[PATCH] mutex subsystem, core

mutex implementation, core files: just the basic subsystem, no users of it.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@infradead.org>

1 files changed, 119 insertions, 0 deletions

diff --git a/include/linux/mutex.h b/include/linux/mutex.h
new file mode 100644
index 000000000000..9bce0fee68d4
--- /dev/null
+++ b/include/linux/mutex.h
@@ -0,0 +1,119 @@
+/*
+ * Mutexes: blocking mutual exclusion locks
+ *
+ * started by Ingo Molnar:
+ *
+ *  Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
+ *
+ * This file contains the main data structure and API definitions.
+ */
+#ifndef __LINUX_MUTEX_H
+#define __LINUX_MUTEX_H
+
+#include <linux/list.h>
+#include <linux/spinlock_types.h>
+
+#include <asm/atomic.h>
+
+/*
+ * Simple, straightforward mutexes with strict semantics:
+ *
+ * - only one task can hold the mutex at a time
+ * - only the owner can unlock the mutex
+ * - multiple unlocks are not permitted
+ * - recursive locking is not permitted
+ * - a mutex object must be initialized via the API
+ * - a mutex object must not be initialized via memset or copying
+ * - task may not exit with mutex held
+ * - memory areas where held locks reside must not be freed
+ * - held mutexes must not be reinitialized
+ * - mutexes may not be used in irq contexts
+ *
+ * These semantics are fully enforced when DEBUG_MUTEXES is
+ * enabled. Furthermore, besides enforcing the above rules, the mutex
+ * debugging code also implements a number of additional features
+ * that make lock debugging easier and faster:
+ *
+ * - uses symbolic names of mutexes, whenever they are printed in debug output
+ * - point-of-acquire tracking, symbolic lookup of function names
+ * - list of all locks held in the system, printout of them
+ * - owner tracking
+ * - detects self-recursing locks and prints out all relevant info
+ * - detects multi-task circular deadlocks and prints out all affected
+ *   locks and tasks (and only those tasks)
+ */
+struct mutex {
+        /* 1: unlocked, 0: locked, negative: locked, possible waiters */
+        atomic_t                count;
+        spinlock_t              wait_lock;
+        struct list_head        wait_list;
+#ifdef CONFIG_DEBUG_MUTEXES
+        struct thread_info      *owner;
+        struct list_head        held_list;
+        unsigned long           acquire_ip;
+        const char              *name;
+        void                    *magic;
+#endif
+};
+
+/*
+ * This is the control structure for tasks blocked on mutex,
+ * which resides on the blocked task's kernel stack:
+ */
+struct mutex_waiter {
+        struct list_head        list;
+        struct task_struct      *task;
+#ifdef CONFIG_DEBUG_MUTEXES
+        struct mutex            *lock;
+        void                    *magic;
+#endif
+};
+
+#ifdef CONFIG_DEBUG_MUTEXES
+# include <linux/mutex-debug.h>
+#else
+# define __DEBUG_MUTEX_INITIALIZER(lockname)
+# define mutex_init(mutex)                      __mutex_init(mutex, NULL)
+# define mutex_destroy(mutex)                           do { } while (0)
+# define mutex_debug_show_all_locks()                   do { } while (0)
+# define mutex_debug_show_held_locks(p)                 do { } while (0)
+# define mutex_debug_check_no_locks_held(task)          do { } while (0)
+# define mutex_debug_check_no_locks_freed(from, to)     do { } while (0)
+#endif
+
+#define __MUTEX_INITIALIZER(lockname) \
+                { .count = ATOMIC_INIT(1) \
+                , .wait_lock = SPIN_LOCK_UNLOCKED \
+                , .wait_list = LIST_HEAD_INIT(lockname.wait_list) \
+                __DEBUG_MUTEX_INITIALIZER(lockname) }
+
+#define DEFINE_MUTEX(mutexname) \
+        struct mutex mutexname = __MUTEX_INITIALIZER(mutexname)
+
+extern void fastcall __mutex_init(struct mutex *lock, const char *name);
+
+/***
+ * mutex_is_locked - is the mutex locked
+ * @lock: the mutex to be queried
+ *
+ * Returns 1 if the mutex is locked, 0 if unlocked.
+ */
+static inline int fastcall mutex_is_locked(struct mutex *lock)
+{
+        return atomic_read(&lock->count) != 1;
+}
+
+/*
+ * See kernel/mutex.c for detailed documentation of these APIs.
+ * Also see Documentation/mutex-design.txt.
+ */
+extern void fastcall mutex_lock(struct mutex *lock);
+extern int fastcall mutex_lock_interruptible(struct mutex *lock);
+/*
+ * NOTE: mutex_trylock() follows the spin_trylock() convention,
+ *       not the down_trylock() convention!
+ */
+extern int fastcall mutex_trylock(struct mutex *lock);
+extern void fastcall mutex_unlock(struct mutex *lock);
+
+#endif