Remove unneeded initializer

[systemtap.git] / runtime / transport / ring_buffer.c

#include <linux/types.h>
#include <linux/ring_buffer.h>
#include <linux/wait.h>
#include <linux/poll.h>
#include <linux/cpumask.h>

static DEFINE_PER_CPU(local_t, _stp_cpu_disabled);

static inline void _stp_ring_buffer_disable_cpu(void)
{
        preempt_disable();
        local_inc(&__get_cpu_var(_stp_cpu_disabled));
}

static inline void _stp_ring_buffer_enable_cpu(void)
{
        local_dec(&__get_cpu_var(_stp_cpu_disabled));
        preempt_enable();
}

static inline int _stp_ring_buffer_cpu_disabled(void)
{
    return local_read(&__get_cpu_var(_stp_cpu_disabled));
}

#ifndef STP_RELAY_TIMER_INTERVAL
/* Wakeup timer interval in jiffies (default 10 ms) */
#define STP_RELAY_TIMER_INTERVAL                ((HZ + 99) / 100)
#endif

struct _stp_data_entry {
        size_t                  len;
        unsigned char           buf[];
};

/*
 * Trace iterator - used by printout routines who present trace
 * results to users and which routines might sleep, etc:
 */
struct _stp_iterator {
        int                     cpu_file;
        struct ring_buffer_iter *buffer_iter[NR_CPUS];
        int                     cpu;
        u64                     ts;
        atomic_t                nr_events;
};

/* In bulk mode, we need 1 'struct _stp_iterator' for each cpu.  In
 * 'normal' mode, we only need 1 'struct _stp_iterator' (since all
 * output is sent through 1 file). */
#ifdef STP_BULKMODE
#define NR_ITERS NR_CPUS
#else
#define NR_ITERS 1
#endif

struct _stp_relay_data_type {
        atomic_t /* enum _stp_transport_state */ transport_state;
        struct ring_buffer *rb;
        struct _stp_iterator iter[NR_ITERS];
        cpumask_var_t trace_reader_cpumask;
        struct timer_list timer;
        int overwrite_flag;
};
static struct _stp_relay_data_type _stp_relay_data;

/* _stp_poll_wait is a waitqueue for tasks blocked on
 * _stp_data_poll_trace() */
static DECLARE_WAIT_QUEUE_HEAD(_stp_poll_wait);

static void __stp_free_ring_buffer(void)
{
        free_cpumask_var(_stp_relay_data.trace_reader_cpumask);
        if (_stp_relay_data.rb)
                ring_buffer_free(_stp_relay_data.rb);
        _stp_relay_data.rb = NULL;
}

static int __stp_alloc_ring_buffer(void)
{
        int i;
        unsigned long buffer_size = _stp_bufsize;

        if (!alloc_cpumask_var(&_stp_relay_data.trace_reader_cpumask,
                               GFP_KERNEL))
                goto fail;
        cpumask_clear(_stp_relay_data.trace_reader_cpumask);

        if (buffer_size == 0) {
                dbug_trans(1, "using default buffer size...\n");
                buffer_size = _stp_nsubbufs * _stp_subbuf_size;
        }
        /* The number passed to ring_buffer_alloc() is per cpu.  Our
         * 'buffer_size' is a total number of bytes to allocate.  So,
         * we need to divide buffer_size by the number of cpus. */
        buffer_size /= num_online_cpus();
        dbug_trans(1, "%lu\n", buffer_size);
        _stp_relay_data.rb = ring_buffer_alloc(buffer_size, 0);
        if (!_stp_relay_data.rb)
                goto fail;

        dbug_trans(0, "size = %lu\n", ring_buffer_size(_stp_relay_data.rb));
        return 0;

fail:
        __stp_free_ring_buffer();
        return -ENOMEM;
}

static int _stp_data_open_trace(struct inode *inode, struct file *file)
{
        struct _stp_iterator *iter = inode->i_private;
#ifdef STP_BULKMODE
        int cpu_file = iter->cpu_file;
#endif

