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Date:	Fri, 29 Jul 2016 15:52:39 +0300
From:	Grygorii Strashko <grygorii.strashko@...com>
To:	Peter Ujfalusi <peter.ujfalusi@...com>,
	"David S. Miller" <davem@...emloft.net>, <netdev@...r.kernel.org>,
	Mugunthan V N <mugunthanvnm@...com>
CC:	Sekhar Nori <nsekhar@...com>, <linux-kernel@...r.kernel.org>,
	<linux-omap@...r.kernel.org>, Tony Lindgren <tony@...mide.com>,
	Tero Kristo <t-kristo@...com>
Subject: Re: [PATCH v2 4/4] ARM: OMAP2+: omap_device: fix crash on omap_device
 removal

On 07/29/2016 08:15 AM, Peter Ujfalusi wrote:
> 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...

No. The key function here is device_del() - of_device_unregister(), 
which was used previously has the same issue:
   of_device_unregister() -> device_unregister() ->device_del()

In general all these patches are independent and they were created just 
in bugs detection order.

>
>>
>> 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@...mide.com>
>> Cc: Tero Kristo <t-kristo@...com>
>> Signed-off-by: Grygorii Strashko <grygorii.strashko@...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;
>>
>
>


-- 
regards,
-grygorii

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