ehca_irq.c

Go to the documentation of this file.

/*
 *  IBM eServer eHCA Infiniband device driver for Linux on POWER
 *
 *  Functions for EQs, NEQs and interrupts
 *
 *  Authors: Heiko J Schick <[email protected]>
 *           Khadija Souissi <[email protected]>
 *           Hoang-Nam Nguyen <[email protected]>
 *           Joachim Fenkes <[email protected]>
 *
 *  Copyright (c) 2005 IBM Corporation
 *
 *  All rights reserved.
 *
 *  This source code is distributed under a dual license of GPL v2.0 and OpenIB
 *  BSD.
 *
 * OpenIB BSD License
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * Redistributions of source code must retain the above copyright notice, this
 * list of conditions and the following disclaimer.
 *
 * Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials
 * provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
 * IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include <linux/slab.h>
#include <linux/smpboot.h>

#include "ehca_classes.h"
#include "ehca_irq.h"
#include "ehca_iverbs.h"
#include "ehca_tools.h"
#include "hcp_if.h"
#include "hipz_fns.h"
#include "ipz_pt_fn.h"

#define EQE_COMPLETION_EVENT   EHCA_BMASK_IBM( 1,  1)
#define EQE_CQ_QP_NUMBER       EHCA_BMASK_IBM( 8, 31)
#define EQE_EE_IDENTIFIER      EHCA_BMASK_IBM( 2,  7)
#define EQE_CQ_NUMBER          EHCA_BMASK_IBM( 8, 31)
#define EQE_QP_NUMBER          EHCA_BMASK_IBM( 8, 31)
#define EQE_QP_TOKEN           EHCA_BMASK_IBM(32, 63)
#define EQE_CQ_TOKEN           EHCA_BMASK_IBM(32, 63)

#define NEQE_COMPLETION_EVENT  EHCA_BMASK_IBM( 1,  1)
#define NEQE_EVENT_CODE        EHCA_BMASK_IBM( 2,  7)
#define NEQE_PORT_NUMBER       EHCA_BMASK_IBM( 8, 15)
#define NEQE_PORT_AVAILABILITY EHCA_BMASK_IBM(16, 16)
#define NEQE_DISRUPTIVE        EHCA_BMASK_IBM(16, 16)
#define NEQE_SPECIFIC_EVENT    EHCA_BMASK_IBM(16, 23)

#define ERROR_DATA_LENGTH      EHCA_BMASK_IBM(52, 63)
#define ERROR_DATA_TYPE        EHCA_BMASK_IBM( 0,  7)

static void queue_comp_task(struct ehca_cq *__cq);

static struct ehca_comp_pool *pool;

static inline void comp_event_callback(struct ehca_cq *cq)
{
    if (!cq->ib_cq.comp_handler)
        return;

    spin_lock(&cq->cb_lock);
    cq->ib_cq.comp_handler(&cq->ib_cq, cq->ib_cq.cq_context);
    spin_unlock(&cq->cb_lock);

    return;
}

static void print_error_data(struct ehca_shca *shca, void *data,
                 u64 *rblock, int length)
{
    u64 type = EHCA_BMASK_GET(ERROR_DATA_TYPE, rblock[2]);
    u64 resource = rblock[1];

    switch (type) {
    case 0x1: /* Queue Pair */
    {
        struct ehca_qp *qp = (struct ehca_qp *)data;

        /* only print error data if AER is set */
        if (rblock[6] == 0)
            return;

        ehca_err(&shca->ib_device,
             "QP 0x%x (resource=%llx) has errors.",
             qp->ib_qp.qp_num, resource);
        break;
    }
    case 0x4: /* Completion Queue */
    {
        struct ehca_cq *cq = (struct ehca_cq *)data;

        ehca_err(&shca->ib_device,
             "CQ 0x%x (resource=%llx) has errors.",
             cq->cq_number, resource);
        break;
    }
    default:
        ehca_err(&shca->ib_device,
             "Unknown error type: %llx on %s.",
             type, shca->ib_device.name);
        break;
    }

    ehca_err(&shca->ib_device, "Error data is available: %llx.", resource);
    ehca_err(&shca->ib_device, "EHCA ----- error data begin "
         "---------------------------------------------------");
    ehca_dmp(rblock, length, "resource=%llx", resource);
    ehca_err(&shca->ib_device, "EHCA ----- error data end "
         "----------------------------------------------------");

    return;
}

int ehca_error_data(struct ehca_shca *shca, void *data,
            u64 resource)
{

    unsigned long ret;
    u64 *rblock;
    unsigned long block_count;

    rblock = ehca_alloc_fw_ctrlblock(GFP_ATOMIC);
    if (!rblock) {
        ehca_err(&shca->ib_device, "Cannot allocate rblock memory.");
        ret = -ENOMEM;
        goto error_data1;
    }