        /* We only allow for one reader per cpu */
        dbug_trans(1, "trace attach\n");
#ifdef STP_BULKMODE
        if (!cpumask_test_cpu(cpu_file, _stp_relay_data.trace_reader_cpumask))
                cpumask_set_cpu(cpu_file, _stp_relay_data.trace_reader_cpumask);
        else {
                dbug_trans(1, "returning EBUSY\n");
                return -EBUSY;
        }
#else
        if (!cpumask_empty(_stp_relay_data.trace_reader_cpumask)) {
                dbug_trans(1, "returning EBUSY\n");
                return -EBUSY;
        }
        cpumask_setall(_stp_relay_data.trace_reader_cpumask);
#endif
        file->private_data = inode->i_private;
        return 0;
}

static int _stp_data_release_trace(struct inode *inode, struct file *file)
{
        struct _stp_iterator *iter = inode->i_private;

        dbug_trans(1, "trace detach\n");
#ifdef STP_BULKMODE
        cpumask_clear_cpu(iter->cpu_file, _stp_relay_data.trace_reader_cpumask);
#else
        cpumask_clear(_stp_relay_data.trace_reader_cpumask);
#endif
        return 0;
}

size_t
_stp_event_to_user(struct ring_buffer_event *event, char __user *ubuf,
                   size_t cnt)
{
        int ret;
        struct _stp_data_entry *entry;

        dbug_trans(1, "event(%p), ubuf(%p), cnt(%lu)\n", event, ubuf, cnt);
        if (event == NULL || ubuf == NULL) {
                dbug_trans(1, "returning -EFAULT(1)\n");
                return -EFAULT;
        }

        entry = ring_buffer_event_data(event);
        if (entry == NULL) {
                dbug_trans(1, "returning -EFAULT(2)\n");
                return -EFAULT;
        }

        /* We don't do partial entries - just fail. */
        if (entry->len > cnt) {
                dbug_trans(1, "returning -EBUSY\n");
                return -EBUSY;
        }

#if defined(DEBUG_TRANS) && (DEBUG_TRANS >= 2)
        {
                char *last = entry->buf + (entry->len - 5);
                dbug_trans2("copying %.5s...%.5s\n", entry->buf, last);
        }
#endif

        if (cnt > entry->len)
                cnt = entry->len;
        ret = copy_to_user(ubuf, entry->buf, cnt);
        if (ret) {
                dbug_trans(1, "returning -EFAULT(3)\n");
                return -EFAULT;
        }

        return cnt;
}

static int _stp_ring_buffer_empty_cpu(struct _stp_iterator *iter)
{
        int cpu;

#ifdef STP_BULKMODE
        cpu = iter->cpu_file;
        if (iter->buffer_iter[cpu]) {
                if (ring_buffer_iter_empty(iter->buffer_iter[cpu]))
                        return 1;
        }
        else {
                if (atomic_read(&iter->nr_events) == 0)
                        return 1;
        }
        return 0;
#else
        for_each_online_cpu(cpu) {
                if (iter->buffer_iter[cpu]) {
                        if (!ring_buffer_iter_empty(iter->buffer_iter[cpu]))
                                return 0;
                }
                else {
                        if (atomic_read(&iter->nr_events) != 0)
                                return 0;
                }
        }
        return 1;
#endif
}

static int _stp_ring_buffer_empty(void)
{
        struct _stp_iterator *iter;
#ifdef STP_BULKMODE
        int cpu;

        for_each_possible_cpu(cpu) {
                iter = &_stp_relay_data.iter[cpu];
                if (! _stp_ring_buffer_empty_cpu(iter))
                        return 0;
        }
        return 1;
#else
        iter = &_stp_relay_data.iter[0];
        return _stp_ring_buffer_empty_cpu(iter);
#endif
}

static void _stp_ring_buffer_iterator_increment(struct _stp_iterator *iter)
{
        if (iter->buffer_iter[iter->cpu]) {
                _stp_ring_buffer_disable_cpu();
                ring_buffer_read(iter->buffer_iter[iter->cpu], NULL);
                _stp_ring_buffer_enable_cpu();
        }
}

static void _stp_ring_buffer_consume(struct _stp_iterator *iter)
{
        _stp_ring_buffer_iterator_increment(iter);
        _stp_ring_buffer_disable_cpu();
        ring_buffer_consume(_stp_relay_data.rb, iter->cpu, &iter->ts);
        _stp_ring_buffer_enable_cpu();
        atomic_dec(&iter->nr_events);
}

