spu_task_sync.c

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/*
 * Cell Broadband Engine OProfile Support
 *
 * (C) Copyright IBM Corporation 2006
 *
 * Author: Maynard Johnson <[email protected]>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

/* The purpose of this file is to handle SPU event task switching
 * and to record SPU context information into the OProfile
 * event buffer.
 *
 * Additionally, the spu_sync_buffer function is provided as a helper
 * for recoding actual SPU program counter samples to the event buffer.
 */
#include <linux/dcookies.h>
#include <linux/kref.h>
#include <linux/mm.h>
#include <linux/fs.h>
#include <linux/module.h>
#include <linux/notifier.h>
#include <linux/numa.h>
#include <linux/oprofile.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include "pr_util.h"

#define RELEASE_ALL 9999

static DEFINE_SPINLOCK(buffer_lock);
static DEFINE_SPINLOCK(cache_lock);
static int num_spu_nodes;
int spu_prof_num_nodes;

struct spu_buffer spu_buff[MAX_NUMNODES * SPUS_PER_NODE];
struct delayed_work spu_work;
static unsigned max_spu_buff;

static void spu_buff_add(unsigned long int value, int spu)
{
    /* spu buff is a circular buffer.  Add entries to the
     * head.  Head is the index to store the next value.
     * The buffer is full when there is one available entry
     * in the queue, i.e. head and tail can't be equal.
     * That way we can tell the difference between the
     * buffer being full versus empty.
     *
     *  ASSUPTION: the buffer_lock is held when this function
     *             is called to lock the buffer, head and tail.
     */
    int full = 1;

    if (spu_buff[spu].head >= spu_buff[spu].tail) {
        if ((spu_buff[spu].head - spu_buff[spu].tail)
            <  (max_spu_buff - 1))
            full = 0;

    } else if (spu_buff[spu].tail > spu_buff[spu].head) {
        if ((spu_buff[spu].tail - spu_buff[spu].head)
            > 1)
            full = 0;
    }

    if (!full) {
        spu_buff[spu].buff[spu_buff[spu].head] = value;
        spu_buff[spu].head++;

        if (spu_buff[spu].head >= max_spu_buff)
            spu_buff[spu].head = 0;
    } else {
        /* From the user's perspective make the SPU buffer
         * size management/overflow look like we are using
         * per cpu buffers.  The user uses the same
         * per cpu parameter to adjust the SPU buffer size.
         * Increment the sample_lost_overflow to inform
         * the user the buffer size needs to be increased.
         */
        oprofile_cpu_buffer_inc_smpl_lost();
    }
}

/* This function copies the per SPU buffers to the
 * OProfile kernel buffer.
 */
void sync_spu_buff(void)
{
    int spu;
    unsigned long flags;
    int curr_head;

    for (spu = 0; spu < num_spu_nodes; spu++) {
        /* In case there was an issue and the buffer didn't
         * get created skip it.
         */
        if (spu_buff[spu].buff == NULL)
            continue;

        /* Hold the lock to make sure the head/tail
         * doesn't change while spu_buff_add() is
         * deciding if the buffer is full or not.
         * Being a little paranoid.
         */
        spin_lock_irqsave(&buffer_lock, flags);
        curr_head = spu_buff[spu].head;
        spin_unlock_irqrestore(&buffer_lock, flags);

        /* Transfer the current contents to the kernel buffer.
         * data can still be added to the head of the buffer.
         */
        oprofile_put_buff(spu_buff[spu].buff,
                  spu_buff[spu].tail,
                  curr_head, max_spu_buff);

        spin_lock_irqsave(&buffer_lock, flags);
        spu_buff[spu].tail = curr_head;
        spin_unlock_irqrestore(&buffer_lock, flags);
    }

}

static void wq_sync_spu_buff(struct work_struct *work)
{
    /* move data from spu buffers to kernel buffer */
    sync_spu_buff();

    /* only reschedule if profiling is not done */
    if (spu_prof_running)
        schedule_delayed_work(&spu_work, DEFAULT_TIMER_EXPIRE);
}

