genlock_handle *)
-Release a lock attached to a handle.
-
 * int genlock_lock(struct genlock_handle *, int op, int flags, u32 timeout)
 Lock or unlock the lock attached to the handle. A zero timeout value will
 be treated just like if the GENOCK_NOBLOCK flag is passed; if the lock
@@ -155,7 +153,4 @@ passed in genlock_lock.timeout. Returns 0 when the lock has been released,
 -EINVAL if a zero timeout is passed, or -ETIMEDOUT if the timeout expires.
 
 * GENLOCK_IOC_RELEASE
-Use this to release an existing lock. This is useful if you wish to attach a
+This ioctl has been deprecated.  Do not use.
-different lock to the same handle. You do not need to call this under normal
-circumstances; when the handle is closed the reference to the lock is released.
-No data is passed from the user for this ioctl.

drivers/base/genlock.c

@@ -496,12 +496,7 @@ done:
 	return ret;
 }
 
-/**
+static void genlock_release_lock(struct genlock_handle *handle)
- * genlock_release_lock - Release a lock attached to a handle
- * @handle - Pointer to the handle holding the lock
- */
-
-void genlock_release_lock(struct genlock_handle *handle)
 {
 	unsigned long flags;
 
@@ -522,7 +517,6 @@ void genlock_release_lock(struct genlock_handle *handle)
 	handle->lock = NULL;
 	handle->active = 0;
 }
-EXPORT_SYMBOL(genlock_release_lock);
 
 /*
  * Release function called when all references to a handle are released
@@ -671,8 +665,13 @@ static long genlock_dev_ioctl(struct file *filep, unsigned int cmd,
 		return genlock_wait(handle, param.timeout);
 	}
 	case GENLOCK_IOC_RELEASE: {
-		genlock_release_lock(handle);
+		/*
-		return 0;
+		 * Return error - this ioctl has been deprecated.
+		 * Locks should only be released when the handle is
+		 * destroyed
+		 */
+		GENLOCK_LOG_ERR("Deprecated RELEASE ioctl called\n");
+		return -EINVAL;
 	}
 	default:
 		GENLOCK_LOG_ERR("Invalid ioctl\n");

include/linux/genlock.h

@@ -12,7 +12,7 @@ void genlock_put_handle(struct genlock_handle *handle);
 struct genlock *genlock_create_lock(struct genlock_handle *);
 struct genlock *genlock_attach_lock(struct genlock_handle *, int fd);
 int genlock_wait(struct genlock_handle *handle, u32 timeout);
-void genlock_release_lock(struct genlock_handle *);
+/* genlock_release_lock was deprecated */
 int genlock_lock(struct genlock_handle *handle, int op, int flags,
 	u32 timeout);
 #endif
@@ -39,6 +39,8 @@ struct genlock_lock {
 	struct genlock_lock)
 #define GENLOCK_IOC_LOCK _IOW(GENLOCK_IOC_MAGIC, 3, \
 	struct genlock_lock)
+
+/* Deprecated */
 #define GENLOCK_IOC_RELEASE _IO(GENLOCK_IOC_MAGIC, 4)
 #define GENLOCK_IOC_WAIT _IOW(GENLOCK_IOC_MAGIC, 5, \
 	struct genlock_lock)