linux-kernel - Re: [Regression] Crash in load

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Message-ID: <20100527184602.GF7351@jenkins.ifup.org>
Date:	Thu, 27 May 2010 11:46:02 -0700
From:	Brandon Philips <brandon@...p.org>
To:	Rusty Russell <rusty@...tcorp.com.au>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jon Masters <jonathan@...masters.org>,
	Tejun Heo <htejun@...il.com>,
	Masami Hiramatsu <mhiramat@...hat.com>
Subject: Re: [Regression] Crash in load_module() while freeing args

On 14:56 Thu 27 May 2010, Rusty Russell wrote:
> On Thu, 27 May 2010 08:26:25 am Rafael J. Wysocki wrote:
> > On Wednesday 26 May 2010, Rusty Russell wrote:
> > > I suspect that the increased parallelism enabled by this patch uncovered this
> > > bug.  Does this fix it?
> > 
> > Since the commit has been reverted, do you still want me to test this patch?
> > Quite frankly I'd prefer to test a complete replacement for that commit on top
> > of current -git.
> 
> OK, combo meal deal below, against Linus' latest.  I'd really appreciate
> a report, since AFAIK you're the only one hitting it, and only when that
> other (now reverted) patch was applied.

I tested this patch on my machine on top of Linus's latest and it
fixes the issue. Without the patch and using Linus's latest I
reproduce the original issue:

[   60.836022] bnx2: gave up waiting for init of module libcrc32c.
[   60.847997] bnx2: Unknown symbol crc32c

Note: Again, since I don't have bnx2x hardware I forced bnx2.ko to
depend on libcrc32c as bnx2x does:
  http://ifup.org/~philips/review/bnx2-hack-to-use-libcrc32c.patch

> As an side to Brandon: I can see how my patch fixed an explicit
> request_module inside module_init (that's how I tested it).  I can't
> see how we have a problem with an implicit dependency such as
> bne2x->crc32.  Modules go into the live state without retaking the
> lock.

libcrc32c is doing an explicit request_module inside of its
module_init. Follow the call chain in libcrc32c_mod_init()

libcrc32c_mod_init
 crypto_alloc_shash
  crypto_alloc_tfm
   crypto_find_alg
    crypto_alg_mod_lookup
     crypto_larval_lookup
      request_module

Cheers,

	Brandon
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