Date: Mon, 13 Jun 2022 21:47:09 +0000 From: bugzilla-noreply@freebsd.org To: net@FreeBSD.org Subject: [Bug 166724] if_re(4): watchdog timeout Message-ID: <bug-166724-7501-eL2Um9m8Qa@https.bugs.freebsd.org/bugzilla/> In-Reply-To: <bug-166724-7501@https.bugs.freebsd.org/bugzilla/> References: <bug-166724-7501@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D166724 Richard Russo <freebsd@ruka.org> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |freebsd@ruka.org --- Comment #101 from Richard Russo <freebsd@ruka.org> --- I spent some time trying to debug this, without significant results, but I wanted to share what I learned, mostly things that didn't work. My hardware is class=3D0x020000 rev=3D0x0c hdr=3D0x00 vendor=3D0x10ec devic= e=3D0x8168 subvendor=3D0x1462 subdevice=3D0x7850; and I was able to fairly reliably tr= igger the condition with iperf3 -s on the re0 (in a vnet jail), and iperf3 -c --b= idir on another interface. My hardware is fairly meager, Intel G3470, using a multiport Intel em card for the otherside of the iperf3 testing. Using the kernel driver (13.1-RELEASE), I would tend to see traffic stall a= nd timeouts be reported within one minute, although sometimes within a few seconds. Using the vendor driver from net/realtek-re-kmod, I was unable to reproduce the error condition. There's a fair amount of differences between the two drivers, and I tried a bunch of things, but could never pass my test. Sending more transmit reques= ts didn't help; the vendor driver sends it twice, but that doesn't seem to hel= p; sending TX requests in the watchdog handler didn't help either. I noticed that the Tx queue would usually be stuck on the 2nd segment of a = two or three segment packet, so I tried adding m_defrag to make all the packets= a single segment. That didn't work either. There didn't seem to be a pattern = of which Tx segment the NIC would get stuck on, or anything obvious about the = data addresses. I also tried messing with the reset to maybe make that more reliable. The vendor driver does reset a little bit differently, but nothing there made things reliable for me either. After a few resets, the NIC just doesn't see= m to start sending again; until a reboot (at least with my NIC; I've seen some reports that a power cycle is required). Reading the tx/rx registers before setting them, I saw that those are retained across reboots, so the device doesn't seem to be getting fully reset, which might explain some reporter's need to power cycle. I suspect there's something in the mostly opaque vendor initialization code, that puts the device in a better mode where it doesn't get stuck (at least = with my test loads). I do notice that the vendor initialization causes the devic= e to emit ethernet pause frames, which doesn't happen with the kernel code. One thing I was able to make a positive difference with though, the kernel reset doesn't clear the RX/TX buffers, although it frees the associated mbu= fs. Sometimes during a reset or shortly afterwards, the NIC is still using those descriptor arrays; so I would see weird packets apparently coming in on re0= via tcpdump, many of them looking like recently used mbufs on other interfaces.= I also saw some bizarre packets RXed by the em NIC connected to re0, and some evidence of other NICs receiving corrupted mbufs. Using explicit_bzero during descriptor setup seemed to help, as well as tur= ning off the CMD_OWN flag on the descriptors during re_stop. It's obviously a bit tricky if the device is acknowledging a command reset, but not actually ful= ly resetting. I don't have an IOMMU system, but I'd guess if you had that, you could get more information about what's going on. Running with INVARIANTS showed some use after free errors, which I believe = are related to the device using the mbufs, although it was hard to trigger and difficult to debug. --=20 You are receiving this mail because: You are the assignee for the bug. You are on the CC list for the bug.=
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