static ssize_t _stp_tracing_wait_pipe(struct file *filp)
{
        struct _stp_iterator *iter = filp->private_data;

        if (atomic_read(&iter->nr_events) == 0) {
                if ((filp->f_flags & O_NONBLOCK)) {
                        dbug_trans(1, "returning -EAGAIN\n");
                        return -EAGAIN;
                }

                if (signal_pending(current)) {
                        dbug_trans(1, "returning -EINTR\n");
                        return -EINTR;
                }
                dbug_trans(1, "returning 0\n");
                return 0;
        }

        dbug_trans(1, "returning 1\n");
        return 1;
}

static struct ring_buffer_event *
_stp_peek_next_event(struct _stp_iterator *iter, int cpu, u64 *ts)
{
        struct ring_buffer_event *event;

        _stp_ring_buffer_disable_cpu();
        if (iter->buffer_iter[cpu])
                event = ring_buffer_iter_peek(iter->buffer_iter[cpu], ts);
        else
                event = ring_buffer_peek(_stp_relay_data.rb, cpu, ts);
        _stp_ring_buffer_enable_cpu();
        return event;
}

/* Find the next real event */
static struct ring_buffer_event *
_stp_find_next_event(struct _stp_iterator *iter)
{
        struct ring_buffer_event *event;

#ifdef STP_BULKMODE
        int cpu_file = iter->cpu_file;

        /*
         * If we are in a per_cpu trace file, don't bother by iterating over
         * all cpus and peek directly.
         */
        if (iter->buffer_iter[cpu_file] == NULL ) {
                if (atomic_read(&iter->nr_events) == 0)
                        return NULL;
        }
        else {
                if (ring_buffer_iter_empty(iter->buffer_iter[cpu_file]))
                        return NULL;
        }
        event = _stp_peek_next_event(iter, cpu_file, &iter->ts);

        return event;
#else
        struct ring_buffer_event *next = NULL;
        u64 next_ts = 0, ts;
        int next_cpu = -1;
        int cpu;

        for_each_online_cpu(cpu) {
                if (iter->buffer_iter[cpu] == NULL ) {
                        if (atomic_read(&iter->nr_events) == 0)
                                continue;
                }
                else {
                        if (ring_buffer_iter_empty(iter->buffer_iter[cpu]))
                                continue;
                }

                event = _stp_peek_next_event(iter, cpu, &ts);

                /*
                 * Pick the event with the smallest timestamp:
                 */
                if (event && (!next || ts < next_ts)) {
                        next = event;
                        next_cpu = cpu;
                        next_ts = ts;
                }
        }

        iter->cpu = next_cpu;
        iter->ts = next_ts;
        return next;
#endif
}


static void
_stp_buffer_iter_finish(struct _stp_iterator *iter)
{
#ifdef STP_BULKMODE
        int cpu_file = iter->cpu_file;

        if (iter->buffer_iter[cpu_file]) {
                ring_buffer_read_finish(iter->buffer_iter[cpu_file]);
                iter->buffer_iter[cpu_file] = NULL;
        }
#else
        int cpu;

        for_each_possible_cpu(cpu) {
                if (iter->buffer_iter[cpu]) {
                        ring_buffer_read_finish(iter->buffer_iter[cpu]);
                        iter->buffer_iter[cpu] = NULL;
                }
        }
#endif
        dbug_trans(0, "iterator(s) finished\n");
}


static int
_stp_buffer_iter_start(struct _stp_iterator *iter)
{
#ifdef STP_BULKMODE
        int cpu_file = iter->cpu_file;

        iter->buffer_iter[cpu_file]
            = ring_buffer_read_start(_stp_relay_data.rb, cpu_file);
        if (iter->buffer_iter[cpu_file] == NULL) {
                dbug_trans(0, "buffer_iter[%d] was NULL\n", cpu_file);
                return 1;
        }
        dbug_trans(0, "iterator(s) started\n");
        return 0;
#else
        int cpu;

        for_each_online_cpu(cpu) {
                iter->buffer_iter[cpu]
                    = ring_buffer_read_start(_stp_relay_data.rb, cpu);
                if (iter->buffer_iter[cpu] == NULL) {
                        dbug_trans(0, "buffer_iter[%d] was NULL\n", cpu);
                        _stp_buffer_iter_finish(iter);
                        return 1;
                }
        }
        dbug_trans(0, "iterator(s) started\n");
        return 0;
#endif
}


