linux-kernel - Re: [PATCH][Resend v2] Fix infinite loop in search_binary

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Date:	Tue, 5 Jul 2011 00:17:29 +0200
From:	Richard Weinberger <richard@....at>
To:	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Cc:	viro@...iv.linux.org.uk, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH][Resend v2] Fix infinite loop in search_binary_handler()

Am Dienstag 05 Juli 2011, 00:03:47 schrieb Tetsuo Handa:
> Richard Weinberger wrote:
> > Am Montag 04 Juli 2011, 16:59:32 schrieb Richard Weinberger:
> > > Here the second boot log:
> > > http://userweb.kernel.org/~rw/boot2.log
> > > 
> > > The interesting part is:
> > > ---cut---
> > > VFS: Mounted root (ext2 filesystem) readonly on device 98:0.
> > > Calling request_module() swapper 1 /sbin/init 1 3
> > > Calling request_module() kworker/u:0 211 /sbin/modprobe 4 3
> > > ...
> > > Calling request_module() kworker/u:0 8741 /sbin/modprobe 4 3
> > > ---cut---
> > > 
> > > After the last "Calling request_module..." message no more messages
> > > appear and the kernel seems to loop for ever.
> > 
> > Please ignore this.
> > The "Calling request_module..." messages continue for ever.
> > In the first case my terminal locked up...
> > current->pid also wraps around.
> 
> Please note that the each PID is printed for twice.
> This means that each thread within the loop tries to create a thread.
> Therefore, it will repeat for (1 << MAX_KMOD_CONCURRENT) times.
> It is large enough to wrap the PID.
> Well, try with smaller MAX_KMOD_CONCURRENT (e.g. 3).
> 

With MAX_KMOD_CONCURRENT=3 it takes only a few seconds until 
the modprobe storm ends.

How shall we proceed?
Applying my ad-hoc patch 
or lowering MAX_KMOD_CONCURRENT?

Thanks,
//richard
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