linux-kernel - Re: [PATCH v2 1/3] dmaengine: at

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Date:	Mon, 8 Jun 2015 16:30:52 +0530
From:	Vinod Koul <vinod.koul@...el.com>
To:	Ludovic Desroches <ludovic.desroches@...el.com>
Cc:	linux-arm-kernel@...ts.infradead.org, dmaengine@...r.kernel.org,
	linux-kernel@...r.kernel.org, nicolas.ferre@...el.com,
	maxime.ripard@...e-electrons.com
Subject: Re: [PATCH v2 1/3] dmaengine: at_xdmac: lock fixes

On Mon, Jun 08, 2015 at 10:33:14AM +0200, Ludovic Desroches wrote:
> Using _bh variant for spin locks causes this kind of warning:
> Starting logging: ------------[ cut here ]------------
> WARNING: CPU: 0 PID: 3 at /ssd_drive/linux/kernel/softirq.c:151
> __local_bh_enable_ip+0xe8/0xf4()
> Modules linked in:
> CPU: 0 PID: 3 Comm: ksoftirqd/0 Not tainted 4.1.0-rc2+ #94
> Hardware name: Atmel SAMA5
> [<c0013c04>] (unwind_backtrace) from [<c00118a4>] (show_stack+0x10/0x14)
> [<c00118a4>] (show_stack) from [<c001bbcc>]
> (warn_slowpath_common+0x80/0xac)
> [<c001bbcc>] (warn_slowpath_common) from [<c001bc14>]
> (warn_slowpath_null+0x1c/0x24)
> [<c001bc14>] (warn_slowpath_null) from [<c001e28c>]
> (__local_bh_enable_ip+0xe8/0xf4)
> [<c001e28c>] (__local_bh_enable_ip) from [<c01fdbd0>]
> (at_xdmac_device_terminate_all+0xf4/0x100)
> [<c01fdbd0>] (at_xdmac_device_terminate_all) from [<c02221a4>]
> (atmel_complete_tx_dma+0x34/0xf4)
> [<c02221a4>] (atmel_complete_tx_dma) from [<c01fe4ac>]
> (at_xdmac_tasklet+0x14c/0x1ac)
> [<c01fe4ac>] (at_xdmac_tasklet) from [<c001de58>]
> (tasklet_action+0x68/0xb4)
> [<c001de58>] (tasklet_action) from [<c001dfdc>]
> (__do_softirq+0xfc/0x238)
> [<c001dfdc>] (__do_softirq) from [<c001e140>] (run_ksoftirqd+0x28/0x34)
> [<c001e140>] (run_ksoftirqd) from [<c0033a3c>]
> (smpboot_thread_fn+0x138/0x18c)
> [<c0033a3c>] (smpboot_thread_fn) from [<c0030e7c>] (kthread+0xdc/0xf0)
> [<c0030e7c>] (kthread) from [<c000f480>] (ret_from_fork+0x14/0x34)
> ---[ end trace b57b14a99c1d8812 ]---
> 
> It comes from the fact that devices can called some code from the DMA
> controller with irq disabled. _bh variant is not intended to be used in
> this case since it can enable irqs. Switch to irqsave/irqrestore variant to
> avoid this situation.

Applied, thanks

-- 
~Vinod

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