/* Container for caching information about an active SPU task. */
struct cached_info {
    struct vma_to_fileoffset_map *map;
    struct spu *the_spu;    /* needed to access pointer to local_store */
    struct kref cache_ref;
};

static struct cached_info *spu_info[MAX_NUMNODES * 8];

static void destroy_cached_info(struct kref *kref)
{
    struct cached_info *info;

    info = container_of(kref, struct cached_info, cache_ref);
    vma_map_free(info->map);
    kfree(info);
    module_put(THIS_MODULE);
}

/* Return the cached_info for the passed SPU number.
 * ATTENTION:  Callers are responsible for obtaining the
 *         cache_lock if needed prior to invoking this function.
 */
static struct cached_info *get_cached_info(struct spu *the_spu, int spu_num)
{
    struct kref *ref;
    struct cached_info *ret_info;

    if (spu_num >= num_spu_nodes) {
        printk(KERN_ERR "SPU_PROF: "
               "%s, line %d: Invalid index %d into spu info cache\n",
               __func__, __LINE__, spu_num);
        ret_info = NULL;
        goto out;
    }
    if (!spu_info[spu_num] && the_spu) {
        ref = spu_get_profile_private_kref(the_spu->ctx);
        if (ref) {
            spu_info[spu_num] = container_of(ref, struct cached_info, cache_ref);
            kref_get(&spu_info[spu_num]->cache_ref);
        }
    }

    ret_info = spu_info[spu_num];
 out:
    return ret_info;
}


/* Looks for cached info for the passed spu.  If not found, the
 * cached info is created for the passed spu.
 * Returns 0 for success; otherwise, -1 for error.
 */
static int
prepare_cached_spu_info(struct spu *spu, unsigned long objectId)
{
    unsigned long flags;
    struct vma_to_fileoffset_map *new_map;
    int retval = 0;
    struct cached_info *info;

    /* We won't bother getting cache_lock here since
     * don't do anything with the cached_info that's returned.
     */
    info = get_cached_info(spu, spu->number);

    if (info) {
        pr_debug("Found cached SPU info.\n");
        goto out;
    }

    /* Create cached_info and set spu_info[spu->number] to point to it.
     * spu->number is a system-wide value, not a per-node value.
     */
    info = kzalloc(sizeof(struct cached_info), GFP_KERNEL);
    if (!info) {
        printk(KERN_ERR "SPU_PROF: "
               "%s, line %d: create vma_map failed\n",
               __func__, __LINE__);
        retval = -ENOMEM;
        goto err_alloc;
    }
    new_map = create_vma_map(spu, objectId);
    if (!new_map) {
        printk(KERN_ERR "SPU_PROF: "
               "%s, line %d: create vma_map failed\n",
               __func__, __LINE__);
        retval = -ENOMEM;
        goto err_alloc;
    }

    pr_debug("Created vma_map\n");
    info->map = new_map;
    info->the_spu = spu;
    kref_init(&info->cache_ref);
    spin_lock_irqsave(&cache_lock, flags);
    spu_info[spu->number] = info;
    /* Increment count before passing off ref to SPUFS. */
    kref_get(&info->cache_ref);

    /* We increment the module refcount here since SPUFS is
     * responsible for the final destruction of the cached_info,
     * and it must be able to access the destroy_cached_info()
     * function defined in the OProfile module.  We decrement
     * the module refcount in destroy_cached_info.
     */
    try_module_get(THIS_MODULE);
    spu_set_profile_private_kref(spu->ctx, &info->cache_ref,
                destroy_cached_info);
    spin_unlock_irqrestore(&cache_lock, flags);
    goto out;

err_alloc:
    kfree(info);
out:
    return retval;
}

/*
 * NOTE:  The caller is responsible for locking the
 *    cache_lock prior to calling this function.
 */
static int release_cached_info(int spu_index)
{
    int index, end;

    if (spu_index == RELEASE_ALL) {
        end = num_spu_nodes;
        index = 0;
    } else {
        if (spu_index >= num_spu_nodes) {
            printk(KERN_ERR "SPU_PROF: "
                "%s, line %d: "
                "Invalid index %d into spu info cache\n",
                __func__, __LINE__, spu_index);
            goto out;
        }
        end = spu_index + 1;
        index = spu_index;
    }
    for (; index < end; index++) {
        if (spu_info[index]) {
            kref_put(&spu_info[index]->cache_ref,
                 destroy_cached_info);
            spu_info[index] = NULL;
        }
    }

out:
    return 0;
}

/* The source code for fast_get_dcookie was "borrowed"
 * from drivers/oprofile/buffer_sync.c.
 */

