Messages in this thread | | | Date | Sun, 18 Mar 2012 01:26:41 -0700 | From | Stephen Boyd <> | Subject | Re: [PATCH] firmware loader: don't cancel _nowait requests when helper is not yet available |
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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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