    /* rblock must be 4K aligned and should be 4K large */
    ret = hipz_h_error_data(shca->ipz_hca_handle,
                resource,
                rblock,
                &block_count);

    if (ret == H_R_STATE)
        ehca_err(&shca->ib_device,
             "No error data is available: %llx.", resource);
    else if (ret == H_SUCCESS) {
        int length;

        length = EHCA_BMASK_GET(ERROR_DATA_LENGTH, rblock[0]);

        if (length > EHCA_PAGESIZE)
            length = EHCA_PAGESIZE;

        print_error_data(shca, data, rblock, length);
    } else
        ehca_err(&shca->ib_device,
             "Error data could not be fetched: %llx", resource);

    ehca_free_fw_ctrlblock(rblock);

error_data1:
    return ret;

}

static void dispatch_qp_event(struct ehca_shca *shca, struct ehca_qp *qp,
                  enum ib_event_type event_type)
{
    struct ib_event event;

    /* PATH_MIG without the QP ever having been armed is false alarm */
    if (event_type == IB_EVENT_PATH_MIG && !qp->mig_armed)
        return;

    event.device = &shca->ib_device;
    event.event = event_type;

    if (qp->ext_type == EQPT_SRQ) {
        if (!qp->ib_srq.event_handler)
            return;

        event.element.srq = &qp->ib_srq;
        qp->ib_srq.event_handler(&event, qp->ib_srq.srq_context);
    } else {
        if (!qp->ib_qp.event_handler)
            return;

        event.element.qp = &qp->ib_qp;
        qp->ib_qp.event_handler(&event, qp->ib_qp.qp_context);
    }
}

static void qp_event_callback(struct ehca_shca *shca, u64 eqe,
                  enum ib_event_type event_type, int fatal)
{
    struct ehca_qp *qp;
    u32 token = EHCA_BMASK_GET(EQE_QP_TOKEN, eqe);

    read_lock(&ehca_qp_idr_lock);
    qp = idr_find(&ehca_qp_idr, token);
    if (qp)
        atomic_inc(&qp->nr_events);
    read_unlock(&ehca_qp_idr_lock);

    if (!qp)
        return;

    if (fatal)
        ehca_error_data(shca, qp, qp->ipz_qp_handle.handle);

    dispatch_qp_event(shca, qp, fatal && qp->ext_type == EQPT_SRQ ?
              IB_EVENT_SRQ_ERR : event_type);

    /*
     * eHCA only processes one WQE at a time for SRQ base QPs,
     * so the last WQE has been processed as soon as the QP enters
     * error state.
     */
    if (fatal && qp->ext_type == EQPT_SRQBASE)
        dispatch_qp_event(shca, qp, IB_EVENT_QP_LAST_WQE_REACHED);

    if (atomic_dec_and_test(&qp->nr_events))
        wake_up(&qp->wait_completion);
    return;
}

static void cq_event_callback(struct ehca_shca *shca,
                  u64 eqe)
{
    struct ehca_cq *cq;
    u32 token = EHCA_BMASK_GET(EQE_CQ_TOKEN, eqe);

    read_lock(&ehca_cq_idr_lock);
    cq = idr_find(&ehca_cq_idr, token);
    if (cq)
        atomic_inc(&cq->nr_events);
    read_unlock(&ehca_cq_idr_lock);

    if (!cq)
        return;

    ehca_error_data(shca, cq, cq->ipz_cq_handle.handle);

    if (atomic_dec_and_test(&cq->nr_events))
        wake_up(&cq->wait_completion);

    return;
}

static void parse_identifier(struct ehca_shca *shca, u64 eqe)
{
    u8 identifier = EHCA_BMASK_GET(EQE_EE_IDENTIFIER, eqe);