/* Optimisation. We can manage without taking the dcookie sem
 * because we cannot reach this code without at least one
 * dcookie user still being registered (namely, the reader
 * of the event buffer).
 */
static inline unsigned long fast_get_dcookie(struct path *path)
{
    unsigned long cookie;

    if (path->dentry->d_flags & DCACHE_COOKIE)
        return (unsigned long)path->dentry;
    get_dcookie(path, &cookie);
    return cookie;
}

/* Look up the dcookie for the task's mm->exe_file,
 * which corresponds loosely to "application name". Also, determine
 * the offset for the SPU ELF object.  If computed offset is
 * non-zero, it implies an embedded SPU object; otherwise, it's a
 * separate SPU binary, in which case we retrieve it's dcookie.
 * For the embedded case, we must determine if SPU ELF is embedded
 * in the executable application or another file (i.e., shared lib).
 * If embedded in a shared lib, we must get the dcookie and return
 * that to the caller.
 */
static unsigned long
get_exec_dcookie_and_offset(struct spu *spu, unsigned int *offsetp,
                unsigned long *spu_bin_dcookie,
                unsigned long spu_ref)
{
    unsigned long app_cookie = 0;
    unsigned int my_offset = 0;
    struct vm_area_struct *vma;
    struct mm_struct *mm = spu->mm;

    if (!mm)
        goto out;

    down_read(&mm->mmap_sem);

    if (mm->exe_file) {
        app_cookie = fast_get_dcookie(&mm->exe_file->f_path);
        pr_debug("got dcookie for %s\n",
             mm->exe_file->f_dentry->d_name.name);
    }

    for (vma = mm->mmap; vma; vma = vma->vm_next) {
        if (vma->vm_start > spu_ref || vma->vm_end <= spu_ref)
            continue;
        my_offset = spu_ref - vma->vm_start;
        if (!vma->vm_file)
            goto fail_no_image_cookie;

        pr_debug("Found spu ELF at %X(object-id:%lx) for file %s\n",
             my_offset, spu_ref,
             vma->vm_file->f_dentry->d_name.name);
        *offsetp = my_offset;
        break;
    }

    *spu_bin_dcookie = fast_get_dcookie(&vma->vm_file->f_path);
    pr_debug("got dcookie for %s\n", vma->vm_file->f_dentry->d_name.name);

    up_read(&mm->mmap_sem);

out:
    return app_cookie;

fail_no_image_cookie:
    up_read(&mm->mmap_sem);

    printk(KERN_ERR "SPU_PROF: "
        "%s, line %d: Cannot find dcookie for SPU binary\n",
        __func__, __LINE__);
    goto out;
}



/* This function finds or creates cached context information for the
 * passed SPU and records SPU context information into the OProfile
 * event buffer.
 */
static int process_context_switch(struct spu *spu, unsigned long objectId)
{
    unsigned long flags;
    int retval;
    unsigned int offset = 0;
    unsigned long spu_cookie = 0, app_dcookie;

    retval = prepare_cached_spu_info(spu, objectId);
    if (retval)
        goto out;

    /* Get dcookie first because a mutex_lock is taken in that
     * code path, so interrupts must not be disabled.
     */
    app_dcookie = get_exec_dcookie_and_offset(spu, &offset, &spu_cookie, objectId);
    if (!app_dcookie || !spu_cookie) {
        retval  = -ENOENT;
        goto out;
    }

    /* Record context info in event buffer */
    spin_lock_irqsave(&buffer_lock, flags);
    spu_buff_add(ESCAPE_CODE, spu->number);
    spu_buff_add(SPU_CTX_SWITCH_CODE, spu->number);
    spu_buff_add(spu->number, spu->number);
    spu_buff_add(spu->pid, spu->number);
    spu_buff_add(spu->tgid, spu->number);
    spu_buff_add(app_dcookie, spu->number);
    spu_buff_add(spu_cookie, spu->number);
    spu_buff_add(offset, spu->number);

