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Date: Sun, 11 Aug 2019 21:36:03 -0700 (PDT) From: David Miller <davem@...emloft.net> To: idosch@...sch.org Cc: netdev@...r.kernel.org, jiri@...lanox.com, petrm@...lanox.com, richardcochran@...il.com, mlxsw@...lanox.com, idosch@...lanox.com Subject: Re: [PATCH net] mlxsw: spectrum_ptp: Keep unmatched entries in a linked list From: Ido Schimmel <idosch@...sch.org> Date: Sun, 11 Aug 2019 10:48:37 +0300 > From: Petr Machata <petrm@...lanox.com> > > To identify timestamps for matching with their packets, Spectrum-1 uses a > five-tuple of (port, direction, domain number, message type, sequence ID). > If there are several clients from the same domain behind a single port > sending Delay_Req's, the only thing differentiating these packets, as far > as Spectrum-1 is concerned, is the sequence ID. Should sequence IDs between > individual clients be similar, conflicts may arise. That is not a problem > to hardware, which will simply deliver timestamps on a first comes, first > served basis. > > However the driver uses a simple hash table to store the unmatched pieces. > When a new conflicting piece arrives, it pushes out the previously stored > one, which if it is a packet, is delivered without timestamp. Later on as > the corresponding timestamps arrive, the first one is mismatched to the > second packet, and the second one is never matched and eventually is GCd. > > To correct this issue, instead of using a simple rhashtable, use rhltable > to keep the unmatched entries. > > Previously, a found unmatched entry would always be removed from the hash > table. That is not the case anymore--an incompatible entry is left in the > hash table. Therefore removal from the hash table cannot be used to confirm > the validity of the looked-up pointer, instead the lookup would simply need > to be redone. Therefore move it inside the critical section. This > simplifies a lot of the code. > > Fixes: 8748642751ed ("mlxsw: spectrum: PTP: Support SIOCGHWTSTAMP, SIOCSHWTSTAMP ioctls") > Reported-by: Alex Veber <alexve@...lanox.com> > Signed-off-by: Petr Machata <petrm@...lanox.com> > Signed-off-by: Ido Schimmel <idosch@...lanox.com> Applied.
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