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    SubjectRe: [PATCH] firmware loader: don't cancel _nowait requests when helper is not yet available
    On 3/16/2012 10:51 PM, Linus Torvalds wrote:
    > On Fri, Mar 16, 2012 at 7:47 PM, Stephen Boyd <sboyd@codeaurora.org> wrote:
    >> - if (WARN_ON(usermodehelper_is_disabled())) {
    >> + if (is_sleep_task()) {
    >> dev_err(device, "firmware: %s will not be loaded\n", name);
    > Stop these idiotic games already!
    >
    > It's very simple: you cannot load firmware while the system is not
    > readt. Your moronic "let's change the test to something else" is
    > entirely and utterly misguided and totally misses the point.
    >
    > It's not about sleeping, and it's not about anything even *remotely*
    > about that. Stop the idiocy already.
    >
    > How hard is it to understand? How many times do people have to tell you?
    >
    > That warning is very much valid during bootup, and that warning has
    > been *seen* during bootup. For example, try to compile in most
    > wireless drivers as non-modular, and that warning *has* to trigger.

    Ok. I like where nowait() is going in the other part of the thread but
    I'm still confused about when request_firmware() is correct to use. It
    seems that the function is inherently racy with freezing. Does every
    user of request_firmware() need to synchronize with freezing?

    For example, if one CPU is in the middle of a driver probe that makes a
    request_firmware() call and another CPU is starting to suspend we will
    have a race between usermodehelpers being disabled and the
    request_firmware() call acquiring the usermodehelper rwsem. If the
    suspending CPU wins the race it will disable usermodehelpers and the
    request_firmware() call will return -EBUSY and warn.

    CPU0 CPU1
    driver_probe() suspend_prepare()
    ... usermodehelper_disable()
    _request_firmware() down_write(&umhelper_sem)
    usermodehelper_disabled = 1
    up_write(&umhelper_sem)
    down_read(&umhelper_sem) ....
    WARN_ON(...) freeze_processes()
    <freeze>


    Hopefully I'm missing something here? This is all theoretical right now
    as I haven't actually seen any of this in practice.

    --
    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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