On 09.04.2021 22:27, Vladimir Oltean wrote:
From: Vladimir Oltean <vladimir.olt...@nxp.com>The blamed commit introduced a bit in the TX software buffer descriptor structure for determining whether a BD is final or not; we rearm the TX interrupt vector for every frame (hence final BD) transmitted. But there is a problem with the patch: it replaced a condition whose expression is a bool which was evaluated at the beginning of the "while" loop with a bool expression that is evaluated on the spot: tx_swbd->is_eof. The problem with the latter expression is that the tx_swbd has already been incremented at that stage, so the tx_swbd->is_eof check is in fact with the _next_ software BD. Which is _not_ final. The effect is that the CPU is in 100% load with ksoftirqd because it does not acknowledge the TX interrupt, so the handler keeps getting called again and again. The fix is to restore the code structure, and keep the local bool is_eof variable, just to assign it the tx_swbd->is_eof value instead of !!tx_swbd->skb. Fixes: d504498d2eb3 ("net: enetc: add a dedicated is_eof bit in the TX software BD") Reported-by: Alex Marginean <alexandru.margin...@nxp.com> Signed-off-by: Vladimir Oltean <vladimir.olt...@nxp.com>
Reviewed-by: Claudiu Manoil <claudiu.man...@nxp.com>
