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    SubjectRe: [PATCH 2/2] firmware_class: Move request_firmware_nowait() to workqueues
    On 03/27/12 15:55, Rafael J. Wysocki wrote:
    > On Wednesday, March 28, 2012, Tejun Heo wrote:
    >> On Wed, Mar 28, 2012 at 12:21:27AM +0200, Rafael J. Wysocki wrote:
    >>> On Wednesday, March 28, 2012, Tejun Heo wrote:
    >>>> On Tue, Mar 27, 2012 at 02:28:30PM -0700, Stephen Boyd wrote:
    >>>>> Oddly enough a work_struct was already part of the firmware_work
    >>>>> structure but nobody was using it. Instead of creating a new
    >>>>> kthread for each request_firmware_nowait() call just schedule the
    >>>>> work on the long system workqueue. This should avoid some overhead
    >>>>> in forking new threads when they're not strictly necessary.
    >>>>>
    >>>>> Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
    >>>>> ---
    >>>>>
    >>>>> Is it better to use alloc_workqueue() and not put these on the system
    >>>>> long workqueue?
    >>>> No, just use schedule_work() unless there are specific requirements
    >>>> which can't be fulfilled that way (e.g. it's on memory allocation
    >>>> path, may consume large amount of cpu cycles, ...)
    >>> It may wait quite long.
    >> That shouldn't matter. system_long_wq's name is a bit misleading at
    >> this point. The only reason it's used currently is to avoid cyclic
    >> dependency involving flush_workqueue(), which calls for clearer
    >> solution anyway. So, yeap, using system_wq should be fine here.
    > Good, thanks for the explanation.
    >
    > Stephen, care to respin?
    >

    Sure. We want system_wq instead of system_long_wq? If so let's use this
    patch.

    -----8<-- cut here -->8------

    Subject: [PATCH] firmware_class: Move request_firmware_nowait() to workqueues

    Oddly enough a work_struct was already part of the firmware_work
    structure but nobody was using it. Instead of creating a new
    kthread for each request_firmware_nowait() call just schedule the
    work on the system workqueue. This should avoid some overhead
    in forking new threads when they're not strictly necessary.

    Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
    ---
    drivers/base/firmware_class.c | 27 +++++++--------------------
    1 file changed, 7 insertions(+), 20 deletions(-)

    diff --git a/drivers/base/firmware_class.c b/drivers/base/firmware_class.c
    index ae00a2f..5401814 100644
    --- a/drivers/base/firmware_class.c
    +++ b/drivers/base/firmware_class.c
    @@ -16,10 +16,11 @@
    #include <linux/interrupt.h>
    #include <linux/bitops.h>
    #include <linux/mutex.h>
    -#include <linux/kthread.h>
    +#include <linux/workqueue.h>
    #include <linux/highmem.h>
    #include <linux/firmware.h>
    #include <linux/slab.h>
    +#include <linux/sched.h>

    #define to_dev(obj) container_of(obj, struct device, kobj)

    @@ -630,19 +631,15 @@ struct firmware_work {
    bool uevent;
    };

    -static int request_firmware_work_func(void *arg)
    +static void request_firmware_work_func(struct work_struct *work)
    {
    - struct firmware_work *fw_work = arg;
    + struct firmware_work *fw_work;
    const struct firmware *fw;
    struct firmware_priv *fw_priv;
    long timeout;
    int ret;

    - if (!arg) {
    - WARN_ON(1);
    - return 0;
    - }
    -
    + fw_work = container_of(work, struct firmware_work, work);
    fw_priv = _request_firmware_prepare(&fw, fw_work->name, fw_work->device,
    fw_work->uevent, true);
    if (IS_ERR_OR_NULL(fw_priv)) {
    @@ -667,8 +664,6 @@ static int request_firmware_work_func(void *arg)

    module_put(fw_work->module);
    kfree(fw_work);
    -
    - return ret;
    }

    /**
    @@ -694,7 +689,6 @@ request_firmware_nowait(
    const char *name, struct device *device, gfp_t gfp, void *context,
    void (*cont)(const struct firmware *fw, void *context))
    {
    - struct task_struct *task;
    struct firmware_work *fw_work;

    fw_work = kzalloc(sizeof (struct firmware_work), gfp);
    @@ -713,15 +707,8 @@ request_firmware_nowait(
    return -EFAULT;
    }

    - task = kthread_run(request_firmware_work_func, fw_work,
    - "firmware/%s", name);
    - if (IS_ERR(task)) {
    - fw_work->cont(NULL, fw_work->context);
    - module_put(fw_work->module);
    - kfree(fw_work);
    - return PTR_ERR(task);
    - }
    -
    + INIT_WORK(&fw_work->work, request_firmware_work_func);
    + schedule_work(&fw_work->work);
    return 0;
    }

    --
    Sent by an employee of the Qualcomm Innovation Center, Inc.
    The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.



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