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    SubjectRe: [PATCH 2/2] scsi: don't use execute_in_process_context()
    On 12/15/2010 08:19 PM, Tejun Heo wrote:
    > Given that the structures containing the work items are dynamically
    > allocated, I would introduce a scsi_wq, unconditionally schedule
    > release works on them and flush them before unloading. Please note
    > that workqueues no longer require dedicated threads, so it's quite
    > cheap.

    So, something like the following.

    ---
    drivers/scsi/scsi.c | 15 +++++++++++++--
    drivers/scsi/scsi_scan.c | 26 +++++++++++++-------------
    drivers/scsi/scsi_sysfs.c | 8 +++++---
    include/scsi/scsi_device.h | 6 ++++--
    4 files changed, 35 insertions(+), 20 deletions(-)

    Index: work/drivers/scsi/scsi_scan.c
    ===================================================================
    --- work.orig/drivers/scsi/scsi_scan.c
    +++ work/drivers/scsi/scsi_scan.c
    @@ -362,6 +362,16 @@ int scsi_is_target_device(const struct d
    }
    EXPORT_SYMBOL(scsi_is_target_device);

    +static void scsi_target_reap_usercontext(struct work_struct *work)
    +{
    + struct scsi_target *starget =
    + container_of(work, struct scsi_target, reap_work);
    +
    + transport_remove_device(&starget->dev);
    + device_del(&starget->dev);
    + scsi_target_destroy(starget);
    +}
    +
    static struct scsi_target *__scsi_find_target(struct device *parent,
    int channel, uint id)
    {
    @@ -427,6 +437,7 @@ static struct scsi_target *scsi_alloc_ta
    starget->state = STARGET_CREATED;
    starget->scsi_level = SCSI_2;
    starget->max_target_blocked = SCSI_DEFAULT_TARGET_BLOCKED;
    + INIT_WORK(&starget->reap_work, scsi_target_reap_usercontext);
    retry:
    spin_lock_irqsave(shost->host_lock, flags);

    @@ -462,21 +473,11 @@ static struct scsi_target *scsi_alloc_ta
    }
    /* Unfortunately, we found a dying target; need to
    * wait until it's dead before we can get a new one */
    + flush_work(&found_target->reap_work);
    put_device(&found_target->dev);
    - flush_scheduled_work();
    goto retry;
    }

    -static void scsi_target_reap_usercontext(struct work_struct *work)
    -{
    - struct scsi_target *starget =
    - container_of(work, struct scsi_target, ew.work);
    -
    - transport_remove_device(&starget->dev);
    - device_del(&starget->dev);
    - scsi_target_destroy(starget);
    -}
    -
    /**
    * scsi_target_reap - check to see if target is in use and destroy if not
    * @starget: target to be checked
    @@ -507,8 +508,7 @@ void scsi_target_reap(struct scsi_target
    if (state == STARGET_CREATED)
    scsi_target_destroy(starget);
    else
    - execute_in_process_context(scsi_target_reap_usercontext,
    - &starget->ew);
    + queue_work(scsi_wq, &starget->reap_work);
    }

    /**
    Index: work/drivers/scsi/scsi_sysfs.c
    ===================================================================
    --- work.orig/drivers/scsi/scsi_sysfs.c
    +++ work/drivers/scsi/scsi_sysfs.c
    @@ -300,7 +300,7 @@ static void scsi_device_dev_release_user
    struct list_head *this, *tmp;
    unsigned long flags;

    - sdev = container_of(work, struct scsi_device, ew.work);
    + sdev = container_of(work, struct scsi_device, release_work);

    parent = sdev->sdev_gendev.parent;
    starget = to_scsi_target(parent);
    @@ -343,8 +343,8 @@ static void scsi_device_dev_release_user
    static void scsi_device_dev_release(struct device *dev)
    {
    struct scsi_device *sdp = to_scsi_device(dev);
    - execute_in_process_context(scsi_device_dev_release_usercontext,
    - &sdp->ew);
    +
    + queue_work(scsi_wq, &sdp->release_work);
    }

    static struct class sdev_class = {
    @@ -1069,6 +1069,8 @@ void scsi_sysfs_device_initialize(struct
    dev_set_name(&sdev->sdev_dev, "%d:%d:%d:%d",
    sdev->host->host_no, sdev->channel, sdev->id, sdev->lun);
    sdev->scsi_level = starget->scsi_level;
    + INIT_WORK(&sdev->release_work, scsi_device_dev_release_usercontext);
    +
    transport_setup_device(&sdev->sdev_gendev);
    spin_lock_irqsave(shost->host_lock, flags);
    list_add_tail(&sdev->same_target_siblings, &starget->devices);
    Index: work/include/scsi/scsi_device.h
    ===================================================================
    --- work.orig/include/scsi/scsi_device.h
    +++ work/include/scsi/scsi_device.h
    @@ -168,7 +168,7 @@ struct scsi_device {
    struct device sdev_gendev,
    sdev_dev;

    - struct execute_work ew; /* used to get process context on put */
    + struct work_struct release_work; /* for process context on put */

    struct scsi_dh_data *scsi_dh_data;
    enum scsi_device_state sdev_state;
    @@ -258,7 +258,7 @@ struct scsi_target {
    #define SCSI_DEFAULT_TARGET_BLOCKED 3

    char scsi_level;
    - struct execute_work ew;
    + struct work_struct reap_work;
    enum scsi_target_state state;
    void *hostdata; /* available to low-level driver */
    unsigned long starget_data[0]; /* for the transport */
    @@ -276,6 +276,8 @@ static inline struct scsi_target *scsi_t
    #define starget_printk(prefix, starget, fmt, a...) \
    dev_printk(prefix, &(starget)->dev, fmt, ##a)

    +extern struct workqueue_struct *scsi_wq;
    +
    extern struct scsi_device *__scsi_add_device(struct Scsi_Host *,
    uint, uint, uint, void *hostdata);
    extern int scsi_add_device(struct Scsi_Host *host, uint channel,
    Index: work/drivers/scsi/scsi.c
    ===================================================================
    --- work.orig/drivers/scsi/scsi.c
    +++ work/drivers/scsi/scsi.c
    @@ -70,6 +70,11 @@
    #define CREATE_TRACE_POINTS
    #include <trace/events/scsi.h>

    +/*
    + * Utility multithreaded workqueue for SCSI.
    + */
    +struct workqueue_struct *scsi_wq;
    +
    static void scsi_done(struct scsi_cmnd *cmd);

    /*
    @@ -1306,11 +1311,14 @@ MODULE_PARM_DESC(scsi_logging_level, "a

    static int __init init_scsi(void)
    {
    - int error;
    + int error = -ENOMEM;

    + scsi_wq = alloc_workqueue("scsi", 0, 0);
    + if (!scsi_wq)
    + return error;
    error = scsi_init_queue();
    if (error)
    - return error;
    + goto cleanup_wq;
    error = scsi_init_procfs();
    if (error)
    goto cleanup_queue;
    @@ -1342,6 +1350,8 @@ cleanup_procfs:
    scsi_exit_procfs();
    cleanup_queue:
    scsi_exit_queue();
    +cleanup_wq:
    + destroy_workqueue(scsi_wq);
    printk(KERN_ERR "SCSI subsystem failed to initialize, error = %d\n",
    -error);
    return error;
    @@ -1356,6 +1366,7 @@ static void __exit exit_scsi(void)
    scsi_exit_devinfo();
    scsi_exit_procfs();
    scsi_exit_queue();
    + destroy_workqueue(scsi_wq);
    }

    subsys_initcall(init_scsi);

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