linux-kernel - Re: [linux-pm] [2.6.30-rc1-git2 regressions] Hibernation broken and (minor but annoying) audio problem

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Message-Id: <200904110206.33525.rjw@suse.com>
Date:	Sat, 11 Apr 2009 02:06:32 +0200
From:	"Rafael J. Wysocki" <rjw@...e.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	linux-pm@...ts.linux-foundation.org, Takashi Iwai <tiwai@...e.de>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [linux-pm] [2.6.30-rc1-git2 regressions] Hibernation broken and (minor but annoying) audio problem

[Sorry for having to switch the From address, my MTA has just decided to break.]

On Friday 10 April 2009, Linus Torvalds wrote:
> 
> On Fri, 10 Apr 2009, Rafael J. Wysocki wrote:
> > 
> > I've just verified that the resume-after-hibernation issue goes away after
> > reverting commit 9710794383ee5008d67f1a6613a4717bf6de47bc
> > (async: remove the temporary (2.6.29) "async is off by default" code) , so it
> > is async-related.
> 
> Arjan? Clearly all the necessary fixes weren't found..
> 
> There _is_ a module loading problem wrt initmem - I think you found that 
> and we added a hack for it for the ACPI battery driver. I wonder if we're 
> hitting a similar issue now with module discovery: modules that use 
> "async_schedule()" to do their discovery asynchronously are now not 
> necessarily fully "done" when the module is loaded. 
> 
> And so, anything that expected the devices to be available after module 
> load (like they used to) would be screwed.
> 
> IOW, maybe something like the totally untested patch appended here (that 
> should also allow us to make the ACPI battery code to go back to using 
> __init).

I tested it and it worked.

> As usual, I'm not using modules, so what do I know.
> 
> > The audio issue still remains after the revert, so it is really different.
> 
> Ok, probably something from Takashi..

This one is only reproducible in one out of three attempts on the average.
I tried to bisect, but it went to nowhere.

Thanks,
Rafael

 
> ---
>  kernel/module.c |    3 +++
>  1 files changed, 3 insertions(+), 0 deletions(-)
> 
> diff --git a/kernel/module.c b/kernel/module.c
> index 05f014e..e797812 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -2388,6 +2388,9 @@ SYSCALL_DEFINE3(init_module, void __user *, umod,
>  	blocking_notifier_call_chain(&module_notify_list,
>  				     MODULE_STATE_LIVE, mod);
>  
> +	/* We need to finish all async code before the module init sequence is done */
> +	async_synchronize_full();
> +
>  	mutex_lock(&module_mutex);
>  	/* Drop initial reference. */
>  	module_put(mod);
> 
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