/*
 * Consumer reader.
 */
static ssize_t
_stp_data_read_trace(struct file *filp, char __user *ubuf,
                     size_t cnt, loff_t *ppos)
{
        ssize_t sret = 0;
        struct ring_buffer_event *event;
        struct _stp_iterator *iter = filp->private_data;
#ifdef STP_BULKMODE
        int cpu_file = iter->cpu_file;
#else
        int cpu;
#endif

        dbug_trans(1, "%lu\n", (unsigned long)cnt);
        sret = _stp_tracing_wait_pipe(filp);
        dbug_trans(1, "_stp_tracing_wait_pipe returned %ld\n", sret);
        if (sret <= 0)
                goto out;

        if (cnt >= PAGE_SIZE)
                cnt = PAGE_SIZE - 1;

        dbug_trans(1, "sret = %lu\n", (unsigned long)sret);
        sret = 0;
        iter->ts = 0;
#ifdef USE_ITERS
        if (_stp_buffer_iter_start(iter))
                goto out;
#endif
        while ((event = _stp_find_next_event(iter)) != NULL) {
                ssize_t len;

#ifdef USE_ITERS
                _stp_buffer_iter_finish(iter);
#endif
                len = _stp_event_to_user(event, ubuf, cnt);
                if (len <= 0)
                        break;

                _stp_ring_buffer_consume(iter);
                dbug_trans(1, "event consumed\n");
                ubuf += len;
                cnt -= len;
                sret += len;
                if (cnt <= 0)
                        break;
#ifdef USE_ITERS
                if (_stp_buffer_iter_start(iter))
                        break;
#endif
        }

#ifdef USE_ITERS
        _stp_buffer_iter_finish(iter);
#endif
out:
        return sret;
}


static unsigned int
_stp_data_poll_trace(struct file *filp, poll_table *poll_table)
{
        struct _stp_iterator *iter = filp->private_data;

        dbug_trans(1, "entry\n");
        if (! _stp_ring_buffer_empty_cpu(iter))
                return POLLIN | POLLRDNORM;
        poll_wait(filp, &_stp_poll_wait, poll_table);
        if (! _stp_ring_buffer_empty_cpu(iter))
                return POLLIN | POLLRDNORM;

        dbug_trans(1, "exit\n");
        return 0;
}

static struct file_operations __stp_data_fops = {
        .owner          = THIS_MODULE,
        .open           = _stp_data_open_trace,
        .release        = _stp_data_release_trace,
        .poll           = _stp_data_poll_trace,
        .read           = _stp_data_read_trace,
};

static struct _stp_iterator *_stp_get_iterator(void)
{
#ifdef STP_BULKMODE
        int cpu = raw_smp_processor_id();
        return &_stp_relay_data.iter[cpu];
#else
        return &_stp_relay_data.iter[0];
#endif
}

/*
 * Here's how __STP_MAX_RESERVE_SIZE is figured.  The value of
 * BUF_PAGE_SIZE was gotten from the kernel's ring_buffer code.  It
 * is divided by 4, so we waste a maximum of 1/4 of the buffer (in
 * the case of a small reservation).
 */
#define __STP_MAX_RESERVE_SIZE ((/*BUF_PAGE_SIZE*/ 4080 / 4)    \
                                - sizeof(struct _stp_data_entry) \
                                - sizeof(struct ring_buffer_event))

/*
 * This function prepares the cpu buffer to write a sample.
 *
 * Struct op_entry is used during operations on the ring buffer while
 * struct op_sample contains the data that is stored in the ring
 * buffer. Struct entry can be uninitialized. The function reserves a
 * data array that is specified by size. Use
 * op_cpu_buffer_write_commit() after preparing the sample. In case of
 * errors a null pointer is returned, otherwise the pointer to the
 * sample.
 *
 */
static size_t
_stp_data_write_reserve(size_t size_request, void **entry)
{
        struct ring_buffer_event *event;
        struct _stp_data_entry *sde;
        struct _stp_iterator *iter = _stp_get_iterator();

        if (entry == NULL)
                return -EINVAL;

        if (size_request > __STP_MAX_RESERVE_SIZE) {
                size_request = __STP_MAX_RESERVE_SIZE;
        }

        if (_stp_ring_buffer_cpu_disabled()) {
                dbug_trans(0, "cpu disabled\n");
                entry = NULL;
                return 0;
        }

