linux-kernel - Re: [patch 1/3] fastboot: Create a "asynchronous" initlevel

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Message-ID: <20080719084448.7859afd0@infradead.org>
Date:	Sat, 19 Jul 2008 08:44:48 -0700
From:	Arjan van de Ven <arjan@...radead.org>
To:	Rene Herman <rene.herman@...access.nl>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu
Subject: Re: [patch 1/3] fastboot: Create a "asynchronous" initlevel

On Sat, 19 Jul 2008 10:10:09 +0200
Rene Herman <rene.herman@...access.nl> wrote:

> On 19-07-08 09:53, Rene Herman wrote:
> > On 19-07-08 00:16, Arjan van de Ven wrote:
> > 
> >> +static void __init do_initcalls(void)
> >> +{
> >> +    initcall_t *call;
> >> +    static DECLARE_WORK(async_work, do_async_initcalls);
> >> +    int phase = 0; /* 0 = levels 0 - 6, 1 = level 6a, 2 = after
> >> level 6a */
> >> +
> >> +    async_init_wq = create_singlethread_workqueue("kasyncinit");
> >> +
> >> +    for (call = __initcall_start; call < __initcall_end; call++) {
> >> +        if (phase == 0 && call >= __async_initcall_start) {
> >> +            phase = 1;
> >> +            queue_work(async_init_wq, &async_work);
> >> +        }
> >> +        if (phase == 1 && call >= __async_initcall_end)
> >> +            phase = 2;
> >> +        if (phase != 1)
> >> +            do_one_initcall(*call);
> >> +    }
> > 
> > I'm not sure about this comment, being not very sure about the
> > semantics of late_initcall but shouldn't late_initcall (level 7)
> > wait for 6s to have completed?
> 
> Following up on this myself -- see for example kernel/power/disk.c: 
> power_suspend(). It's a late intitcall so that, as it comments, "all 
> devices are discovered and initialized". However, your first followup 
> patch makes the USB HCI init async meaning that any USB storage
> device might not be ready yet when it runs, no?


good spotting/comment.

you would have a valid point... if it weren't for the case where much
of this actual "end device" probing is in various cases already
asynchronous... what you do have found is a bug in the suspend code.
Unless code does:
        /* wait for the known devices to complete their probing */
        while (driver_probe_done() != 0)
                msleep(100);
(taken from init/do_mounts.c)

... the assertion in the comment that probing is done is absolutely
false, with or without my patches.

(Not that I want the suspend/resume code to call this, because that
would make the boot even longer ;( )


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