    switch (identifier) {
    case 0x02: /* path migrated */
        qp_event_callback(shca, eqe, IB_EVENT_PATH_MIG, 0);
        break;
    case 0x03: /* communication established */
        qp_event_callback(shca, eqe, IB_EVENT_COMM_EST, 0);
        break;
    case 0x04: /* send queue drained */
        qp_event_callback(shca, eqe, IB_EVENT_SQ_DRAINED, 0);
        break;
    case 0x05: /* QP error */
    case 0x06: /* QP error */
        qp_event_callback(shca, eqe, IB_EVENT_QP_FATAL, 1);
        break;
    case 0x07: /* CQ error */
    case 0x08: /* CQ error */
        cq_event_callback(shca, eqe);
        break;
    case 0x09: /* MRMWPTE error */
        ehca_err(&shca->ib_device, "MRMWPTE error.");
        break;
    case 0x0A: /* port event */
        ehca_err(&shca->ib_device, "Port event.");
        break;
    case 0x0B: /* MR access error */
        ehca_err(&shca->ib_device, "MR access error.");
        break;
    case 0x0C: /* EQ error */
        ehca_err(&shca->ib_device, "EQ error.");
        break;
    case 0x0D: /* P/Q_Key mismatch */
        ehca_err(&shca->ib_device, "P/Q_Key mismatch.");
        break;
    case 0x10: /* sampling complete */
        ehca_err(&shca->ib_device, "Sampling complete.");
        break;
    case 0x11: /* unaffiliated access error */
        ehca_err(&shca->ib_device, "Unaffiliated access error.");
        break;
    case 0x12: /* path migrating */
        ehca_err(&shca->ib_device, "Path migrating.");
        break;
    case 0x13: /* interface trace stopped */
        ehca_err(&shca->ib_device, "Interface trace stopped.");
        break;
    case 0x14: /* first error capture info available */
        ehca_info(&shca->ib_device, "First error capture available");
        break;
    case 0x15: /* SRQ limit reached */
        qp_event_callback(shca, eqe, IB_EVENT_SRQ_LIMIT_REACHED, 0);
        break;
    default:
        ehca_err(&shca->ib_device, "Unknown identifier: %x on %s.",
             identifier, shca->ib_device.name);
        break;
    }

    return;
}

static void dispatch_port_event(struct ehca_shca *shca, int port_num,
                enum ib_event_type type, const char *msg)
{
    struct ib_event event;

    ehca_info(&shca->ib_device, "port %d %s.", port_num, msg);
    event.device = &shca->ib_device;
    event.event = type;
    event.element.port_num = port_num;
    ib_dispatch_event(&event);
}

static void notify_port_conf_change(struct ehca_shca *shca, int port_num)
{
    struct ehca_sma_attr  new_attr;
    struct ehca_sma_attr *old_attr = &shca->sport[port_num - 1].saved_attr;

    ehca_query_sma_attr(shca, port_num, &new_attr);

    if (new_attr.sm_sl  != old_attr->sm_sl ||
        new_attr.sm_lid != old_attr->sm_lid)
        dispatch_port_event(shca, port_num, IB_EVENT_SM_CHANGE,
                    "SM changed");

    if (new_attr.lid != old_attr->lid ||
        new_attr.lmc != old_attr->lmc)
        dispatch_port_event(shca, port_num, IB_EVENT_LID_CHANGE,
                    "LID changed");

    if (new_attr.pkey_tbl_len != old_attr->pkey_tbl_len ||
        memcmp(new_attr.pkeys, old_attr->pkeys,
           sizeof(u16) * new_attr.pkey_tbl_len))
        dispatch_port_event(shca, port_num, IB_EVENT_PKEY_CHANGE,
                    "P_Key changed");

    *old_attr = new_attr;
}

/* replay modify_qp for sqps -- return 0 if all is well, 1 if AQP1 destroyed */
static int replay_modify_qp(struct ehca_sport *sport)
{
    int aqp1_destroyed;
    unsigned long flags;

    spin_lock_irqsave(&sport->mod_sqp_lock, flags);

    aqp1_destroyed = !sport->ibqp_sqp[IB_QPT_GSI];

    if (sport->ibqp_sqp[IB_QPT_SMI])
        ehca_recover_sqp(sport->ibqp_sqp[IB_QPT_SMI]);
    if (!aqp1_destroyed)
        ehca_recover_sqp(sport->ibqp_sqp[IB_QPT_GSI]);

    spin_unlock_irqrestore(&sport->mod_sqp_lock, flags);

