Re: [PATCH 1/1] mac80211: ieee80211_rx_napi: remove warning

[Erik Stromdahl]

On 2017-06-07 23:57, Johannes Berg wrote:

On Sun, 2017-06-04 at 15:11 +0200, Erik Stromdahl wrote:

The softirq count is not always incremented during driver
operation. This is the case for usb and sdio network
drivers.


I'm pretty sure the warning is correct, and we do rely on having
local_bh_disable(), otherwise we may end up taking a soft-IRQ and I
believe there are some things that could get messed up in that case.


Ok, I will make sure to increment the softirq counter before calling
ieee80211_rx then.


So - I think the warning is there for a reason, and drivers should just
local_bh_disable() before calling into that. What's wrong with that?

I guess there is nothing wrong with that, it's just that ath10k does not
call local_bh_disable anywhere in the code.
I guess it is relying on lower layers (pcie?) to do that.
When introducing sdio and usb support these calls will have to be added
explicitly in ath10k.



johannes

Re: [PATCH 1/1] mac80211: ieee80211_rx_napi: remove warning

[Johannes Berg]

On Sun, 2017-06-04 at 15:11 +0200, Erik Stromdahl wrote:
> The softirq count is not always incremented during driver
> operation. This is the case for usb and sdio network
> drivers.

I'm pretty sure the warning is correct, and we do rely on having
local_bh_disable(), otherwise we may end up taking a soft-IRQ and I
believe there are some things that could get messed up in that case.

So - I think the warning is there for a reason, and drivers should just
local_bh_disable() before calling into that. What's wrong with that?

johannes

[PATCH 1/1] mac80211: ieee80211_rx_napi: remove warning

[Erik Stromdahl]

The softirq count is not always incremented during driver
operation. This is the case for usb and sdio network
drivers.

The below warning occurs on the first RX frame pushed to
mac80211 (for usb and sdio):

[   27.414995] [ cut here ]
[   27.416444] WARNING: CPU: 0 PID: 16 at net/mac80211/rx.c:4254 
ieee80211_rx_napi+0x598/0xa30
[   27.419161] Modules linked in: i8042 serio ehci_pci ehci_hcd ath10k_usb 
ath10k_core ath
[   27.421660] CPU: 0 PID: 16 Comm: kworker/0:1 Not tainted 
4.12.0-rc2-wt-ath-ARCH-QEMU+ #5
[   27.424323] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 
1.10.2-20170228_101828-anatol 04/01/2014
[   27.425205] Workqueue: events ath10k_usb_io_comp_work [ath10k_usb]
[   27.425760] task: 88003a730d00 task.stack: c921
[   27.426275] RIP: 0010:ieee80211_rx_napi+0x598/0xa30
[   27.426700] RSP: 0018:c9213c68 EFLAGS: 00010346
[   27.427155] RAX: 8000 RBX: 880039d08500 RCX: 
[   27.427764] RDX: 880039d08500 RSI:  RDI: 880039ff0780
[   27.428371] RBP: c9213d38 R08:  R09: fff0
[   27.429015] R10: eae7e200 R11: 0080 R12: 
[   27.429633] R13: 880039ff1560 R14: 0080 R15: 880039ff0780
[   27.430240] FS:  () GS:88003be0() 
knlGS:
[   27.430914] CS:  0010 DS:  ES:  CR0: 80050033
[   27.431392] CR2: 007fe518 CR3: 3f8c CR4: 06f0
[   27.431982] Call Trace:
[   27.432195]  ? ieee80211_rx_napi+0x18/0xa30
[   27.432553]  ath10k_wmi_event_mgmt_rx+0x233/0x430 [ath10k_core]
[   27.433046]  ath10k_wmi_tlv_op_rx+0x2fb/0x7b0 [ath10k_core]
[   27.433567]  ath10k_wmi_process_rx+0x1a/0x40 [ath10k_core]
[   27.434039]  ath10k_usb_io_comp_work+0x13e/0x1a0 [ath10k_usb]
[   27.434527]  ? __schedule+0x2e3/0x840
[   27.434858]  process_one_work+0x1e0/0x420
[   27.435203]  worker_thread+0x48/0x3f0
[   27.435514]  kthread+0x109/0x140
[   27.435846]  ? process_one_work+0x420/0x420
[   27.436231]  ? kthread_create_on_node+0x70/0x70
[   27.436644]  ret_from_fork+0x2c/0x40
[   27.437046] Code: 70 4c 8b ab d8 00 00 00 44 8b 83 80 00 00 00 41 0f b7 55 
00 4d 89 ee 41 89 d4 41 83 e4 0c e9 88 fc ff ff 4d 89 ec e9 c1 fd ff ff <0f> ff 
0f b6 43 4b 3c 02 0f 86 b2 fa ff ff 0f ff e9 30 fb ff ff
[   27.439114] ---[ end trace 89f286e9814e824a ]---

Signed-off-by: Erik Stromdahl 
---
 net/mac80211/rx.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index 1f75280ba26c..2ec54232817d 100644
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -4251,8 +4251,6 @@ void ieee80211_rx_napi(struct ieee80211_hw *hw, struct 
ieee80211_sta *pubsta,
struct ieee80211_supported_band *sband;
struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
 
-   WARN_ON_ONCE(softirq_count() == 0);
-
if (WARN_ON(status->band >= NUM_NL80211_BANDS))
goto drop;
 
-- 
2.13.0