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Subject: Re: [PATCH v2 4/4] ARM: OMAP2+: omap_device: fix crash on omap_device
 removal
To: Grygorii Strashko <grygorii.strashko@ti.com>,
        "David S. Miller" <davem@davemloft.net>, <netdev@vger.kernel.org>,
        Mugunthan V N <mugunthanvnm@ti.com>
References: <20160728175037.22053-1-grygorii.strashko@ti.com>
 <20160728175037.22053-5-grygorii.strashko@ti.com>
CC: Sekhar Nori <nsekhar@ti.com>, <linux-kernel@vger.kernel.org>,
        <linux-omap@vger.kernel.org>, Tony Lindgren <tony@atomide.com>,
        Tero Kristo <t-kristo@ti.com>
From: Peter Ujfalusi <peter.ujfalusi@ti.com>
Message-ID: <ca582e58-8c97-67cb-8f1c-778e4c7b448e@ti.com>
Date: Fri, 29 Jul 2016 08:15:16 +0300
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On 07/28/16 20:50, Grygorii Strashko wrote:
> Below call chain causes system crash when OMAP device is
> removed by calling of_platform_depopulate()/device_del():

Should you swap 3 <-> 4 in the series?
Currently patch 3 will introduce the crash you are fixing in patch 4...

> 
> device_del()
> - blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
>  			     BUS_NOTIFY_DEL_DEVICE, dev);
>   - _omap_device_notifier_call()
>     - omap_device_delete()
>       - od->pdev->archdata.od = NULL;
> 	kfree(od->hwmods);
> 	kfree(od);
>   - bus_remove_device()
>     - device_release_driver()
>       - __device_release_driver()
> 	- pm_runtime_get_sync()
> 	   - _od_runtime_resume()
> 	     - omap_hwmod_enable() <- OOPS od's delted already
> 
> Backtrace:
> Unable to handle kernel NULL pointer dereference at virtual address 0000000d
> pgd = eb100000
> [0000000d] *pgd=ad6e1831, *pte=00000000, *ppte=00000000
> Internal error: Oops: 17 [#1] PREEMPT SMP ARM
> CPU: 1 PID: 1273 Comm: modprobe Not tainted 4.4.15-rt19-00115-ge4d3cd3-dirty #68
> Hardware name: Generic DRA74X (Flattened Device Tree)
> task: eb1ee800 ti: ec962000 task.ti: ec962000
> PC is at omap_device_enable+0x10/0x90
> LR is at _od_runtime_resume+0x10/0x24
> [...]
> [<c00299dc>] (omap_device_enable) from [<c0029a6c>] (_od_runtime_resume+0x10/0x24)
> [<c0029a6c>] (_od_runtime_resume) from [<c04ad404>] (__rpm_callback+0x20/0x34)
> [<c04ad404>] (__rpm_callback) from [<c04ad438>] (rpm_callback+0x20/0x80)
> [<c04ad438>] (rpm_callback) from [<c04aee28>] (rpm_resume+0x48c/0x964)
> [<c04aee28>] (rpm_resume) from [<c04af360>] (__pm_runtime_resume+0x60/0x88)
> [<c04af360>] (__pm_runtime_resume) from [<c04a4974>] (__device_release_driver+0x30/0x100)
> [<c04a4974>] (__device_release_driver) from [<c04a4a60>] (device_release_driver+0x1c/0x28)
> [<c04a4a60>] (device_release_driver) from [<c04a38c0>] (bus_remove_device+0xec/0x144)
> [<c04a38c0>] (bus_remove_device) from [<c04a0764>] (device_del+0x10c/0x210)
> [<c04a0764>] (device_del) from [<c04a67b0>] (platform_device_del+0x18/0x84)
> [<c04a67b0>] (platform_device_del) from [<c04a6828>] (platform_device_unregister+0xc/0x20)
> [<c04a6828>] (platform_device_unregister) from [<c05adcfc>] (of_platform_device_destroy+0x8c/0x90)
> [<c05adcfc>] (of_platform_device_destroy) from [<c04a02f0>] (device_for_each_child+0x4c/0x78)
> [<c04a02f0>] (device_for_each_child) from [<c05adc5c>] (of_platform_depopulate+0x30/0x44)
> [<c05adc5c>] (of_platform_depopulate) from [<bf123920>] (cpsw_remove+0x68/0xf4 [ti_cpsw])
> [<bf123920>] (cpsw_remove [ti_cpsw]) from [<c04a68d8>] (platform_drv_remove+0x24/0x3c)
> [<c04a68d8>] (platform_drv_remove) from [<c04a49c8>] (__device_release_driver+0x84/0x100)
> [<c04a49c8>] (__device_release_driver) from [<c04a4b20>] (driver_detach+0xac/0xb0)
> [<c04a4b20>] (driver_detach) from [<c04a3be8>] (bus_remove_driver+0x60/0xd4)
> [<c04a3be8>] (bus_remove_driver) from [<c00d9870>] (SyS_delete_module+0x184/0x20c)
> [<c00d9870>] (SyS_delete_module) from [<c0010540>] (ret_fast_syscall+0x0/0x1c)
> Code: e3500000 e92d4070 1590630c 01a06000 (e5d6300d)
> 
> Hence, fix it by using BUS_NOTIFY_REMOVED_DEVICE event for OMAP device
> deletion which is sent when DD has finished processing of device
> deletion.
> 
> Cc: Tony Lindgren <tony@atomide.com>
> Cc: Tero Kristo <t-kristo@ti.com>
> Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
> ---
>  arch/arm/mach-omap2/omap_device.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm/mach-omap2/omap_device.c b/arch/arm/mach-omap2/omap_device.c
> index f7ff3b9..208f115 100644
> --- a/arch/arm/mach-omap2/omap_device.c
> +++ b/arch/arm/mach-omap2/omap_device.c
> @@ -194,7 +194,7 @@ static int _omap_device_notifier_call(struct notifier_block *nb,
>  	int err;
>  
>  	switch (event) {
> -	case BUS_NOTIFY_DEL_DEVICE:
> +	case BUS_NOTIFY_REMOVED_DEVICE:
>  		if (pdev->archdata.od)
>  			omap_device_delete(pdev->archdata.od);
>  		break;
> 


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