    return aqp1_destroyed;
}

static void parse_ec(struct ehca_shca *shca, u64 eqe)
{
    u8 ec   = EHCA_BMASK_GET(NEQE_EVENT_CODE, eqe);
    u8 port = EHCA_BMASK_GET(NEQE_PORT_NUMBER, eqe);
    u8 spec_event;
    struct ehca_sport *sport = &shca->sport[port - 1];

    switch (ec) {
    case 0x30: /* port availability change */
        if (EHCA_BMASK_GET(NEQE_PORT_AVAILABILITY, eqe)) {
            /* only replay modify_qp calls in autodetect mode;
             * if AQP1 was destroyed, the port is already down
             * again and we can drop the event.
             */
            if (ehca_nr_ports < 0)
                if (replay_modify_qp(sport))
                    break;

            sport->port_state = IB_PORT_ACTIVE;
            dispatch_port_event(shca, port, IB_EVENT_PORT_ACTIVE,
                        "is active");
            ehca_query_sma_attr(shca, port, &sport->saved_attr);
        } else {
            sport->port_state = IB_PORT_DOWN;
            dispatch_port_event(shca, port, IB_EVENT_PORT_ERR,
                        "is inactive");
        }
        break;
    case 0x31:
        /* port configuration change
         * disruptive change is caused by
         * LID, PKEY or SM change
         */
        if (EHCA_BMASK_GET(NEQE_DISRUPTIVE, eqe)) {
            ehca_warn(&shca->ib_device, "disruptive port "
                  "%d configuration change", port);

            sport->port_state = IB_PORT_DOWN;
            dispatch_port_event(shca, port, IB_EVENT_PORT_ERR,
                        "is inactive");

            sport->port_state = IB_PORT_ACTIVE;
            dispatch_port_event(shca, port, IB_EVENT_PORT_ACTIVE,
                        "is active");
            ehca_query_sma_attr(shca, port,
                        &sport->saved_attr);
        } else
            notify_port_conf_change(shca, port);
        break;
    case 0x32: /* adapter malfunction */
        ehca_err(&shca->ib_device, "Adapter malfunction.");
        break;
    case 0x33:  /* trace stopped */
        ehca_err(&shca->ib_device, "Traced stopped.");
        break;
    case 0x34: /* util async event */
        spec_event = EHCA_BMASK_GET(NEQE_SPECIFIC_EVENT, eqe);
        if (spec_event == 0x80) /* client reregister required */
            dispatch_port_event(shca, port,
                        IB_EVENT_CLIENT_REREGISTER,
                        "client reregister req.");
        else
            ehca_warn(&shca->ib_device, "Unknown util async "
                  "event %x on port %x", spec_event, port);
        break;
    default:
        ehca_err(&shca->ib_device, "Unknown event code: %x on %s.",
             ec, shca->ib_device.name);
        break;
    }

    return;
}

static inline void reset_eq_pending(struct ehca_cq *cq)
{
    u64 CQx_EP;
    struct h_galpa gal = cq->galpas.kernel;

    hipz_galpa_store_cq(gal, cqx_ep, 0x0);
    CQx_EP = hipz_galpa_load(gal, CQTEMM_OFFSET(cqx_ep));

    return;
}

irqreturn_t ehca_interrupt_neq(int irq, void *dev_id)
{
    struct ehca_shca *shca = (struct ehca_shca*)dev_id;

    tasklet_hi_schedule(&shca->neq.interrupt_task);

    return IRQ_HANDLED;
}

void ehca_tasklet_neq(unsigned long data)
{
    struct ehca_shca *shca = (struct ehca_shca*)data;
    struct ehca_eqe *eqe;
    u64 ret;

    eqe = ehca_poll_eq(shca, &shca->neq);

    while (eqe) {
        if (!EHCA_BMASK_GET(NEQE_COMPLETION_EVENT, eqe->entry))
            parse_ec(shca, eqe->entry);

        eqe = ehca_poll_eq(shca, &shca->neq);
    }

    ret = hipz_h_reset_event(shca->ipz_hca_handle,
                 shca->neq.ipz_eq_handle, 0xFFFFFFFFFFFFFFFFL);

    if (ret != H_SUCCESS)
        ehca_err(&shca->ib_device, "Can't clear notification events.");

    return;
}

irqreturn_t ehca_interrupt_eq(int irq, void *dev_id)
{
    struct ehca_shca *shca = (struct ehca_shca*)dev_id;

    tasklet_hi_schedule(&shca->eq.interrupt_task);

