1 files changed, 264 insertions, 0 deletions

diff --git a/lib/kernel_lock.c b/lib/kernel_lock.c
new file mode 100644
index 000000000000..99b0ae3d51dd
--- /dev/null
+++ b/lib/kernel_lock.c
@@ -0,0 +1,264 @@
+/*
+ * lib/kernel_lock.c
+ *
+ * This is the traditional BKL - big kernel lock. Largely
+ * relegated to obsolescense, but used by various less
+ * important (or lazy) subsystems.
+ */
+#include <linux/smp_lock.h>
+#include <linux/module.h>
+#include <linux/kallsyms.h>
+
+#if defined(CONFIG_PREEMPT) && defined(__smp_processor_id) && \
+                defined(CONFIG_DEBUG_PREEMPT)
+
+/*
+ * Debugging check.
+ */
+unsigned int smp_processor_id(void)
+{
+        unsigned long preempt_count = preempt_count();
+        int this_cpu = __smp_processor_id();
+        cpumask_t this_mask;
+
+        if (likely(preempt_count))
+                goto out;
+
+        if (irqs_disabled())
+                goto out;
+
+        /*
+         * Kernel threads bound to a single CPU can safely use
+         * smp_processor_id():
+         */
+        this_mask = cpumask_of_cpu(this_cpu);
+
+        if (cpus_equal(current->cpus_allowed, this_mask))
+                goto out;
+
+        /*
+         * It is valid to assume CPU-locality during early bootup:
+         */
+        if (system_state != SYSTEM_RUNNING)
+                goto out;
+
+        /*
+         * Avoid recursion:
+         */
+        preempt_disable();
+
+        if (!printk_ratelimit())
+                goto out_enable;
+
+        printk(KERN_ERR "BUG: using smp_processor_id() in preemptible [%08x] code: %s/%d\n", preempt_count(), current->comm, current->pid);
+        print_symbol("caller is %s\n", (long)__builtin_return_address(0));
+        dump_stack();
+
+out_enable:
+        preempt_enable_no_resched();
+out:
+        return this_cpu;
+}
+
+EXPORT_SYMBOL(smp_processor_id);
+
+#endif /* PREEMPT && __smp_processor_id && DEBUG_PREEMPT */
+
+#ifdef CONFIG_PREEMPT_BKL
+/*
+ * The 'big kernel semaphore'
+ *
+ * This mutex is taken and released recursively by lock_kernel()
+ * and unlock_kernel().  It is transparently dropped and reaquired
+ * over schedule().  It is used to protect legacy code that hasn't
+ * been migrated to a proper locking design yet.
+ *
+ * Note: code locked by this semaphore will only be serialized against
+ * other code using the same locking facility. The code guarantees that
+ * the task remains on the same CPU.
+ *
+ * Don't use in new code.
+ */
+static DECLARE_MUTEX(kernel_sem);
+
+/*
+ * Re-acquire the kernel semaphore.
+ *
+ * This function is called with preemption off.
+ *
+ * We are executing in schedule() so the code must be extremely careful
+ * about recursion, both due to the down() and due to the enabling of
+ * preemption. schedule() will re-check the preemption flag after
+ * reacquiring the semaphore.
+ */
+int __lockfunc __reacquire_kernel_lock(void)
+{
+        struct task_struct *task = current;
+        int saved_lock_depth = task->lock_depth;
+
+        BUG_ON(saved_lock_depth < 0);
+
+        task->lock_depth = -1;
+        preempt_enable_no_resched();
+
+        down(&kernel_sem);
+
+        preempt_disable();
+        task->lock_depth = saved_lock_depth;
+
+        return 0;
+}
+
+void __lockfunc __release_kernel_lock(void)
+{
+        up(&kernel_sem);
+}
+
+/*
+ * Getting the big kernel semaphore.
