2021-04-21 04:23:43

by Jarvis Jiang

Subject: [PATCH v1] net: Qcom WWAN control driver: fix the rx_budget was eaten incorrectly

mhi_wwan_rx_budget_dec() should check the value of mhiwwan->rx_budget
before the decrement, not the value after decrement.

When mhiwwan->rx_budget = 1, mhi_wwan_rx_budget_dec() will always return
false, which will cause the mhi_wwan_ctrl_refill_work() not to queue rx
buffers to transfer ring any more, and rx will be stuck.

This patch was tested with Ubuntu 20.04 X86_64 PC as host

Signed-off-by: Jarvis Jiang <[email protected]>
---
drivers/net/wwan/mhi_wwan_ctrl.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/net/wwan/mhi_wwan_ctrl.c b/drivers/net/wwan/mhi_wwan_ctrl.c
index 11475ade4be5..721edf5a238f 100644
--- a/drivers/net/wwan/mhi_wwan_ctrl.c
+++ b/drivers/net/wwan/mhi_wwan_ctrl.c
@@ -56,12 +56,12 @@ static bool mhi_wwan_rx_budget_dec(struct mhi_wwan_dev *mhiwwan)

spin_lock(&mhiwwan->rx_lock);

- if (mhiwwan->rx_budget)
- mhiwwan->rx_budget--;
-
if (mhiwwan->rx_budget && test_bit(MHI_WWAN_RX_REFILL, &mhiwwan->flags))
ret = true;

+ if (mhiwwan->rx_budget)
+ mhiwwan->rx_budget--;
+
spin_unlock(&mhiwwan->rx_lock);

return ret;
--
2.25.1

2021-04-21 06:39:33

by Loic Poulain

Subject: Re: [PATCH v1] net: Qcom WWAN control driver: fix the rx_budget was eaten incorrectly

Hi Jarvis,

On Wed, 21 Apr 2021 at 05:57, Jarvis Jiang <[email protected]> wrote:
>
> mhi_wwan_rx_budget_dec() should check the value of mhiwwan->rx_budget
> before the decrement, not the value after decrement.
>
> When mhiwwan->rx_budget = 1, mhi_wwan_rx_budget_dec() will always return
> false, which will cause the mhi_wwan_ctrl_refill_work() not to queue rx
> buffers to transfer ring any more, and rx will be stuck.
>
> This patch was tested with Ubuntu 20.04 X86_64 PC as host
>
> Signed-off-by: Jarvis Jiang <[email protected]>

Thanks for the patch, but a similar change for this issue has just
been merged in net-next (a926c025d56b net: wwan: mhi_wwan_ctrl: Fix RX
buffer starvation).

Regards,
Loic