> -----Original Message----- > From: Vladimir Oltean <olte...@gmail.com> > Sent: Monday, December 16, 2019 3:10 PM > To: richardcoch...@gmail.com > Cc: linuxptp-devel@lists.sourceforge.net > Subject: [Linuxptp-devel] [PATCH 0/3] More strict checking against kernel bugs > > The reordering issue reported by me initially on the linuxptp-devel > list [0] with the sja1105 DSA driver turned out not to be a reordering > issue at all, in fact. > > Due to a kernel bug described in this patch [1], the DSA driver was in > race with the master Ethernet driver and would occasionally (very > rarely) deliver 2 TX timestamps to ptp4l on the event socket. > > The first TX timestamp is consumed in-band in the raw_send function. > The second is caught by the main poll() syscall in the main ptp4l event > loop - clock_poll(). > > When poll() sees the second TX-timestamped skb, it returns with revents > == (POLLIN | POLLERR). But the main loop only checks for POLLIN, and > says "yay, there's data!". So it proceeds to call recvmsg() with flags=0 > (instead of MSG_ERRQUEUE), so it doesn't see any data in > sk->sk_receive_queue. So, surprise, false alarm, the data that woke it > up was in sk->sk_error_queue. The ptp4l process goes to sleep waiting > for data. > > It sleeps for a whole sync interval. > > When it wakes up, it wakes up with the next sync, even though the > previous sync's follow-up may have arrived in the meantime. > > Apparent reordering. > > Ptp4l does not print anything, it just appears to freeze. > > So this patch set aims to improves the error reporting in ptp4l, such > that tracing back to the root cause is easier next time, and the problem > does not blow up into other, completely unrelated things. >
Nice analysis. Thanks, Jake > [0]: https://sourceforge.net/p/linuxptp/mailman/message/36773629/ > [1]: https://patchwork.ozlabs.org/patch/1210871/ > > Vladimir Oltean (3): > ptp4l: Call recvmsg() with the MSG_DONTWAIT flag > clock: Dump unexpected packets received on the error queues of sockets > port: Signal sync/follow-up mismatch events loudly > > clock.c | 11 +++++++++++ > msg.c | 12 ++++++++++++ > msg.h | 7 +++++++ > port.c | 21 +++++++++++++++++++++ > raw.c | 2 +- > udp.c | 2 +- > udp6.c | 2 +- > 7 files changed, 54 insertions(+), 3 deletions(-) > > -- > 2.17.1 > > > > _______________________________________________ > Linuxptp-devel mailing list > Linuxptp-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/linuxptp-devel _______________________________________________ Linuxptp-devel mailing list Linuxptp-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linuxptp-devel