#ifdef STAPCONF_RING_BUFFER_FLAGS
        event = ring_buffer_lock_reserve(_stp_relay_data.rb,
                                         (sizeof(struct _stp_data_entry)
                                          + size_request), 0);
#else
        event = ring_buffer_lock_reserve(_stp_relay_data.rb,
                                         (sizeof(struct _stp_data_entry)
                                          + size_request));
#endif

        if (unlikely(! event)) {
                dbug_trans(0, "event = NULL (%p)?\n", event);
                if (! _stp_relay_data.overwrite_flag) {
                        entry = NULL;
                        return 0;
                }

                if (_stp_buffer_iter_start(iter)) {
                        entry = NULL;
                        return 0;
                }

                /* If we're in overwrite mode and all the buffers are
                 * full, take a event out of the buffer and consume it
                 * (throw it away).  This should make room for the new
                 * data. */
                event = _stp_find_next_event(iter);
                if (event) {
                        ssize_t len;

                        sde = ring_buffer_event_data(event);
                        if (sde->len < size_request)
                                size_request = sde->len;
                        _stp_ring_buffer_consume(iter);
                        _stp_buffer_iter_finish(iter);

                        /* Try to reserve again. */
#ifdef STAPCONF_RING_BUFFER_FLAGS
                        event = ring_buffer_lock_reserve(_stp_relay_data.rb,
                                                         sizeof(struct _stp_data_entry) + size_request,
                                                         0);
#else
                        event = ring_buffer_lock_reserve(_stp_relay_data.rb,
                                                         sizeof(struct _stp_data_entry) + size_request);
#endif
                        dbug_trans(0, "overwritten event = 0x%p\n", event);
                }
                else {
                        _stp_buffer_iter_finish(iter);
                }

                if (unlikely(! event)) {
                        entry = NULL;
                        return 0;
                }
        }

        sde = ring_buffer_event_data(event);
        sde->len = size_request;
        
        *entry = event;
        return size_request;
}

static unsigned char *_stp_data_entry_data(void *entry)
{
        struct ring_buffer_event *event = entry;
        struct _stp_data_entry *sde;

        if (event == NULL)
                return NULL;

        sde = ring_buffer_event_data(event);
        return sde->buf;
}

static int _stp_data_write_commit(void *entry)
{
        struct ring_buffer_event *event = (struct ring_buffer_event *)entry;

        if (unlikely(! entry)) {
                dbug_trans(1, "entry = NULL, returning -EINVAL\n");
                return -EINVAL;
        }

#if defined(DEBUG_TRANS) && (DEBUG_TRANS >= 2)
        {
                struct _stp_data_entry *sde = ring_buffer_event_data(event);
                char *last = sde->buf + (sde->len - 5);
                dbug_trans2("commiting %.5s...%.5s\n", sde->buf, last);
        }
#endif
        atomic_inc(&(_stp_get_iterator()->nr_events));

#ifdef STAPCONF_RING_BUFFER_FLAGS
        return ring_buffer_unlock_commit(_stp_relay_data.rb, event, 0);
#else
        return ring_buffer_unlock_commit(_stp_relay_data.rb, event);
#endif
}

static void __stp_relay_wakeup_timer(unsigned long val)
{
        if (waitqueue_active(&_stp_poll_wait) && ! _stp_ring_buffer_empty())
                wake_up_interruptible(&_stp_poll_wait);
        if (atomic_read(&_stp_relay_data.transport_state) == STP_TRANSPORT_RUNNING)
                mod_timer(&_stp_relay_data.timer, jiffies + STP_RELAY_TIMER_INTERVAL);
        else
                dbug_trans(0, "ring_buffer wakeup timer expiry\n");
}

