[PATCH] pi-futex: rt mutex tester

RT-mutex tester: scriptable tester for rt mutexes, which allows userspace
scripting of mutex unit-tests (and dynamic tests as well), using the actual
rt-mutex implementation of the kernel.

[akpm@osdl.org: fixlet]
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

4 files changed, 461 insertions, 1 deletions

diff --git a/kernel/Makefile b/kernel/Makefile
index f9c92d34cde5..82fb182f6f61 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -18,6 +18,7 @@ obj-$(CONFIG_FUTEX) += futex_compat.o
 endif
 obj-$(CONFIG_RT_MUTEXES) += rtmutex.o
 obj-$(CONFIG_DEBUG_RT_MUTEXES) += rtmutex-debug.o
+obj-$(CONFIG_RT_MUTEX_TESTER) += rtmutex-tester.o
 obj-$(CONFIG_GENERIC_ISA_DMA) += dma.o
 obj-$(CONFIG_SMP) += cpu.o spinlock.o
 obj-$(CONFIG_DEBUG_SPINLOCK) += spinlock.o
diff --git a/kernel/rtmutex-tester.c b/kernel/rtmutex-tester.c
new file mode 100644
index 000000000000..fe211ba3a5b5
--- /dev/null
+++ b/kernel/rtmutex-tester.c
@@ -0,0 +1,436 @@
+/*
+ * RT-Mutex-tester: scriptable tester for rt mutexes
+ *
+ * started by Thomas Gleixner:
+ *
+ *  Copyright (C) 2006, Timesys Corp., Thomas Gleixner <tglx@timesys.com>
+ *
+ */
+#include <linux/config.h>
+#include <linux/kthread.h>
+#include <linux/module.h>
+#include <linux/sched.h>
+#include <linux/smp_lock.h>
+#include <linux/spinlock.h>
+#include <linux/sysdev.h>
+#include <linux/timer.h>
+
+#include "rtmutex.h"
+
+#define MAX_RT_TEST_THREADS	8
+#define MAX_RT_TEST_MUTEXES	8
+
+static spinlock_t rttest_lock;
+static atomic_t rttest_event;
+
+struct test_thread_data {
+	int			opcode;
+	int			opdata;
+	int			mutexes[MAX_RT_TEST_MUTEXES];
+	int			bkl;
+	int			event;
+	struct sys_device	sysdev;
+};
+
+static struct test_thread_data thread_data[MAX_RT_TEST_THREADS];
+static task_t *threads[MAX_RT_TEST_THREADS];
+static struct rt_mutex mutexes[MAX_RT_TEST_MUTEXES];
+
+enum test_opcodes {
+	RTTEST_NOP = 0,
+	RTTEST_SCHEDOT,		/* 1 Sched other, data = nice */
+	RTTEST_SCHEDRT,		/* 2 Sched fifo, data = prio */
+	RTTEST_LOCK,		/* 3 Lock uninterruptible, data = lockindex */
+	RTTEST_LOCKNOWAIT,	/* 4 Lock uninterruptible no wait in wakeup, data = lockindex */
+	RTTEST_LOCKINT,		/* 5 Lock interruptible, data = lockindex */
+	RTTEST_LOCKINTNOWAIT,	/* 6 Lock interruptible no wait in wakeup, data = lockindex */
+	RTTEST_LOCKCONT,	/* 7 Continue locking after the wakeup delay */
+	RTTEST_UNLOCK,		/* 8 Unlock, data = lockindex */
+	RTTEST_LOCKBKL, 	/* 9 Lock BKL */
+	RTTEST_UNLOCKBKL,	/* 10 Unlock BKL */
+	RTTEST_SIGNAL,		/* 11 Signal other test thread, data = thread id */
+	RTTEST_RESETEVENT = 98,	/* 98 Reset event counter */
+	RTTEST_RESET = 99,	/* 99 Reset all pending operations */
+};
+
+static int handle_op(struct test_thread_data *td, int lockwakeup)
+{
+	struct sched_param schedpar;
+	int i, id, ret = -EINVAL;
+
+	switch(td->opcode) {
+
+	case RTTEST_NOP:
+		return 0;
+
+	case RTTEST_SCHEDOT:
+		schedpar.sched_priority = 0;
+		ret = sched_setscheduler(current, SCHED_NORMAL, &schedpar);
+		if (!ret)
+			set_user_nice(current, 0);
+		return ret;
+
+	case RTTEST_SCHEDRT:
+		schedpar.sched_priority = td->opdata;
+		return sched_setscheduler(current, SCHED_FIFO, &schedpar);
+
+	case RTTEST_LOCKCONT:
+		td->mutexes[td->opdata] = 1;
+		td->event = atomic_add_return(1, &rttest_event);
+		return 0;
+
+	case RTTEST_RESET:
+		for (i = 0; i < MAX_RT_TEST_MUTEXES; i++) {
+			if (td->mutexes[i] == 4) {
+				rt_mutex_unlock(&mutexes[i]);
+				td->mutexes[i] = 0;
+			}
+		}
+
+		if (!lockwakeup && td->bkl == 4) {
+			unlock_kernel();
+			td->bkl = 0;
+		}
+		return 0;
+
