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	Fri, 6 May 2016 14:01:23 -0400
Subject: Re: [PATCH v2] rtlwifi: pci: use dev_kfree_skb_irq instead of
 kfree_skb in rtl_pci_reset_trx_ring
To: Alexander Duyck <alexander.duyck@gmail.com>,
	Wang YanQing <udknight@gmail.com>, chaoming_li@realsil.com.cn,
	kvalo@codeaurora.org, linux-wireless@vger.kernel.org,
	Netdev <netdev@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
References: <20160506163351.GA4589@udknight>
 <CAKgT0Uff5dc3_iEjK6GScqgP5_1kcg3YQAv7AH3bzuVDguXiPw@mail.gmail.com>
From: Larry Finger <Larry.Finger@lwfinger.net>
Message-ID: <572CDBF0.9000607@lwfinger.net> (sfid-20160506_200146_437211_D653178C)
Date: Fri, 6 May 2016 13:01:20 -0500
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In-Reply-To: <CAKgT0Uff5dc3_iEjK6GScqgP5_1kcg3YQAv7AH3bzuVDguXiPw@mail.gmail.com>
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On 05/06/2016 12:13 PM, Alexander Duyck wrote:
> On Fri, May 6, 2016 at 9:33 AM, Wang YanQing <udknight@gmail.com> wrote:
>> We can't use kfree_skb in irq disable context, because spin_lock_irqsave
>> make sure we are always in irq disable context, use dev_kfree_skb_irq
>> instead of kfree_skb is better than dev_kfree_skb_any.
>>
>> This patch fix below kernel warning:
>> [ 7612.095528] ------------[ cut here ]------------
>> [ 7612.095546] WARNING: CPU: 3 PID: 4460 at kernel/softirq.c:150 __local_bh_enable_ip+0x58/0x80()
>> [ 7612.095550] Modules linked in: rtl8723be x86_pkg_temp_thermal btcoexist rtl_pci rtlwifi rtl8723_common
>> [ 7612.095567] CPU: 3 PID: 4460 Comm: ifconfig Tainted: G        W       4.4.0+ #4
>> [ 7612.095570] Hardware name: LENOVO 20DFA04FCD/20DFA04FCD, BIOS J5ET48WW (1.19 ) 08/27/2015
>> [ 7612.095574]  00000000 00000000 da37fc70 c12ce7c5 00000000 da37fca0 c104cc59 c19d4454
>> [ 7612.095584]  00000003 0000116c c19d4784 00000096 c10508a8 c10508a8 00000200 c1b42400
>> [ 7612.095594]  f29be780 da37fcb0 c104ccad 00000009 00000000 da37fcbc c10508a8 f21f08b8
>> [ 7612.095604] Call Trace:
>> [ 7612.095614]  [<c12ce7c5>] dump_stack+0x41/0x5c
>> [ 7612.095620]  [<c104cc59>] warn_slowpath_common+0x89/0xc0
>> [ 7612.095628]  [<c10508a8>] ? __local_bh_enable_ip+0x58/0x80
>> [ 7612.095634]  [<c10508a8>] ? __local_bh_enable_ip+0x58/0x80
>> [ 7612.095640]  [<c104ccad>] warn_slowpath_null+0x1d/0x20
>> [ 7612.095646]  [<c10508a8>] __local_bh_enable_ip+0x58/0x80
>> [ 7612.095653]  [<c16b7d34>] destroy_conntrack+0x64/0xa0
>> [ 7612.095660]  [<c16b300f>] nf_conntrack_destroy+0xf/0x20
>> [ 7612.095665]  [<c1677565>] skb_release_head_state+0x55/0xa0
>> [ 7612.095670]  [<c16775bb>] skb_release_all+0xb/0x20
>> [ 7612.095674]  [<c167760b>] __kfree_skb+0xb/0x60
>> [ 7612.095679]  [<c16776f0>] kfree_skb+0x30/0x70
>> [ 7612.095686]  [<f81b869d>] ? rtl_pci_reset_trx_ring+0x22d/0x370 [rtl_pci]
>> [ 7612.095692]  [<f81b869d>] rtl_pci_reset_trx_ring+0x22d/0x370 [rtl_pci]
>> [ 7612.095698]  [<f81b87f9>] rtl_pci_start+0x19/0x190 [rtl_pci]
