> -----Original Message----- > From: Rakesh Pillai <[email protected]> > Sent: Friday, July 24, 2020 11:51 AM > To: 'Johannes Berg' <[email protected]>; > '[email protected]' <[email protected]> > Cc: '[email protected]' <[email protected]>; > '[email protected]' <[email protected]>; > '[email protected]' <[email protected]>; '[email protected]' > <[email protected]>; '[email protected]' <[email protected]>; > '[email protected]' <[email protected]>; > '[email protected]' <[email protected]>; > '[email protected]' <[email protected]> > Subject: RE: [RFC 1/7] mac80211: Add check for napi handle before > WARN_ON > > > > > -----Original Message----- > > From: Johannes Berg <[email protected]> > > Sent: Friday, July 24, 2020 1:37 AM > > To: Rakesh Pillai <[email protected]>; [email protected] > > Cc: [email protected]; [email protected]; > > [email protected]; [email protected]; [email protected]; > > [email protected]; [email protected]; > [email protected] > > Subject: Re: [RFC 1/7] mac80211: Add check for napi handle before > > WARN_ON > > > > On Thu, 2020-07-23 at 23:56 +0530, Rakesh Pillai wrote: > > > > > > > - WARN_ON_ONCE(softirq_count() == 0); > > > > > + WARN_ON_ONCE(napi && softirq_count() == 0); > > > > > > > > FWIW, I'm pretty sure this is incorrect - we make assumptions on > > > > softirqs being disabled in mac80211 for serialization and in place of > > > > some locking, I believe. > > > > > > > > > > I checked this, but let me double confirm. > > > But after this change, no packet is submitted from driver in a softirq > > context. > > > So ideally this should take care of serialization. > > > > I'd guess that we have some reliance on BHs already being disabled, for > > things like u64 sync updates, or whatnot. I mean, we did "rx_ni()" for a > > reason ... Maybe lockdep can help catch some of the issues. > > > > But couldn't you be in a thread and have BHs disabled too? > > This would ideally beat the purpose and possibly hurt the other subsystems > running on the same core. > Hi Johannes, We do have the usage of napi_gro_receive and netif_receive_skb in mac80211. /* deliver to local stack */ if (rx->napi) napi_gro_receive(rx->napi, skb); else netif_receive_skb(skb); Also all the rx_handlers are called under the " rx->local->rx_path_lock" lock. Is the BH disable still required ? > > > > johannes