+	case RTTEST_RESETEVENT:
+		atomic_set(&rttest_event, 0);
+		return 0;
+
+	default:
+		if (lockwakeup)
+			return ret;
+	}
+
+	switch(td->opcode) {
+
+	case RTTEST_LOCK:
+	case RTTEST_LOCKNOWAIT:
+		id = td->opdata;
+		if (id < 0 || id >= MAX_RT_TEST_MUTEXES)
+			return ret;
+
+		td->mutexes[id] = 1;
+		td->event = atomic_add_return(1, &rttest_event);
+		rt_mutex_lock(&mutexes[id]);
+		td->event = atomic_add_return(1, &rttest_event);
+		td->mutexes[id] = 4;
+		return 0;
+
+	case RTTEST_LOCKINT:
+	case RTTEST_LOCKINTNOWAIT:
+		id = td->opdata;
+		if (id < 0 || id >= MAX_RT_TEST_MUTEXES)
+			return ret;
+
+		td->mutexes[id] = 1;
+		td->event = atomic_add_return(1, &rttest_event);
+		ret = rt_mutex_lock_interruptible(&mutexes[id], 0);
+		td->event = atomic_add_return(1, &rttest_event);
+		td->mutexes[id] = ret ? 0 : 4;
+		return ret ? -EINTR : 0;
+
+	case RTTEST_UNLOCK:
+		id = td->opdata;
+		if (id < 0 || id >= MAX_RT_TEST_MUTEXES || td->mutexes[id] != 4)
+			return ret;
+
+		td->event = atomic_add_return(1, &rttest_event);
+		rt_mutex_unlock(&mutexes[id]);
+		td->event = atomic_add_return(1, &rttest_event);
+		td->mutexes[id] = 0;
+		return 0;
+
+	case RTTEST_LOCKBKL:
+		if (td->bkl)
+			return 0;
+		td->bkl = 1;
+		lock_kernel();
+		td->bkl = 4;
+		return 0;
+
+	case RTTEST_UNLOCKBKL:
+		if (td->bkl != 4)
+			break;
+		unlock_kernel();
+		td->bkl = 0;
+		return 0;
+
+	default:
+		break;
+	}
+	return ret;
+}
+
+/*
+ * Schedule replacement for rtsem_down(). Only called for threads with
+ * PF_MUTEX_TESTER set.
+ *
+ * This allows us to have finegrained control over the event flow.
+ *
+ */
+void schedule_rt_mutex_test(struct rt_mutex *mutex)
+{
+	int tid, op, dat;
+	struct test_thread_data *td;
+
+	/* We have to lookup the task */
+	for (tid = 0; tid < MAX_RT_TEST_THREADS; tid++) {
+		if (threads[tid] == current)
+			break;
+	}
+
+	BUG_ON(tid == MAX_RT_TEST_THREADS);
+
+	td = &thread_data[tid];
+
+	op = td->opcode;
+	dat = td->opdata;
+
+	switch (op) {
+	case RTTEST_LOCK:
+	case RTTEST_LOCKINT:
+	case RTTEST_LOCKNOWAIT:
+	case RTTEST_LOCKINTNOWAIT:
+		if (mutex != &mutexes[dat])
+			break;
+
+		if (td->mutexes[dat] != 1)
+			break;
+
+		td->mutexes[dat] = 2;
+		td->event = atomic_add_return(1, &rttest_event);
+		break;
+
+	case RTTEST_LOCKBKL:
+	default:
+		break;
+	}
+
+	schedule();
+
+
+	switch (op) {
+	case RTTEST_LOCK:
+	case RTTEST_LOCKINT:
+		if (mutex != &mutexes[dat])
+			return;
+
+		if (td->mutexes[dat] != 2)
+			return;
+
+		td->mutexes[dat] = 3;
+		td->event = atomic_add_return(1, &rttest_event);
+		break;
+
+	case RTTEST_LOCKNOWAIT:
+	case RTTEST_LOCKINTNOWAIT:
+		if (mutex != &mutexes[dat])
+			return;
+
+		if (td->mutexes[dat] != 2)
+			return;
+
+		td->mutexes[dat] = 1;
+		td->event = atomic_add_return(1, &rttest_event);
+		return;
+
+	case RTTEST_LOCKBKL:
+		return;
+	default:
+		return;
+	}
+
+	td->opcode = 0;
+
+	for (;;) {
+		set_current_state(TASK_INTERRUPTIBLE);
+
+		if (td->opcode > 0) {
+			int ret;
+
+			set_current_state(TASK_RUNNING);
+			ret = handle_op(td, 1);
+			set_current_state(TASK_INTERRUPTIBLE);
+			if (td->opcode == RTTEST_LOCKCONT)
+				break;
+			td->opcode = ret;
+		}
+
+		/* Wait for the next command to be executed */
+		schedule();
+	}
+
+	/* Restore previous command and data */
+	td->opcode = op;
+	td->opdata = dat;
+}
+
+static int test_func(void *data)
+{
+	struct test_thread_data *td = data;
+	int ret;
+
+	current->flags |= PF_MUTEX_TESTER;
+	allow_signal(SIGHUP);
+
+	for(;;) {
+
+		set_current_state(TASK_INTERRUPTIBLE);
+
+		if (td->opcode > 0) {
+			set_current_state(TASK_RUNNING);