static void __stp_relay_timer_start(void)
{
        init_timer(&_stp_relay_data.timer);
        _stp_relay_data.timer.expires = jiffies + STP_RELAY_TIMER_INTERVAL;
        _stp_relay_data.timer.function = __stp_relay_wakeup_timer;
        _stp_relay_data.timer.data = 0;
        add_timer(&_stp_relay_data.timer);
        smp_mb();
}

static void __stp_relay_timer_stop(void)
{
        del_timer_sync(&_stp_relay_data.timer);
}

static struct dentry *__stp_entry[NR_CPUS] = { NULL };

static int _stp_transport_data_fs_init(void)
{
        int rc;
        int cpu, cpu2;

        atomic_set (&_stp_relay_data.transport_state, STP_TRANSPORT_STOPPED);
        _stp_relay_data.rb = NULL;

        // allocate buffer
        dbug_trans(1, "entry...\n");
        rc = __stp_alloc_ring_buffer();
        if (rc != 0)
                return rc;

        // create file(s)
        for_each_online_cpu(cpu) {
                char cpu_file[9];       /* 5(trace) + 3(XXX) + 1(\0) = 9 */

                if (cpu > 999 || cpu < 0) {
                        _stp_transport_data_fs_close();
                        return -EINVAL;
                }
                snprintf(cpu_file, sizeof(cpu_file), "trace%d", cpu);
                __stp_entry[cpu] = debugfs_create_file(cpu_file, 0600,
                                                       _stp_get_module_dir(),
                                                       (void *)(long)cpu,
                                                       &__stp_data_fops);

                if (!__stp_entry[cpu]) {
                        pr_warning("Could not create debugfs 'trace' entry\n");
                        __stp_free_ring_buffer();
                        return -ENOENT;
                }
                else if (IS_ERR(__stp_entry[cpu])) {
                        rc = PTR_ERR(__stp_entry[cpu]);
                        pr_warning("Could not create debugfs 'trace' entry\n");
                        __stp_free_ring_buffer();
                        return rc;
                }

                __stp_entry[cpu]->d_inode->i_uid = _stp_uid;
                __stp_entry[cpu]->d_inode->i_gid = _stp_gid;
                __stp_entry[cpu]->d_inode->i_private = &_stp_relay_data.iter[cpu];

#ifndef STP_BULKMODE
                break;
#endif
        }

        for_each_possible_cpu(cpu) {
#ifdef STP_BULKMODE
                _stp_relay_data.iter[cpu].cpu_file = cpu;
                _stp_relay_data.iter[cpu].cpu = cpu;
#endif
                for_each_possible_cpu(cpu2) {
                        _stp_relay_data.iter[cpu].buffer_iter[cpu2] = NULL;
                }

                atomic_set(&_stp_relay_data.iter[cpu].nr_events, 0);

#ifndef STP_BULKMODE
                break;
#endif
        }

        dbug_trans(1, "returning 0...\n");
        atomic_set (&_stp_relay_data.transport_state, STP_TRANSPORT_INITIALIZED);
        return 0;
}

static void _stp_transport_data_fs_start(void)
{
        if (atomic_read(&_stp_relay_data.transport_state) == STP_TRANSPORT_INITIALIZED) {
                atomic_set(&_stp_relay_data.transport_state, STP_TRANSPORT_RUNNING);
                __stp_relay_timer_start();
        }
}

static void _stp_transport_data_fs_stop(void)
{
        if (atomic_read(&_stp_relay_data.transport_state) == STP_TRANSPORT_RUNNING) {
                atomic_set(&_stp_relay_data.transport_state, STP_TRANSPORT_STOPPED);
                __stp_relay_timer_stop();
        }
}

static void _stp_transport_data_fs_close(void)
{
        int cpu;

        for_each_possible_cpu(cpu) {
                if (__stp_entry[cpu])
                        debugfs_remove(__stp_entry[cpu]);
                __stp_entry[cpu] = NULL;
        }

        __stp_free_ring_buffer();
}

static enum _stp_transport_state _stp_transport_get_state(void)
{
        return atomic_read (&_stp_relay_data.transport_state);
}

static void _stp_transport_data_fs_overwrite(int overwrite)
{
        dbug_trans(0, "setting ovewrite to %d\n", overwrite);
        _stp_relay_data.overwrite_flag = overwrite;
}