Changeset 2b4a9f26 in mainline for kernel/generic/include/synch/spinlock.h

Timestamp:

2010-05-20T19:30:18Z (14 years ago)

Author:

Martin Decky <martin@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

42bbbe2

Parents:

b10e6e31

Message:

Add interrupts-disabled spinlocks whose purpose is the semantic distinction between spinlocks acquired always with interrupts disabled and normal spinlocks.
The compile-time distinction is implemented by the means of the type system and basic code correctness properties can be checked by the debugging assertions during run-time (with CONFIG_DEBUG)

• Correct bracketing of top-level interrupts-disabled spinlocks
• Correctness of the use of nested interrupts-disabled spinlocks (interrupts must be actually disabled)
• Basic consistency of places where the interrupt level is restored

The API encapsulates the physical manipulation with the interrupt levels and also two common locking patterns

• Sequential unlocking of spinlock A before locking of spinlock B without restoring original interrupt level (irq_spinlock_pass())
• Hand-over-hand locking of two locks in the correct locking order, e.g. if A precedes B, then locking of B before unlocking A (irq_spinlock_exchange())

A new HAL function interrupts_disabled() should be implemented in each port to support the run-time checks of correctly disabled interrupts while locking nested interrupts-disabled spinlocks
(only in debug builds, not used in non-debug builds).

File:

• kernel/generic/include/synch/spinlock.h (modified) (9 diffs)

kernel/generic/include/synch/spinlock.h

@@ -49 +49 @@
 #ifdef CONFIG_DEBUG_SPINLOCK
         const char *name;
-#endif
+#endif /* CONFIG_DEBUG_SPINLOCK */
 } spinlock_t;
 
@@ -60 +60 @@
 
 /*
- * SPINLOCK_INITIALIZE is to be used for statically allocated spinlocks.
- * It declares and initializes the lock.
+ * SPINLOCK_INITIALIZE and SPINLOCK_STATIC_INITIALIZE are to be used
+ * for statically allocated spinlocks. They declare (either as global
+ * or static) symbol and initialize the lock.
  */
 #ifdef CONFIG_DEBUG_SPINLOCK
@@ -77 +78 @@
         }
 
-#define spinlock_lock(lock)     spinlock_lock_debug((lock))
-#define spinlock_unlock(lock)   spinlock_unlock_debug((lock))
-
-#else
+#define ASSERT_SPINLOCK(expr, lock) \
+        ASSERT_VERBOSE(expr, (lock)->name)
+
+#define spinlock_lock(lock)    spinlock_lock_debug((lock))
+#define spinlock_unlock(lock)  spinlock_unlock_debug((lock))
+
+#else /* CONFIG_DEBUG_SPINLOCK */
 
 #define SPINLOCK_INITIALIZE_NAME(lock_name, desc_name) \
@@ -92 +96 @@
         }
 
-#define spinlock_lock(lock)     atomic_lock_arch(&(lock)->val)
-#define spinlock_unlock(lock)   spinlock_unlock_nondebug((lock))
-
-#endif
+#define ASSERT_SPINLOCK(expr, lock) \
+        ASSERT(expr)
+
+#define spinlock_lock(lock)    atomic_lock_arch(&(lock)->val)
+#define spinlock_unlock(lock)  spinlock_unlock_nondebug((lock))
+
+#endif /* CONFIG_DEBUG_SPINLOCK */
 
 #define SPINLOCK_INITIALIZE(lock_name) \
@@ -103 +110 @@
         SPINLOCK_STATIC_INITIALIZE_NAME(lock_name, #lock_name)
 
-extern void spinlock_initialize(spinlock_t *lock, const char *name);
-extern int spinlock_trylock(spinlock_t *lock);
-extern void spinlock_lock_debug(spinlock_t *lock);
-extern void spinlock_unlock_debug(spinlock_t *lock);
+extern void spinlock_initialize(spinlock_t *, const char *);
+extern int spinlock_trylock(spinlock_t *);
+extern void spinlock_lock_debug(spinlock_t *);
+extern void spinlock_unlock_debug(spinlock_t *);
 
 /** Unlock spinlock
@@ -113 +120 @@
  *
  * @param sl Pointer to spinlock_t structure.
+ *
  */
 static inline void spinlock_unlock_nondebug(spinlock_t *lock)
@@ -141 +149 @@
         }
 