+			ret = handle_op(td, 0);
+			set_current_state(TASK_INTERRUPTIBLE);
+			td->opcode = ret;
+		}
+
+		/* Wait for the next command to be executed */
+		schedule();
+
+		if (signal_pending(current))
+			flush_signals(current);
+
+		if(kthread_should_stop())
+			break;
+	}
+	return 0;
+}
+
+/**
+ * sysfs_test_command - interface for test commands
+ * @dev:	thread reference
+ * @buf:	command for actual step
+ * @count:	length of buffer
+ *
+ * command syntax:
+ *
+ * opcode:data
+ */
+static ssize_t sysfs_test_command(struct sys_device *dev, const char *buf,
+				  size_t count)
+{
+	struct test_thread_data *td;
+	char cmdbuf[32];
+	int op, dat, tid;
+
+	td = container_of(dev, struct test_thread_data, sysdev);
+	tid = td->sysdev.id;
+
+	/* strings from sysfs write are not 0 terminated! */
+	if (count >= sizeof(cmdbuf))
+		return -EINVAL;
+
+	/* strip of \n: */
+	if (buf[count-1] == '\n')
+		count--;
+	if (count < 1)
+		return -EINVAL;
+
+	memcpy(cmdbuf, buf, count);
+	cmdbuf[count] = 0;
+
+	if (sscanf(cmdbuf, "%d:%d", &op, &dat) != 2)
+		return -EINVAL;
+
+	switch (op) {
+	case RTTEST_SIGNAL:
+		send_sig(SIGHUP, threads[tid], 0);
+		break;
+
+	default:
+		if (td->opcode > 0)
+			return -EBUSY;
+		td->opdata = dat;
+		td->opcode = op;
+		wake_up_process(threads[tid]);
+	}
+
+	return count;
+}
+
+/**
+ * sysfs_test_status - sysfs interface for rt tester
+ * @dev:	thread to query
+ * @buf:	char buffer to be filled with thread status info
+ */
+static ssize_t sysfs_test_status(struct sys_device *dev, char *buf)
+{
+	struct test_thread_data *td;
+	char *curr = buf;
+	task_t *tsk;
+	int i;
+
+	td = container_of(dev, struct test_thread_data, sysdev);
+	tsk = threads[td->sysdev.id];
+
+	spin_lock(&rttest_lock);
+
+	curr += sprintf(curr,
+		"O: %4d, E:%8d, S: 0x%08lx, P: %4d, N: %4d, B: %p, K: %d, M:",
+		td->opcode, td->event, tsk->state,
+			(MAX_RT_PRIO - 1) - tsk->prio,
+			(MAX_RT_PRIO - 1) - tsk->normal_prio,
+		tsk->pi_blocked_on, td->bkl);
+
+	for (i = MAX_RT_TEST_MUTEXES - 1; i >=0 ; i--)
+		curr += sprintf(curr, "%d", td->mutexes[i]);
+
+	spin_unlock(&rttest_lock);
+
+	curr += sprintf(curr, ", T: %p, R: %p\n", tsk,
+			mutexes[td->sysdev.id].owner);
+
+	return curr - buf;
+}
+
+static SYSDEV_ATTR(status, 0600, sysfs_test_status, NULL);
+static SYSDEV_ATTR(command, 0600, NULL, sysfs_test_command);
+
+static struct sysdev_class rttest_sysclass = {
+	set_kset_name("rttest"),
+};
+
+static int init_test_thread(int id)
+{
+	thread_data[id].sysdev.cls = &rttest_sysclass;
+	thread_data[id].sysdev.id = id;
+
+	threads[id] = kthread_run(test_func, &thread_data[id], "rt-test-%d", id);
+	if (IS_ERR(threads[id]))
+		return PTR_ERR(threads[id]);
+
+	return sysdev_register(&thread_data[id].sysdev);
+}
+
+static int init_rttest(void)
+{
+	int ret, i;
+
+	spin_lock_init(&rttest_lock);
+
+	for (i = 0; i < MAX_RT_TEST_MUTEXES; i++)
+		rt_mutex_init(&mutexes[i]);
+
+	ret = sysdev_class_register(&rttest_sysclass);
+	if (ret)
+		return ret;
+
+	for (i = 0; i < MAX_RT_TEST_THREADS; i++) {
+		ret = init_test_thread(i);
+		if (ret)
+			break;
+		ret = sysdev_create_file(&thread_data[i].sysdev, &attr_status);
+		if (ret)
+			break;
+		ret = sysdev_create_file(&thread_data[i].sysdev, &attr_command);
+		if (ret)
+			break;
+	}
+
+	printk("Initializing RT-Tester: %s\n", ret ? "Failed" : "OK" );
+
+	return ret;
+}
+
+device_initcall(init_rttest);
diff --git a/kernel/rtmutex.c b/kernel/rtmutex.c
index 937a474fae94..39c8ca0cf526 100644
--- a/kernel/rtmutex.c
+++ b/kernel/rtmutex.c
@@ -640,7 +640,8 @@ rt_mutex_slowlock(struct rt_mutex *lock, int state,
 
