Re: [PATCH v2] rtlwifi: pci: use dev_kfree_skb_irq instead of kfree_skb in rtl_pci_reset_trx_ring

[Alexander Duyck]

On Fri, May 6, 2016 at 9:33 AM, Wang YanQing <udknight@xxxxxxxxx> 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@xxxxxxxxx>
> Cc: Stable <stable@xxxxxxxxxxxxxxx>
> ---
>  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