[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.
  *