    /* Set flag to indicate SPU PC data can now be written out.  If
     * the SPU program counter data is seen before an SPU context
     * record is seen, the postprocessing will fail.
     */
    spu_buff[spu->number].ctx_sw_seen = 1;

    spin_unlock_irqrestore(&buffer_lock, flags);
    smp_wmb();  /* insure spu event buffer updates are written */
            /* don't want entries intermingled... */
out:
    return retval;
}

/*
 * This function is invoked on either a bind_context or unbind_context.
 * If called for an unbind_context, the val arg is 0; otherwise,
 * it is the object-id value for the spu context.
 * The data arg is of type 'struct spu *'.
 */
static int spu_active_notify(struct notifier_block *self, unsigned long val,
                void *data)
{
    int retval;
    unsigned long flags;
    struct spu *the_spu = data;

    pr_debug("SPU event notification arrived\n");
    if (!val) {
        spin_lock_irqsave(&cache_lock, flags);
        retval = release_cached_info(the_spu->number);
        spin_unlock_irqrestore(&cache_lock, flags);
    } else {
        retval = process_context_switch(the_spu, val);
    }
    return retval;
}

static struct notifier_block spu_active = {
    .notifier_call = spu_active_notify,
};

static int number_of_online_nodes(void)
{
        u32 cpu; u32 tmp;
        int nodes = 0;
        for_each_online_cpu(cpu) {
                tmp = cbe_cpu_to_node(cpu) + 1;
                if (tmp > nodes)
                        nodes++;
        }
        return nodes;
}

static int oprofile_spu_buff_create(void)
{
    int spu;

    max_spu_buff = oprofile_get_cpu_buffer_size();

    for (spu = 0; spu < num_spu_nodes; spu++) {
        /* create circular buffers to store the data in.
         * use locks to manage accessing the buffers
         */
        spu_buff[spu].head = 0;
        spu_buff[spu].tail = 0;

        /*
         * Create a buffer for each SPU.  Can't reliably
         * create a single buffer for all spus due to not
         * enough contiguous kernel memory.
         */

        spu_buff[spu].buff = kzalloc((max_spu_buff
                          * sizeof(unsigned long)),
                         GFP_KERNEL);

        if (!spu_buff[spu].buff) {
            printk(KERN_ERR "SPU_PROF: "
                   "%s, line %d:  oprofile_spu_buff_create "
               "failed to allocate spu buffer %d.\n",
                   __func__, __LINE__, spu);

            /* release the spu buffers that have been allocated */
            while (spu >= 0) {
                kfree(spu_buff[spu].buff);
                spu_buff[spu].buff = 0;
                spu--;
            }
            return -ENOMEM;
        }
    }
    return 0;
}

/* The main purpose of this function is to synchronize
 * OProfile with SPUFS by registering to be notified of
 * SPU task switches.
 *
 * NOTE: When profiling SPUs, we must ensure that only
 * spu_sync_start is invoked and not the generic sync_start
 * in drivers/oprofile/oprof.c.  A return value of
 * SKIP_GENERIC_SYNC or SYNC_START_ERROR will
 * accomplish this.
 */
int spu_sync_start(void)
{
    int spu;
    int ret = SKIP_GENERIC_SYNC;
    int register_ret;
    unsigned long flags = 0;

    spu_prof_num_nodes = number_of_online_nodes();
    num_spu_nodes = spu_prof_num_nodes * 8;
    INIT_DELAYED_WORK(&spu_work, wq_sync_spu_buff);

    /* create buffer for storing the SPU data to put in
     * the kernel buffer.
     */
    ret = oprofile_spu_buff_create();
    if (ret)
        goto out;

    spin_lock_irqsave(&buffer_lock, flags);
    for (spu = 0; spu < num_spu_nodes; spu++) {
        spu_buff_add(ESCAPE_CODE, spu);
        spu_buff_add(SPU_PROFILING_CODE, spu);
        spu_buff_add(num_spu_nodes, spu);
    }
    spin_unlock_irqrestore(&buffer_lock, flags);

    for (spu = 0; spu < num_spu_nodes; spu++) {
        spu_buff[spu].ctx_sw_seen = 0;
        spu_buff[spu].last_guard_val = 0;
    }

