linux-kernel - Re: [PATCH] atmel_serial: fix spinlock lockup in RS485 code

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Message-ID: <20111215185814.GD18791@kroah.com>
Date:	Thu, 15 Dec 2011 10:58:14 -0800
From:	Greg KH <greg@...ah.com>
To:	Claudio Scordino <claudio@...dence.eu.com>
Cc:	Alan Cox <alan@...ux.intel.com>,
	Nicolas Ferre <nicolas.ferre@...el.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	"linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
	Dave Bender <codehero@...il.com>
Subject: Re: [PATCH] atmel_serial: fix spinlock lockup in RS485 code

On Thu, Dec 15, 2011 at 12:04:42PM +0100, Claudio Scordino wrote:
> Il 15/12/2011 11:00, Nicolas Ferre ha scritto:
> >On 12/15/2011 09:47 AM, Claudio Scordino :
> >>Hi all.
> >>
> >>We have encountered a spinlock lockup in the RS485 part of the
> >>atmel_serial driver.
> >>
> >>Here is the trace:
> >>
> >>[   68.030000] BUG: spinlock lockup on CPU#0, dnp_master/244, c07e82c0
> >>[   68.040000] [<c002a790>] (unwind_backtrace+0x0/0xf0) from
> >>[<c012f8f0>] (do_raw_spin_lock+0x10c/0x148)
> >>[   68.050000] [<c012f8f0>] (do_raw_spin_lock+0x10c/0x148) from
> >>[<c015152c>] (atmel_tasklet_func+0x10/0x708)
> >>[   68.060000] [<c015152c>] (atmel_tasklet_func+0x10/0x708) from
> >>[<c003bfd4>] (tasklet_action+0x8c/0xf4)
> >>[   68.070000] [<c003bfd4>] (tasklet_action+0x8c/0xf4) from [<c003c630>]
> >>(__do_softirq+0xa4/0x180)
> >>[   68.080000] [<c003c630>] (__do_softirq+0xa4/0x180) from [<c003c764>]
> >>(irq_exit+0x58/0xb0)
> >>[   68.090000] [<c003c764>] (irq_exit+0x58/0xb0) from [<c0021084>]
> >>(asm_do_IRQ+0x84/0xa4)
> >>[   68.100000] [<c0021084>] (asm_do_IRQ+0x84/0xa4) from [<c002622c>]
> >>(__irq_svc+0x4c/0x98)
> >>[   68.110000] Exception stack(0xc341fdc8 to 0xc341fe10)
> >>[   68.110000] fdc0:                   c07e82c0 00000000 00000200
> >>c4818000 c341fe10 c07e82c0
> >>[   68.120000] fde0: 00000000 c07e82c0 c38d3318 c341e000 bebcee00
> >>010a0b60 c07e83fc c341fe10
> >>[   68.130000] fe00: c0151d54 c023d9c0 60000013 ffffffff
> >>[   68.140000] [<c002622c>] (__irq_svc+0x4c/0x98) from [<c023d9c0>]
> >>(_raw_spin_unlock+0x0/0x48)
> >>[   68.140000] [<c023d9c0>] (_raw_spin_unlock+0x0/0x48) from
> >>[<00000000>] (  (null))
> >>
> >>The soft lockup occurs later
> >>
> >>[  126.750000] BUG: soft lockup - CPU#0 stuck for 61s! [dnp_master:244]
> >>[  126.750000] irq event stamp: 0
> >>[  126.750000] hardirqs last  enabled at (0): [<   (null)>]   (null)
> >>[  126.750000] hardirqs last disabled at (0): [<c0035e30>]
> >>copy_process+0x308/0xe78
> >>[  126.750000] softirqs last  enabled at (0): [<c0035e30>]
> >>copy_process+0x308/0xe78
> >>[  126.750000] softirqs last disabled at (0): [<   (null)>]   (null)
> >>
> >>
> >>The following patch (already tested by Dave, who also reported the bug)
> >>fixes the problem.
> >>
> >>Regards,
> >>
> >>     Claudio
> >>
> >>
> >>
> >>
> >>Subject: atmel_serial: fix spinlock lockup in RS485 code
> >>
> >>Patch to fix a spinlock lockup in the driver that sometimes happens when
> >>the
> >>tasklet starts.
> >>
> >>Signed-off-by: Claudio Scordino<claudio@...dence.eu.com>
> >>Signed-off-by: Dave Bender<codehero@...il.com>
> >>Tested-by: Dave Bender<codehero@...il.com>
> >
> >Acked-by: Nicolas Ferre<nicolas.ferre@...el.com>
> >
> >Claudio, can you please send the patch to Alan with my "Acked-by" and an
> >addition to Linux stable just after the signature lines:
> >
> >Cc: stable<stable@...nel.org>

That address has been invalid since August, please use
stable@...r.kernel.org now.

> Dear Alan,
> 
> 	here is the patch with all the acked-bys.

I'll take care of this.

thanks,

greg k-h
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