    return IRQ_HANDLED;
}


static inline void process_eqe(struct ehca_shca *shca, struct ehca_eqe *eqe)
{
    u64 eqe_value;
    u32 token;
    struct ehca_cq *cq;

    eqe_value = eqe->entry;
    ehca_dbg(&shca->ib_device, "eqe_value=%llx", eqe_value);
    if (EHCA_BMASK_GET(EQE_COMPLETION_EVENT, eqe_value)) {
        ehca_dbg(&shca->ib_device, "Got completion event");
        token = EHCA_BMASK_GET(EQE_CQ_TOKEN, eqe_value);
        read_lock(&ehca_cq_idr_lock);
        cq = idr_find(&ehca_cq_idr, token);
        if (cq)
            atomic_inc(&cq->nr_events);
        read_unlock(&ehca_cq_idr_lock);
        if (cq == NULL) {
            ehca_err(&shca->ib_device,
                 "Invalid eqe for non-existing cq token=%x",
                 token);
            return;
        }
        reset_eq_pending(cq);
        if (ehca_scaling_code)
            queue_comp_task(cq);
        else {
            comp_event_callback(cq);
            if (atomic_dec_and_test(&cq->nr_events))
                wake_up(&cq->wait_completion);
        }
    } else {
        ehca_dbg(&shca->ib_device, "Got non completion event");
        parse_identifier(shca, eqe_value);
    }
}

void ehca_process_eq(struct ehca_shca *shca, int is_irq)
{
    struct ehca_eq *eq = &shca->eq;
    struct ehca_eqe_cache_entry *eqe_cache = eq->eqe_cache;
    u64 eqe_value, ret;
    int eqe_cnt, i;
    int eq_empty = 0;

    spin_lock(&eq->irq_spinlock);
    if (is_irq) {
        const int max_query_cnt = 100;
        int query_cnt = 0;
        int int_state = 1;
        do {
            int_state = hipz_h_query_int_state(
                shca->ipz_hca_handle, eq->ist);
            query_cnt++;
            iosync();
        } while (int_state && query_cnt < max_query_cnt);
        if (unlikely((query_cnt == max_query_cnt)))
            ehca_dbg(&shca->ib_device, "int_state=%x query_cnt=%x",
                 int_state, query_cnt);
    }

    /* read out all eqes */
    eqe_cnt = 0;
    do {
        u32 token;
        eqe_cache[eqe_cnt].eqe = ehca_poll_eq(shca, eq);
        if (!eqe_cache[eqe_cnt].eqe)
            break;
        eqe_value = eqe_cache[eqe_cnt].eqe->entry;
        if (EHCA_BMASK_GET(EQE_COMPLETION_EVENT, eqe_value)) {
            token = EHCA_BMASK_GET(EQE_CQ_TOKEN, eqe_value);
            read_lock(&ehca_cq_idr_lock);
            eqe_cache[eqe_cnt].cq = idr_find(&ehca_cq_idr, token);
            if (eqe_cache[eqe_cnt].cq)
                atomic_inc(&eqe_cache[eqe_cnt].cq->nr_events);
            read_unlock(&ehca_cq_idr_lock);
            if (!eqe_cache[eqe_cnt].cq) {
                ehca_err(&shca->ib_device,
                     "Invalid eqe for non-existing cq "
                     "token=%x", token);
                continue;
            }
        } else
            eqe_cache[eqe_cnt].cq = NULL;
        eqe_cnt++;
    } while (eqe_cnt < EHCA_EQE_CACHE_SIZE);
    if (!eqe_cnt) {
        if (is_irq)
            ehca_dbg(&shca->ib_device,
                 "No eqe found for irq event");
        goto unlock_irq_spinlock;
    } else if (!is_irq) {
        ret = hipz_h_eoi(eq->ist);
        if (ret != H_SUCCESS)
            ehca_err(&shca->ib_device,
                 "bad return code EOI -rc = %lld\n", ret);
        ehca_dbg(&shca->ib_device, "deadman found %x eqe", eqe_cnt);
    }
    if (unlikely(eqe_cnt == EHCA_EQE_CACHE_SIZE))
        ehca_dbg(&shca->ib_device, "too many eqes for one irq event");
    /* enable irq for new packets */
    for (i = 0; i < eqe_cnt; i++) {
        if (eq->eqe_cache[i].cq)
            reset_eq_pending(eq->eqe_cache[i].cq);
    }
    /* check eq */
    spin_lock(&eq->spinlock);
    eq_empty = (!ipz_eqit_eq_peek_valid(&shca->eq.ipz_queue));
    spin_unlock(&eq->spinlock);
    /* call completion handler for cached eqes */
    for (i = 0; i < eqe_cnt; i++)
        if (eq->eqe_cache[i].cq) {
            if (ehca_scaling_code)
                queue_comp_task(eq->eqe_cache[i].cq);
            else {
                struct ehca_cq *cq = eq->eqe_cache[i].cq;
                comp_event_callback(cq);
                if (atomic_dec_and_test(&cq->nr_events))
                    wake_up(&cq->wait_completion);
            }
        } else {
            ehca_dbg(&shca->ib_device, "Got non completion event");
            parse_identifier(shca, eq->eqe_cache[i].eqe->entry);
        }
    /* poll eq if not empty */
    if (eq_empty)
        goto unlock_irq_spinlock;
    do {
        struct ehca_eqe *eqe;
        eqe = ehca_poll_eq(shca, &shca->eq);
        if (!eqe)
            break;
        process_eqe(shca, eqe);
    } while (1);

