On Thu, Apr 14, 2022 at 10:42:59AM +0200, Jakub Kicinski wrote:
On Thu, 14 Apr 2022 15:29:34 +0800 Tan Tee Min wrote:
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c @@ -279,10 +279,11 @@ static int dwmac4_wrback_get_rx_timestamp_status(void *desc, void *next_desc, /* Check if timestamp is OK from context descriptor */ do { ret = dwmac4_rx_check_timestamp(next_desc);
if (ret < 0)
if (ret <= 0) goto exit; i++;
fsleep(1);This is nutty. Why isn't this code using proper deferral mechanisms like work or kthread?
Appreciate your comment. The dwmac4_wrback_get_rx_timestamp_status() is called by stmmac_rx() function which is scheduled by NAPI framework. Do we still need to create deferred work inside NAPI work? Would you mind to explain it more in detail?
fsleep() is a big hammer, can you try cpu_relax() and bumping the max loop count a little?
Thanks for the suggestion! I tried cpu_relax(), unfortunately the issue still happens when the system is in a high-load situation.
I agree that the fsleep(1) (=1us) is a big hammer. Thus in order to improve this, I’ve figured out a smaller delay time that is enough for the context descriptor to be ready which is ndelay(500) (=500ns).
Would you think this is more acceptable?