    /* Register for SPU events  */
    register_ret = spu_switch_event_register(&spu_active);
    if (register_ret) {
        ret = SYNC_START_ERROR;
        goto out;
    }

    pr_debug("spu_sync_start -- running.\n");
out:
    return ret;
}

/* Record SPU program counter samples to the oprofile event buffer. */
void spu_sync_buffer(int spu_num, unsigned int *samples,
             int num_samples)
{
    unsigned long long file_offset;
    unsigned long flags;
    int i;
    struct vma_to_fileoffset_map *map;
    struct spu *the_spu;
    unsigned long long spu_num_ll = spu_num;
    unsigned long long spu_num_shifted = spu_num_ll << 32;
    struct cached_info *c_info;

    /* We need to obtain the cache_lock here because it's
     * possible that after getting the cached_info, the SPU job
     * corresponding to this cached_info may end, thus resulting
     * in the destruction of the cached_info.
     */
    spin_lock_irqsave(&cache_lock, flags);
    c_info = get_cached_info(NULL, spu_num);
    if (!c_info) {
        /* This legitimately happens when the SPU task ends before all
         * samples are recorded.
         * No big deal -- so we just drop a few samples.
         */
        pr_debug("SPU_PROF: No cached SPU contex "
              "for SPU #%d. Dropping samples.\n", spu_num);
        goto out;
    }

    map = c_info->map;
    the_spu = c_info->the_spu;
    spin_lock(&buffer_lock);
    for (i = 0; i < num_samples; i++) {
        unsigned int sample = *(samples+i);
        int grd_val = 0;
        file_offset = 0;
        if (sample == 0)
            continue;
        file_offset = vma_map_lookup( map, sample, the_spu, &grd_val);

        /* If overlays are used by this SPU application, the guard
         * value is non-zero, indicating which overlay section is in
         * use.  We need to discard samples taken during the time
         * period which an overlay occurs (i.e., guard value changes).
         */
        if (grd_val && grd_val != spu_buff[spu_num].last_guard_val) {
            spu_buff[spu_num].last_guard_val = grd_val;
            /* Drop the rest of the samples. */
            break;
        }

        /* We must ensure that the SPU context switch has been written
         * out before samples for the SPU.  Otherwise, the SPU context
         * information is not available and the postprocessing of the
         * SPU PC will fail with no available anonymous map information.
         */
        if (spu_buff[spu_num].ctx_sw_seen)
            spu_buff_add((file_offset | spu_num_shifted),
                     spu_num);
    }
    spin_unlock(&buffer_lock);
out:
    spin_unlock_irqrestore(&cache_lock, flags);
}


int spu_sync_stop(void)
{
    unsigned long flags = 0;
    int ret;
    int k;

    ret = spu_switch_event_unregister(&spu_active);

    if (ret)
        printk(KERN_ERR "SPU_PROF: "
               "%s, line %d: spu_switch_event_unregister "  \
               "returned %d\n",
               __func__, __LINE__, ret);

    /* flush any remaining data in the per SPU buffers */
    sync_spu_buff();

    spin_lock_irqsave(&cache_lock, flags);
    ret = release_cached_info(RELEASE_ALL);
    spin_unlock_irqrestore(&cache_lock, flags);

    /* remove scheduled work queue item rather then waiting
     * for every queued entry to execute.  Then flush pending
     * system wide buffer to event buffer.
     */
    cancel_delayed_work(&spu_work);

    for (k = 0; k < num_spu_nodes; k++) {
        spu_buff[k].ctx_sw_seen = 0;

        /*
         * spu_sys_buff will be null if there was a problem
         * allocating the buffer.  Only delete if it exists.
         */
        kfree(spu_buff[k].buff);
        spu_buff[k].buff = 0;
    }
    pr_debug("spu_sync_stop -- done.\n");
    return ret;
}