linux-kernel - Re: [PATCH] fs/proc: Move kfree outside pde_unload

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Date:	Wed, 29 Aug 2012 11:32:26 +0300
From:	Alexey Dobriyan <adobriyan@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Nathan Zimmer <nzimmer@....com>, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org,
	Alexander Viro <viro@...iv.linux.org.uk>,
	David Woodhouse <dwmw2@...radead.org>
Subject: Re: [PATCH] fs/proc: Move kfree outside pde_unload_lock

On Tue, Aug 28, 2012 at 09:11:57PM -0700, Eric Dumazet wrote:
> On Tue, 2012-08-28 at 23:38 +0300, Alexey Dobriyan wrote:
> 
> > Nothing can stop RCU!
> > 
> > After running "modprobe;rmmod" in a loop and "cat" in another loop for a while
> > rmmod got stuck in D-state inside remove_proc_entry() with trace amounts of CPU time
> > being consumed.
> > 
> > It didn't oopsed, though.
> 
> Thanks ! 
> 
> I'll polish this patch once LKS/LPC is over...
> 
> What particular module and/or proc file did you use for your tests ?

Just dummy one.

#include <linux/init.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>

static int foo_proc_show(struct seq_file *m, void *v)
{
	seq_puts(m, "foo\n");
	return 0;
}

static int foo_proc_open(struct inode *inode, struct file *file)
{
	return single_open(file, foo_proc_show, NULL);
}

static const struct file_operations foo_proc_ops = {
	.open	= foo_proc_open,
	.read	= seq_read,
	.llseek	= seq_lseek,
	.release = single_release,
};

static int __init foo_module_init(void)
{
	proc_create("foo", 0, NULL, &foo_proc_ops);
	return 0;
}

static void __exit foo_module_exit(void)
{
	remove_proc_entry("foo", NULL);
}
module_init(foo_module_init);
module_exit(foo_module_exit);
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