linux-kernel - Re: [patch 1/2] spufs: make dentry reference count and locking symmetric

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Message-Id: <200905121603.50251.ARNDB@de.ibm.com>
Date:	Tue, 12 May 2009 16:03:49 +0200
From:	Arnd Bergmann <ARNDB@...ibm.com>
To:	jblunck@...e.de
Cc:	Linux-Kernel Mailinglist <linux-kernel@...r.kernel.org>,
	Jeremy Kerr <jk@...abs.org>
Subject: Re: [patch 1/2] spufs: make dentry reference count and locking symmetric

On Tuesday 05 May 2009, jblunck@...e.de wrote:
> @@ -505,10 +505,7 @@ spufs_create_context(struct inode *inode
>  out_aff_unlock:
>         if (affinity)
>                 mutex_unlock(&gang->aff_mutex);
> -out_unlock:
> -       mutex_unlock(&inode->i_mutex);
>  out:
> -       dput(dentry);
>         return ret;
>  }
>  

There is a nasty deadlock problem with spu_forget(), which we
must call after unlocking i_mutex but before the final dput, IIRC.

The path down there is something like 

spu_forget -> mmput -> exit_mmap -> remove_vma -> 
	fput -> dput -> dentry_iput -> iput -> iput_final ->
	spufs_delete_inode -> destroy_spu_context.

	Arnd <><
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