linux-kernel - Re: [PATCH 2/2] module: fix bne2 "gave up waiting for init of module libcrc32c"

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Message-Id: <201006011449.51587.rusty@rustcorp.com.au>
Date:	Tue, 1 Jun 2010 14:49:50 +0930
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Brandon Philips <brandon@...p.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	LKML <linux-kernel@...r.kernel.org>,
	Jon Masters <jonathan@...masters.org>,
	Tejun Heo <htejun@...il.com>,
	Masami Hiramatsu <mhiramat@...hat.com>,
	Kay Sievers <kay.sievers@...y.org>
Subject: Re: [PATCH 2/2] module: fix bne2 "gave up waiting for init of module libcrc32c"

On Tue, 1 Jun 2010 01:10:36 pm Linus Torvalds wrote:
> 
> On Tue, 1 Jun 2010, Rusty Russell wrote:
> 
> > On Tue, 1 Jun 2010 05:45:37 am Linus Torvalds wrote:
> > > 
> > > basically, we should do the whole module dependency list regardless 
> > > of whether we can unload modules or not 
> > 
> > Why?
> 
> Because the current non-CONFIG_MODULE_UNLOAD code is currently broken, and 
> it was broken exactly because the code had two totally different paths and 
> totally different logic. And one part simply missed the case.
> 
> We'd be much better off having as much of the logic shared as possible. 
> No?
> 
> Your 2/2 actually fixed that, because it moved the broken 
> wait_event_interruptible_timeout() out of the (non-shared) use_module() 
> into the (shared) resolve_symbol_wait(). But even that seemed to be almost 
> accidental, and seemed to be more about the fact that now the locking 
> rules required it (if you wanted to wait without holding the lock), rather 
> than anything else.

!CONFIG_MODULE_UNLOAD still does the old "fail don't wait" behavior.

So yes, moving the waiting into common code was a win for consistency,
either with your patch or mine.

> So I'd suggest we should just track those module dependencies, and share 
> more of the code and the logic. Because it looks to me like not sharing it 
> continually results in bugs.
> 
> No?

I wonder if we should just get rid of !CONFIG_UNLOAD then?  I have a soft spot
for it because it keeps us honest and shows how much shit is there simply for
our poor man's pagable kernel.

Let me compile up a kernel with and without and see what it's really doing
to us...

Thanks,
Rusty.
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