From 487dab18f28a36982059c823103993123876778e Mon Sep 17 00:00:00 2001
From: braam <braam>
Date: Sun, 23 Jun 2002 19:12:57 +0000
Subject: [PATCH] - add reentrant locks

---
 lustre/include/linux/lustre_lib.h | 14 ++++++
 lustre/ldlm/Makefile.am           | 11 ++++-
 lustre/lib/l_lock.c               | 96 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 120 insertions(+), 1 deletion(-)
 create mode 100644 lustre/lib/l_lock.c

diff --git a/lustre/include/linux/lustre_lib.h b/lustre/include/linux/lustre_lib.h
index 3367c1d..8f5c5ac 100644
--- a/lustre/include/linux/lustre_lib.h
+++ b/lustre/include/linux/lustre_lib.h
@@ -32,9 +32,23 @@
 #endif
 
 #include <linux/portals_lib.h>
+#include <asm/semaphore.h>
 #include <linux/lustre_idl.h>
 
 #ifdef __KERNEL__
+/* l_lock.c */
+struct lustre_lock { 
+        int l_depth;
+        struct task_struct *l_owner;
+        struct semaphore l_sem;
+        spinlock_t l_spin;
+};
+
+void l_lock_init(struct lustre_lock *);
+void l_lock(struct lustre_lock *);
+void l_unlock(struct lustre_lock *);
+
+
 /* page.c */
 inline void lustre_put_page(struct page *page);
 struct page *lustre_get_page_read(struct inode *dir, unsigned long index);
diff --git a/lustre/ldlm/Makefile.am b/lustre/ldlm/Makefile.am
index da6256a..66b9203 100644
--- a/lustre/ldlm/Makefile.am
+++ b/lustre/ldlm/Makefile.am
@@ -8,8 +8,17 @@ MODULE = ldlm
 modulefs_DATA = ldlm.o
 EXTRA_PROGRAMS = ldlm
 
-ldlm_SOURCES = ldlm_lock.c ldlm_resource.c ldlm_test.c ldlm_lockd.c \
+l_lock.c: 
+	test -e l_lock.c || ln -sf $(top_srcdir)/lib/l_lock.c
+
+LINX=l_lock.c
+
+ldlm_SOURCES = l_lock.c ldlm_lock.c ldlm_resource.c ldlm_test.c ldlm_lockd.c \
 ldlm_extent.c ldlm_request.c
 
+dist-hook:
+	list='$(LINX)'; for f in $$list; do rm -f $(distdir)/$$f; done
+
+
 include $(top_srcdir)/Rules
 
diff --git a/lustre/lib/l_lock.c b/lustre/lib/l_lock.c
new file mode 100644
index 0000000..ca253a2
--- /dev/null
+++ b/lustre/lib/l_lock.c
@@ -0,0 +1,96 @@
+/* -*- mode: c; c-basic-offset: 8; indent-tabs-mode: nil; -*-
+ * vim:expandtab:shiftwidth=8:tabstop=8:
+ *
+ * Copyright (C) 2001, 2002 Cluster File Systems, Inc.
+ *
+ *   This file is part of Lustre, http://www.sf.net/projects/lustre/
+ *
+ *   Lustre is free software; you can redistribute it and/or
+ *   modify it under the terms of version 2 of the GNU General Public
+ *   License as published by the Free Software Foundation.
+ *
+ *   Lustre is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with Lustre; if not, write to the Free Software
+ *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ */
+
+
+
+#include <linux/config.h>
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/string.h>
+#include <linux/stat.h>
+#include <linux/errno.h>
+#include <linux/locks.h>
+#include <linux/unistd.h>
+#include <linux/version.h>
+
+#include <asm/system.h>
+#include <asm/uaccess.h>
+
+#include <linux/fs.h>
+#include <linux/stat.h>
+#include <asm/uaccess.h>
+#include <asm/segment.h>
+#include <linux/mm.h>
+#include <linux/pagemap.h>
+#include <linux/smp_lock.h>
+
+#define DEBUG_SUBSYSTEM S_LDLM
+
+#include <linux/obd_class.h>
+#include <linux/lustre_lib.h>
+
+/* invariants:
+ - only the owner of the lock changes l_owner/l_depth
+ - before changing or checking the variables a spin lock is taken
+*/
+
+void l_lock_init(struct lustre_lock *lock)
+{
+        sema_init(&lock->l_sem, 1);
+        spin_lock_init(&lock->l_spin);
+}
+
+void l_lock(struct lustre_lock *lock)
+{
+        int owner;
+        spin_lock(&lock->l_spin);
+        if (lock->l_owner == current) { 
+                owner = 1;
+        }
+        spin_unlock(&lock->l_spin);
+        if (owner)
+                 ++lock->l_depth;
+        else { 
+                down(&lock->l_sem);
+                spin_lock(&lock->l_spin);
+                lock->l_owner = current;
+                lock->l_depth = 0;
+                spin_unlock(&lock->l_spin);
+        }
+}
+
+void l_unlock(struct lustre_lock *lock)
+{
+        if (lock->l_owner != current)
+                LBUG();
+        if (lock->l_depth < 0)
+                LBUG();
+
+        spin_lock(&lock->l_spin); 
+        if (--lock->l_depth < 0) { 
+                lock->l_owner = NULL;
+                spin_unlock(&lock->l_spin);
+                up(&lock->l_sem);
+                return ;
+        }
+        spin_unlock(&lock->l_spin);
+}
-- 
1.8.3.1