linux-kernel - Re: [PATCH 2/3] led-triggers: use atomic kzalloc during led trigger registering

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Message-ID: <20120308092913.GF14173@pengutronix.de>
Date:	Thu, 8 Mar 2012 10:29:13 +0100
From:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
To:	Bryan Wu <bryan.wu@...onical.com>
Cc:	rpurdie@...ys.net, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org, linus.walleij@...aro.org,
	linux@....linux.org.uk
Subject: Re: [PATCH 2/3] led-triggers: use atomic kzalloc during led trigger
 registering

On Thu, Mar 08, 2012 at 05:11:02PM +0800, Bryan Wu wrote:
> kzalloc might cause sleep and will generate some warning detected by lockdep,
> when call led_trigger_register_simple on each cpu cores in SMP. This patch fix
> this.
The obvious (and IMHO better) alternative is to call
led_trigger_register_simple from non-atomic context.

For registering this should be OK, shouldn't it?

Best regards
Uwe

> 
> [    1.999938] ------------[ cut here ]------------
> [    2.004791] WARNING: at kernel/lockdep.c:2664 lockdep_trace_alloc+0xd8/0xf0()
> [    2.012298] Modules linked in:
> [    2.015563] [<c001b0cc>] (unwind_backtrace+0x0/0xf0) from [<c0052408>] (warn_slowpath_common+0x4c/0x64)
> [    2.025451] [<c0052408>] (warn_slowpath_common+0x4c/0x64) from [<c005243c>] (warn_slowpath_null+0x1c/0x24)
> [    2.035583] [<c005243c>] (warn_slowpath_null+0x1c/0x24) from [<c008be28>] (lockdep_trace_alloc+0xd8/0xf0)
> [    2.045684] [<c008be28>] (lockdep_trace_alloc+0xd8/0xf0) from [<c00feeb4>] (kmem_cache_alloc_trace+0x2c/0x148)
> [    2.056213] [<c00feeb4>] (kmem_cache_alloc_trace+0x2c/0x148) from [<c03770a0>] (led_trigger_register_simple+0x20/0x74)
> [    2.067474] [<c03770a0>] (led_trigger_register_simple+0x20/0x74) from [<c0627a30>] (ledtrig_cpu_register+0x4c/0x8c)
> [    2.078460] [<c0627a30>] (ledtrig_cpu_register+0x4c/0x8c) from [<c0094ca4>] (generic_smp_call_function_single_interrupt+0xcc/0x138)
> [    2.090911] [<c0094ca4>] (generic_smp_call_function_single_interrupt+0xcc/0x138) from [<c0008408>] (do_IPI+0xb0/0x128)
> [    2.102172] [<c0008408>] (do_IPI+0xb0/0x128) from [<c045921c>] (__irq_svc+0x3c/0x100)
> [    2.110412] Exception stack(0xc07adf70 to 0xc07adfb8)
> [    2.115722] df60:                                     c07c80f8 0000fb45 00000000 c07c80f8
> [    2.124328] df80: c07ac000 c0837be4 c0464b64 c07c9d8c 00000000 411fc092 00000000 00000000
> [    2.132934] dfa0: c0649760 c07adfb8 c07c5c58 c0014d50 20000013 ffffffff
> [    2.139892] [<c045921c>] (__irq_svc+0x3c/0x100) from [<c0014d50>] (default_idle+0x30/0x38)
> [    2.148590] [<c0014d50>] (default_idle+0x30/0x38) from [<c0014f74>] (cpu_idle+0xb4/0xf4)
> [    2.157135] [<c0014f74>] (cpu_idle+0xb4/0xf4) from [<c0602778>] (start_kernel+0x2a8/0x2fc)
> [    2.165832] [<c0602778>] (start_kernel+0x2a8/0x2fc) from [<80008040>] (0x80008040)
> [    2.173797] ---[ end trace 97549d21d8dad3f5 ]---
> 
> Signed-off-by: Bryan Wu <bryan.wu@...onical.com>
> ---
>  drivers/leds/led-triggers.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/leds/led-triggers.c b/drivers/leds/led-triggers.c
> index 46b4c76..74d0ba7 100644
> --- a/drivers/leds/led-triggers.c
> +++ b/drivers/leds/led-triggers.c
> @@ -255,7 +255,7 @@ void led_trigger_register_simple(const char *name, struct led_trigger **tp)
>  	struct led_trigger *trigger;
>  	int err;
>  
> -	trigger = kzalloc(sizeof(struct led_trigger), GFP_KERNEL);
> +	trigger = kzalloc(sizeof(struct led_trigger), GFP_ATOMIC);
>  
>  	if (trigger) {
>  		trigger->name = name;
> -- 
> 1.7.9
> 
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> 

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
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