unlock_irq_spinlock:
    spin_unlock(&eq->irq_spinlock);
}

void ehca_tasklet_eq(unsigned long data)
{
    ehca_process_eq((struct ehca_shca*)data, 1);
}

static int find_next_online_cpu(struct ehca_comp_pool *pool)
{
    int cpu;
    unsigned long flags;

    WARN_ON_ONCE(!in_interrupt());
    if (ehca_debug_level >= 3)
        ehca_dmp(cpu_online_mask, cpumask_size(), "");

    spin_lock_irqsave(&pool->last_cpu_lock, flags);
    do {
        cpu = cpumask_next(pool->last_cpu, cpu_online_mask);
        if (cpu >= nr_cpu_ids)
            cpu = cpumask_first(cpu_online_mask);
        pool->last_cpu = cpu;
    } while (!per_cpu_ptr(pool->cpu_comp_tasks, cpu)->active);
    spin_unlock_irqrestore(&pool->last_cpu_lock, flags);

    return cpu;
}

static void __queue_comp_task(struct ehca_cq *__cq,
                  struct ehca_cpu_comp_task *cct,
                  struct task_struct *thread)
{
    unsigned long flags;

    spin_lock_irqsave(&cct->task_lock, flags);
    spin_lock(&__cq->task_lock);

    if (__cq->nr_callbacks == 0) {
        __cq->nr_callbacks++;
        list_add_tail(&__cq->entry, &cct->cq_list);
        cct->cq_jobs++;
        wake_up_process(thread);
    } else
        __cq->nr_callbacks++;

    spin_unlock(&__cq->task_lock);
    spin_unlock_irqrestore(&cct->task_lock, flags);
}

static void queue_comp_task(struct ehca_cq *__cq)
{
    int cpu_id;
    struct ehca_cpu_comp_task *cct;
    struct task_struct *thread;
    int cq_jobs;
    unsigned long flags;

    cpu_id = find_next_online_cpu(pool);
    BUG_ON(!cpu_online(cpu_id));

    cct = per_cpu_ptr(pool->cpu_comp_tasks, cpu_id);
    thread = *per_cpu_ptr(pool->cpu_comp_threads, cpu_id);
    BUG_ON(!cct || !thread);

    spin_lock_irqsave(&cct->task_lock, flags);
    cq_jobs = cct->cq_jobs;
    spin_unlock_irqrestore(&cct->task_lock, flags);
    if (cq_jobs > 0) {
        cpu_id = find_next_online_cpu(pool);
        cct = per_cpu_ptr(pool->cpu_comp_tasks, cpu_id);
        thread = *per_cpu_ptr(pool->cpu_comp_threads, cpu_id);
        BUG_ON(!cct || !thread);
    }
    __queue_comp_task(__cq, cct, thread);
}

static void run_comp_task(struct ehca_cpu_comp_task *cct)
{
    struct ehca_cq *cq;

    while (!list_empty(&cct->cq_list)) {
        cq = list_entry(cct->cq_list.next, struct ehca_cq, entry);
        spin_unlock_irq(&cct->task_lock);

        comp_event_callback(cq);
        if (atomic_dec_and_test(&cq->nr_events))
            wake_up(&cq->wait_completion);