+ */
+void __lockfunc lock_kernel(void)
+{
+        struct task_struct *task = current;
+        int depth = task->lock_depth + 1;
+
+        if (likely(!depth))
+                /*
+                 * No recursion worries - we set up lock_depth _after_
+                 */
+                down(&kernel_sem);
+
+        task->lock_depth = depth;
+}
+
+void __lockfunc unlock_kernel(void)
+{
+        struct task_struct *task = current;
+
+        BUG_ON(task->lock_depth < 0);
+
+        if (likely(--task->lock_depth < 0))
+                up(&kernel_sem);
+}
+
+#else
+
+/*
+ * The 'big kernel lock'
+ *
+ * This spinlock is taken and released recursively by lock_kernel()
+ * and unlock_kernel().  It is transparently dropped and reaquired
+ * over schedule().  It is used to protect legacy code that hasn't
+ * been migrated to a proper locking design yet.
+ *
+ * Don't use in new code.
+ */
+static  __cacheline_aligned_in_smp DEFINE_SPINLOCK(kernel_flag);
+
+
+/*
+ * Acquire/release the underlying lock from the scheduler.
+ *
+ * This is called with preemption disabled, and should
+ * return an error value if it cannot get the lock and
+ * TIF_NEED_RESCHED gets set.
+ *
+ * If it successfully gets the lock, it should increment
+ * the preemption count like any spinlock does.
+ *
+ * (This works on UP too - _raw_spin_trylock will never
+ * return false in that case)
+ */
+int __lockfunc __reacquire_kernel_lock(void)
+{
+        while (!_raw_spin_trylock(&kernel_flag)) {
+                if (test_thread_flag(TIF_NEED_RESCHED))
+                        return -EAGAIN;
+                cpu_relax();
+        }
+        preempt_disable();
+        return 0;
+}
+
+void __lockfunc __release_kernel_lock(void)
+{
+        _raw_spin_unlock(&kernel_flag);
+        preempt_enable_no_resched();
+}
+
+/*
+ * These are the BKL spinlocks - we try to be polite about preemption. 
+ * If SMP is not on (ie UP preemption), this all goes away because the
+ * _raw_spin_trylock() will always succeed.
+ */
+#ifdef CONFIG_PREEMPT
+static inline void __lock_kernel(void)
+{
+        preempt_disable();
+        if (unlikely(!_raw_spin_trylock(&kernel_flag))) {
+                /*
+                 * If preemption was disabled even before this
+                 * was called, there's nothing we can be polite
+                 * about - just spin.
+                 */
+                if (preempt_count() > 1) {
+                        _raw_spin_lock(&kernel_flag);
+                        return;
+                }
+
+                /*
+                 * Otherwise, let's wait for the kernel lock
+                 * with preemption enabled..
+                 */
+                do {
+                        preempt_enable();
+                        while (spin_is_locked(&kernel_flag))
+                                cpu_relax();
+                        preempt_disable();
+                } while (!_raw_spin_trylock(&kernel_flag));
+        }
+}
+
+#else
+
+/*
+ * Non-preemption case - just get the spinlock
+ */
+static inline void __lock_kernel(void)
+{
+        _raw_spin_lock(&kernel_flag);
+}
+#endif
+
+static inline void __unlock_kernel(void)
+{
+        _raw_spin_unlock(&kernel_flag);
+        preempt_enable();
+}
+
+/*
+ * Getting the big kernel lock.
+ *
+ * This cannot happen asynchronously, so we only need to
+ * worry about other CPU's.
+ */
+void __lockfunc lock_kernel(void)
+{
+        int depth = current->lock_depth+1;
+        if (likely(!depth))
+                __lock_kernel();
+        current->lock_depth = depth;
+}
+
+void __lockfunc unlock_kernel(void)
+{
+        BUG_ON(current->lock_depth < 0);
+        if (likely(--current->lock_depth < 0))
+                __unlock_kernel();
+}
+
+#endif
+
+EXPORT_SYMBOL(lock_kernel);
+EXPORT_SYMBOL(unlock_kernel);
+