-#else
+#else /* CONFIG_DEBUG_SPINLOCK */
 
 #define DEADLOCK_PROBE_INIT(pname)
 #define DEADLOCK_PROBE(pname, value)
 
-#endif
+#endif /* CONFIG_DEBUG_SPINLOCK */
 
 #else /* CONFIG_SMP */
@@ -160 +168 @@
 #define SPINLOCK_INITIALIZE_NAME(name, desc_name)
 #define SPINLOCK_STATIC_INITIALIZE_NAME(name, desc_name)
+
+#define ASSERT_SPINLOCK(expr, lock)
 
 #define spinlock_initialize(lock, name)
@@ -170 +180 @@
 #define DEADLOCK_PROBE(pname, value)
 
+#endif /* CONFIG_SMP */
+
+typedef struct {
+        spinlock_t lock;  /**< Spinlock */
+        bool guard;       /**< Flag whether ipl is valid */
+        ipl_t ipl;        /**< Original interrupt level */
+} irq_spinlock_t;
+
+#define IRQ_SPINLOCK_DECLARE(lock_name)  irq_spinlock_t lock_name
+#define IRQ_SPINLOCK_EXTERN(lock_name)   extern irq_spinlock_t lock_name
+
+#define ASSERT_IRQ_SPINLOCK(expr, irq_lock) \
+        ASSERT_SPINLOCK(expr, &((irq_lock)->lock))
+
+/*
+ * IRQ_SPINLOCK_INITIALIZE and IRQ_SPINLOCK_STATIC_INITIALIZE are to be used
+ * for statically allocated interrupts-disabled spinlocks. They declare (either
+ * as global or static symbol) and initialize the lock.
+ */
+#ifdef CONFIG_DEBUG_SPINLOCK
+
+#define IRQ_SPINLOCK_INITIALIZE_NAME(lock_name, desc_name) \
+        irq_spinlock_t lock_name = { \
+                .lock = { \
+                        .name = desc_name, \
+                        .val = { 0 } \
+                }, \
+                .guard = false, \
+                .ipl = 0 \
+        }
+
+#define IRQ_SPINLOCK_STATIC_INITIALIZE_NAME(lock_name, desc_name) \
+        static irq_spinlock_t lock_name = { \
+                .lock = { \
+                        .name = desc_name, \
+                        .val = { 0 } \
+                }, \
+                .guard = false, \
+                .ipl = 0 \
+        }
+
+#else /* CONFIG_DEBUG_SPINLOCK */
+
+#define IRQ_SPINLOCK_INITIALIZE_NAME(lock_name, desc_name) \
+        irq_spinlock_t lock_name = { \
+                .lock = { \
+                        .val = { 0 } \
+                }, \
+                .guard = false, \
+                .ipl = 0 \
+        }
+
+#define IRQ_SPINLOCK_STATIC_INITIALIZE_NAME(lock_name, desc_name) \
+        static irq_spinlock_t lock_name = { \
+                .lock = { \
+                        .val = { 0 } \
+                }, \
+                .guard = false, \
+                .ipl = 0 \
+        }
+
+#endif /* CONFIG_DEBUG_SPINLOCK */
+
+#define IRQ_SPINLOCK_INITIALIZE(lock_name) \
+        IRQ_SPINLOCK_INITIALIZE_NAME(lock_name, #lock_name)
+
+#define IRQ_SPINLOCK_STATIC_INITIALIZE(lock_name) \
+        IRQ_SPINLOCK_STATIC_INITIALIZE_NAME(lock_name, #lock_name)
+
+/** Initialize interrupts-disabled spinlock
+ *
+ * @param lock IRQ spinlock to be initialized.
+ * @param name IRQ spinlock name.
+ *
+ */
+static inline void irq_spinlock_initialize(irq_spinlock_t *lock, const char *name)
+{
+        spinlock_initialize(&(lock->lock), name);
+        lock->guard = false;
+        lock->ipl = 0;
+}
+
+/** Lock interrupts-disabled spinlock
+ *
+ * Lock a spinlock which requires disabled interrupts.
+ *
+ * @param lock    IRQ spinlock to be locked.
+ * @param irq_dis If true, interrupts are actually disabled
+ *                prior locking the spinlock. If false, interrupts
+ *                are expected to be already disabled.
+ *
+ */
+static inline void irq_spinlock_lock(irq_spinlock_t *lock, bool irq_dis)
+{
+        if (irq_dis) {
+                ipl_t ipl = interrupts_disable();
+                spinlock_lock(&(lock->lock));
+                