        spin_lock_irq(&cct->task_lock);
        spin_lock(&cq->task_lock);
        cq->nr_callbacks--;
        if (!cq->nr_callbacks) {
            list_del_init(cct->cq_list.next);
            cct->cq_jobs--;
        }
        spin_unlock(&cq->task_lock);
    }
}

static void comp_task_park(unsigned int cpu)
{
    struct ehca_cpu_comp_task *cct = per_cpu_ptr(pool->cpu_comp_tasks, cpu);
    struct ehca_cpu_comp_task *target;
    struct task_struct *thread;
    struct ehca_cq *cq, *tmp;
    LIST_HEAD(list);

    spin_lock_irq(&cct->task_lock);
    cct->cq_jobs = 0;
    cct->active = 0;
    list_splice_init(&cct->cq_list, &list);
    spin_unlock_irq(&cct->task_lock);

    cpu = find_next_online_cpu(pool);
    target = per_cpu_ptr(pool->cpu_comp_tasks, cpu);
    thread = *per_cpu_ptr(pool->cpu_comp_threads, cpu);
    spin_lock_irq(&target->task_lock);
    list_for_each_entry_safe(cq, tmp, &list, entry) {
        list_del(&cq->entry);
        __queue_comp_task(cq, target, thread);
    }
    spin_unlock_irq(&target->task_lock);
}

static void comp_task_stop(unsigned int cpu, bool online)
{
    struct ehca_cpu_comp_task *cct = per_cpu_ptr(pool->cpu_comp_tasks, cpu);

    spin_lock_irq(&cct->task_lock);
    cct->cq_jobs = 0;
    cct->active = 0;
    WARN_ON(!list_empty(&cct->cq_list));
    spin_unlock_irq(&cct->task_lock);
}

static int comp_task_should_run(unsigned int cpu)
{
    struct ehca_cpu_comp_task *cct = per_cpu_ptr(pool->cpu_comp_tasks, cpu);

    return cct->cq_jobs;
}

static void comp_task(unsigned int cpu)
{
    struct ehca_cpu_comp_task *cct = this_cpu_ptr(pool->cpu_comp_tasks);
    int cql_empty;

    spin_lock_irq(&cct->task_lock);
    cql_empty = list_empty(&cct->cq_list);
    if (!cql_empty) {
        __set_current_state(TASK_RUNNING);
        run_comp_task(cct);
    }
    spin_unlock_irq(&cct->task_lock);
}

static struct smp_hotplug_thread comp_pool_threads = {
    .thread_should_run  = comp_task_should_run,
    .thread_fn      = comp_task,
    .thread_comm        = "ehca_comp/%u",
    .cleanup        = comp_task_stop,
    .park           = comp_task_park,
};

int ehca_create_comp_pool(void)
{
    int cpu, ret = -ENOMEM;

    if (!ehca_scaling_code)
        return 0;

    pool = kzalloc(sizeof(struct ehca_comp_pool), GFP_KERNEL);
    if (pool == NULL)
        return -ENOMEM;

    spin_lock_init(&pool->last_cpu_lock);
    pool->last_cpu = cpumask_any(cpu_online_mask);

    pool->cpu_comp_tasks = alloc_percpu(struct ehca_cpu_comp_task);
    if (!pool->cpu_comp_tasks)
        goto out_pool;

    pool->cpu_comp_threads = alloc_percpu(struct task_struct *);
    if (!pool->cpu_comp_threads)
        goto out_tasks;

    for_each_present_cpu(cpu) {
        struct ehca_cpu_comp_task *cct;

        cct = per_cpu_ptr(pool->cpu_comp_tasks, cpu);
        spin_lock_init(&cct->task_lock);
        INIT_LIST_HEAD(&cct->cq_list);
    }

    comp_pool_threads.store = pool->cpu_comp_threads;
    ret = smpboot_register_percpu_thread(&comp_pool_threads);
    if (ret)
        goto out_threads;

    pr_info("eHCA scaling code enabled\n");
    return ret;

out_threads:
    free_percpu(pool->cpu_comp_threads);
out_tasks:
    free_percpu(pool->cpu_comp_tasks);
out_pool:
    kfree(pool);
    return ret;
}

void ehca_destroy_comp_pool(void)
{
    if (!ehca_scaling_code)
        return;

    smpboot_unregister_percpu_thread(&comp_pool_threads);

    free_percpu(pool->cpu_comp_threads);
    free_percpu(pool->cpu_comp_tasks);
    kfree(pool);
}