 		debug_rt_mutex_print_deadlock(&waiter);
 
-		schedule();
+		if (waiter.task)
+			schedule_rt_mutex(lock);
 
 		spin_lock(&lock->wait_lock);
 		set_current_state(state);
diff --git a/kernel/rtmutex_common.h b/kernel/rtmutex_common.h
index 50eed60eb085..e068024eeffc 100644
--- a/kernel/rtmutex_common.h
+++ b/kernel/rtmutex_common.h
@@ -15,6 +15,28 @@
 #include <linux/rtmutex.h>
 
 /*
+ * The rtmutex in kernel tester is independent of rtmutex debugging. We
+ * call schedule_rt_mutex_test() instead of schedule() for the tasks which
+ * belong to the tester. That way we can delay the wakeup path of those
+ * threads to provoke lock stealing and testing of  complex boosting scenarios.
+ */
+#ifdef CONFIG_RT_MUTEX_TESTER
+
+extern void schedule_rt_mutex_test(struct rt_mutex *lock);
+
+#define schedule_rt_mutex(_lock)				\
+  do {								\
+	if (!(current->flags & PF_MUTEX_TESTER))		\
+		schedule();					\
+	else							\
+		schedule_rt_mutex_test(_lock);			\
+  } while (0)
+
+#else
+# define schedule_rt_mutex(_lock)			schedule()
+#endif
+
+/*
  * This is the control structure for tasks blocked on a rt_mutex,
  * which is allocated on the kernel stack on of the blocked task.
  *