+                lock->guard = true;
+                lock->ipl = ipl;
+        } else {
+                ASSERT_IRQ_SPINLOCK(interrupts_disabled(), lock);
+                
+                spinlock_lock(&(lock->lock));
+                ASSERT_IRQ_SPINLOCK(!lock->guard, lock);
+        }
+}
+
+/** Unlock interrupts-disabled spinlock
+ *
+ * Unlock a spinlock which requires disabled interrupts.
+ *
+ * @param lock    IRQ spinlock to be unlocked.
+ * @param irq_res If true, interrupts are restored to previously
+ *                saved interrupt level.
+ *
+ */
+static inline void irq_spinlock_unlock(irq_spinlock_t *lock, bool irq_res)
+{
+        ASSERT_IRQ_SPINLOCK(interrupts_disabled(), lock);
+        
+        if (irq_res) {
+                ASSERT_IRQ_SPINLOCK(lock->guard, lock);
+                
+                lock->guard = false;
+                ipl_t ipl = lock->ipl;
+                
+                spinlock_unlock(&(lock->lock));
+                interrupts_restore(ipl);
+        } else {
+                ASSERT_IRQ_SPINLOCK(!lock->guard, lock);
+                spinlock_unlock(&(lock->lock));
+        }
+}
+
+/** Lock interrupts-disabled spinlock
+ *
+ * Lock an interrupts-disabled spinlock conditionally. If the
+ * spinlock is not available at the moment, signal failure.
+ * Interrupts are expected to be already disabled.
+ *
+ * @param lock IRQ spinlock to be locked conditionally.
+ *
+ * @return Zero on failure, non-zero otherwise.
+ *
+ */
+static inline int irq_spinlock_trylock(irq_spinlock_t *lock)
+{
+        ASSERT_IRQ_SPINLOCK(interrupts_disabled(), lock);
+        int rc = spinlock_trylock(&(lock->lock));
+        
+        ASSERT_IRQ_SPINLOCK(!lock->guard, lock);
+        return rc;
+}
+
+/** Pass lock from one interrupts-disabled spinlock to another
+ *
+ * Pass lock from one IRQ spinlock to another IRQ spinlock
+ * without enabling interrupts during the process.
+ *
+ * The first IRQ spinlock is supposed to be locked.
+ *
+ * @param unlock IRQ spinlock to be unlocked.
+ * @param lock   IRQ spinlock to be locked.
+ *
+ */
+static inline void irq_spinlock_pass(irq_spinlock_t *unlock,
+    irq_spinlock_t *lock)
+{
+        ASSERT_IRQ_SPINLOCK(interrupts_disabled(), unlock);
+        
+        /* Pass guard from unlock to lock */
+        bool guard = unlock->guard;
+        ipl_t ipl = unlock->ipl;
+        unlock->guard = false;
+        
+        spinlock_unlock(&(unlock->lock));
+        spinlock_lock(&(lock->lock));
+        
+        ASSERT_IRQ_SPINLOCK(!lock->guard, lock);
+        
+        if (guard) {
+                lock->guard = true;
+                lock->ipl = ipl;
+        }
+}
+
+/** Hand-over-hand locking of interrupts-disabled spinlocks
+ *
+ * Implement hand-over-hand locking between two interrupts-disabled
+ * spinlocks without enabling interrupts during the process.
+ *
+ * The first IRQ spinlock is supposed to be locked.
+ *
+ * @param unlock IRQ spinlock to be unlocked.
+ * @param lock   IRQ spinlock to be locked.
+ *
+ */
+static inline void irq_spinlock_exchange(irq_spinlock_t *unlock,
+    irq_spinlock_t *lock)
+{
+        ASSERT_IRQ_SPINLOCK(interrupts_disabled(), unlock);
+        
+        spinlock_lock(&(lock->lock));
+        ASSERT_IRQ_SPINLOCK(!lock->guard, lock);
+        
+        /* Pass guard from unlock to lock */
+        if (unlock->guard) {
+                lock->guard = true;
+                lock->ipl = unlock->ipl;
+                unlock->guard = false;
+        }
+        
+        spinlock_unlock(&(unlock->lock));
+}
+
 #endif
 
-#endif
-
 /** @}
  */