linux-kernel - Re: uart_startup: GFP_KERNEL allocation with IRQs disabled

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Message-ID: <501B9BF1.2050006@suse.cz>
Date:	Fri, 03 Aug 2012 11:37:53 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	Fengguang Wu <fengguang.wu@...el.com>
CC:	Alan Cox <alan@...ux.intel.com>, Al Viro <viro@...iv.linux.org.uk>,
	LKML <linux-kernel@...r.kernel.org>,
	Greg KH <gregkh@...uxfoundation.org>
Subject: Re: uart_startup: GFP_KERNEL allocation with IRQs disabled

On 08/03/2012 03:46 AM, Fengguang Wu wrote:
> Hi all,

Hi,

> The IRQ should be disabled somewhere in the path walk, which makes
> the GFP_KERNEL allocation in uart_startup() no longer valid..
> 
> [    0.499537] kworker/u:1 (29) used greatest stack depth: 7156 bytes left
> [    0.500947] ------------[ cut here ]------------
> [    0.501445] WARNING: at /c/kernel-tests/src/stable/kernel/lockdep.c:2739 lockdep_trace_alloc+0x86/0xb2()
> [    0.502413] Modules linked in:
> [    0.502766] Pid: 1, comm: init Not tainted 3.5.0-01258-g1ade992 #182
> [    0.503419] Call Trace:
...
> [    0.504381]  [<c1079e7d>] get_zeroed_page+0xd/0xf
> [    0.504381]  [<c10f976f>] uart_startup.part.8+0x46/0x152
> [    0.504381]  [<c10f745f>] ? tty_port_tty_set+0x37/0x3c
> [    0.504381]  [<c10fa175>] uart_open+0xc9/0x10b
> [    0.504381]  [<c10fa0ac>] ? uart_suspend_port+0x229/0x229
> [    0.504381]  [<c10f1bc2>] tty_open+0x26b/0x3d3
> [    0.504381]  [<c109872a>] chrdev_open+0xf7/0x117

This does not make sense to me. I would not blame TTY/serial for this.
There is somebody who forgot to enable interrupts somewhere. Could you
enable DEBUG_ATOMIC_SLEEP? It might trigger earlier revealing us the
culprit.

thanks,
-- 
js
suse labs
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