>> [ 7612.095705]  [<f81970e6>] rtl_op_start+0x56/0x90 [rtlwifi]
>> [ 7612.095712]  [<c17e3f16>] drv_start+0x36/0xc0
>> [ 7612.095717]  [<c17f5ab3>] ieee80211_do_open+0x2d3/0x890
>> [ 7612.095725]  [<c16820fe>] ? call_netdevice_notifiers_info+0x2e/0x60
>> [ 7612.095730]  [<c17f60bd>] ieee80211_open+0x4d/0x50
>> [ 7612.095736]  [<c16891b3>] __dev_open+0xa3/0x130
>> [ 7612.095742]  [<c183fa53>] ? _raw_spin_unlock_bh+0x13/0x20
>> [ 7612.095748]  [<c1689499>] __dev_change_flags+0x89/0x140
>> [ 7612.095753]  [<c127c70d>] ? selinux_capable+0xd/0x10
>> [ 7612.095759]  [<c1689589>] dev_change_flags+0x29/0x60
>> [ 7612.095765]  [<c1700b93>] devinet_ioctl+0x553/0x670
>> [ 7612.095772]  [<c12db758>] ? _copy_to_user+0x28/0x40
>> [ 7612.095777]  [<c17018b5>] inet_ioctl+0x85/0xb0
>> [ 7612.095783]  [<c166e647>] sock_ioctl+0x67/0x260
>> [ 7612.095788]  [<c166e5e0>] ? sock_fasync+0x80/0x80
>> [ 7612.095795]  [<c115c99b>] do_vfs_ioctl+0x6b/0x550
>> [ 7612.095800]  [<c127c812>] ? selinux_file_ioctl+0x102/0x1e0
>> [ 7612.095807]  [<c10a8914>] ? timekeeping_suspend+0x294/0x320
>> [ 7612.095813]  [<c10a256a>] ? __hrtimer_run_queues+0x14a/0x210
>> [ 7612.095820]  [<c1276e24>] ? security_file_ioctl+0x34/0x50
>> [ 7612.095827]  [<c115cef0>] SyS_ioctl+0x70/0x80
>> [ 7612.095832]  [<c1001804>] do_fast_syscall_32+0x84/0x120
>> [ 7612.095839]  [<c183ff91>] sysenter_past_esp+0x36/0x55
>> [ 7612.095844] ---[ end trace 97e9c637a20e8348 ]---
>>
>> Signed-off-by: Wang YanQing <udknight@gmail.com>
>> Cc: Stable <stable@vger.kernel.org>
>> ---
>>   Changes:
>>   v1-v2:
>>   1: add a Cc to stable.
>>
>>   drivers/net/wireless/realtek/rtlwifi/pci.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/net/wireless/realtek/rtlwifi/pci.c b/drivers/net/wireless/realtek/rtlwifi/pci.c
>> index 1ac41b8..99a3a03 100644
>> --- a/drivers/net/wireless/realtek/rtlwifi/pci.c
>> +++ b/drivers/net/wireless/realtek/rtlwifi/pci.c
>> @@ -1572,7 +1572,7 @@ int rtl_pci_reset_trx_ring(struct ieee80211_hw *hw)
>>                                                           true,
>>                                                           HW_DESC_TXBUFF_ADDR),
>>                                                   skb->len, PCI_DMA_TODEVICE);
>> -                               kfree_skb(skb);
>> +                               dev_kfree_skb_irq(skb);
>>                                  ring->idx = (ring->idx + 1) % ring->entries;
>>                          }
>>                          ring->idx = 0;
>
> Is this always called in IRQ context?  You might be better off using
> dev_kfree_skb_any instead if this is something that can be called from
> net_device_ops since that way you avoid having to call into the Tx
> softirq cleanup routine to free the buffers later unless you really
> need it.
>
> - Alex
>

Alex,

Six lines below the change is a spin_unlock_irqrestore(), which is always 
called. I believe that the patch is correct.

Larry