[Bug 227285] File descriptor passing does not work reliably on SMP system (cache coherency issue?)
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=227285 Jan Kokemüller changed: What|Removed |Added Attachment #192213|0 |1 is obsolete|| Attachment #192214|0 |1 is obsolete|| Attachment #192216|0 |1 is obsolete|| --- Comment #5 from Jan Kokemüller --- Created attachment 192350 --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=192350&action=edit tar archive with test program, Dtrace script and log output I've attached a program that reproduces the bug faster. I've also updated the Dtrace script and added some new log output. The Dtrace script now prints all socantrcvmore() calls, not only those from "a.out". It turns out that the kernel sometimes closes the socket in the unp garbage collector (look for sockbuf f800adec3b50 in the debug log). So there probably is no cache issue after all. Investigating further... -- You are receiving this mail because: You are the assignee for the bug. ___ freebsd-bugs@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-bugs To unsubscribe, send any mail to "freebsd-bugs-unsubscr...@freebsd.org"
[Bug 227285] File descriptor passing does not work reliably on SMP system (cache coherency issue?)
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=227285 --- Comment #4 from Jan Kokemüller --- To uncover the bug it helps to run multiple instances at the same time and to remove the debug output or to pipe it into /dev/null. After a few seconds, at least some instances should be dead. I've tested only amd64 for now. I could reproduce it on stock FreeBSD 10/11 systems: FreeBSD 10.3-RELEASE-p24 FreeBSD 10.3-RELEASE-p24 #0: Wed Nov 15 04:57:40 UTC 2017 r...@amd64-builder.daemonology.net:/usr/obj/usr/src/sys/GENERIC amd64 hw.model: Intel(R) Celeron(R) CPU N3150 @ 1.60GHz FreeBSD 11.1-RELEASE-p7 FreeBSD 11.1-RELEASE-p7 #0: Tue Mar 6 09:33:30 UTC 2018 r...@amd64-builder.daemonology.net:/usr/obj/usr/src/sys/GENERIC amd64 hw.model: Intel(R) Celeron(R) CPU G530 @ 2.40GHz -- You are receiving this mail because: You are the assignee for the bug. ___ freebsd-bugs@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-bugs To unsubscribe, send any mail to "freebsd-bugs-unsubscr...@freebsd.org"
[Bug 227285] File descriptor passing does not work reliably on SMP system (cache coherency issue?)
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=227285 Jan Kokemüller changed: What|Removed |Added Attachment #192211|0 |1 is obsolete|| Attachment #192216|text/x-csrc |text/plain mime type|| --- Comment #3 from Jan Kokemüller --- Created attachment 192216 --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=192216&action=edit test program (fixed) I've mistakenly uploaded the program with a workaround applied. Here is a fixed version with the workaround behind a ifdef. -- You are receiving this mail because: You are the assignee for the bug. ___ freebsd-bugs@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-bugs To unsubscribe, send any mail to "freebsd-bugs-unsubscr...@freebsd.org"
[Bug 227285] File descriptor passing does not work reliably on SMP system (cache coherency issue?)
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=227285 --- Comment #2 from Jan Kokemüller --- Created attachment 192214 --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=192214&action=edit excerpt of Dtrace script output Here is part of the Dtrace debug log. When 'got err' is printed it means that the parent could not read the byte from the child. At this point the address of the receive sockbuf is 'f801071df148' and the SBS_CANTRCVMORE flag is set (CPU 1). However, further above, this sockbuf looks fine in the child (CPU 3) and there aren't any calls to socantrcvmore_locked() in the meantime. Even further above, this sockbuf was destroyed by the parent in a previous iteration (CPU 1) and therefore SBS_CANTRCVMORE is set. But this should not affect the current iteration. It looks like the memory from the child process on CPU 3 isn't made visible to CPU 1 properly. -- You are receiving this mail because: You are the assignee for the bug. ___ freebsd-bugs@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-bugs To unsubscribe, send any mail to "freebsd-bugs-unsubscr...@freebsd.org"
[Bug 227285] File descriptor passing does not work reliably on SMP system (cache coherency issue?)
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=227285 Jan Kokemüller changed: What|Removed |Added Attachment #192213|text/x-dsrc |text/plain mime type|| --- Comment #1 from Jan Kokemüller --- Created attachment 192213 --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=192213&action=edit Dtrace script for debugging Here is a Dtrace script that could be helpful in tracing down the issue. -- You are receiving this mail because: You are the assignee for the bug. ___ freebsd-bugs@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-bugs To unsubscribe, send any mail to "freebsd-bugs-unsubscr...@freebsd.org"
[Bug 227285] File descriptor passing does not work reliably on SMP system (cache coherency issue?)
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=227285 Bug ID: 227285 Summary: File descriptor passing does not work reliably on SMP system (cache coherency issue?) Product: Base System Version: CURRENT Hardware: Any OS: Any Status: New Severity: Affects Some People Priority: --- Component: kern Assignee: freebsd-bugs@FreeBSD.org Reporter: jan.kokemuel...@gmail.com Attachment #192211 text/plain mime type: Created attachment 192211 --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=192211&action=edit test program The attached program repeatedly spawns a child process that creates a socketpair. One socket is passed back to the parent. One byte is written into the other end. The parent should be able to read this byte, but sometimes 0 (EOF) is returned. It seems that the parent reuses stale socket/sockbuf memory from prior iterations. To simplify the fd passing I've used fd_send/fd_recv from libnv. Those use SCM_RIGHTS under the hood. The program must be compiled with 'cc -O3 fdpass.c -lnv'. -- You are receiving this mail because: You are the assignee for the bug. ___ freebsd-bugs@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-bugs To unsubscribe, send any mail to "freebsd-bugs-unsubscr...@freebsd.org"
