Date: Tue, 23 Sep 2008 20:25:05 +0200 From: "Paul B. Mahol" <onemda@gmail.com> To: "Mikhail Teterin" <mi+mill@aldan.algebra.com> Cc: stable@freebsd.org Subject: Re: 7.0-stable: a hung process - scheduler bug? Message-ID: <3a142e750809231125o579445baufb5f2676e4d9a2ca@mail.gmail.com> In-Reply-To: <48D92589.8000200@aldan.algebra.com> References: <48D92589.8000200@aldan.algebra.com>
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On 9/23/08, Mikhail Teterin <mi+mill@aldan.algebra.com> wrote: > Hello! > > I was trying to build OpenOffice using all of my 4 CPUs. To be able to > do other work on the machine comfortably, I ran the build under nice, > and assigned real-time priority to the two Xorg processes. > The build started at about 23:10 last night, and hung at 23:46. The > procstat output for the make's process group is: > > PID PPID PGID SID TSID THR LOGIN WCHAN EMUL > COMM > 8371 2425 8371 2425 2425 1 mi wait FreeBSD ELF64 make > 12254 8371 8371 2425 2425 1 mi wait FreeBSD ELF64 sh > 12255 12254 8371 2425 2425 1 mi pause FreeBSD ELF64 > tcsh > 12262 12255 8371 2425 2425 1 mi wait FreeBSD ELF64 > perl5.8.8 > 33010 12262 8371 2425 2425 1 mi wait FreeBSD ELF64 > perl5.8.8 > 33011 33010 8371 2425 2425 1 mi wait FreeBSD ELF64 sh > 33012 33011 8371 2425 2425 1 mi wait FreeBSD ELF64 dmake > 37126 33012 8371 2425 2425 1 mi - FreeBSD ELF64 dmake > > The last line worries me greatly... According to "procstat -t", there is > only one thread there: > > PID TID COMM TDNAME CPU PRI STATE > WCHAN > 37126 100724 dmake - 1 193 sleep - > > And trying to "ktrace -p 37126" returns (even to root, even in /tmp): > > ktrace: ktrace.out: Operation not permitted > > There are no problems ktrace-ing 33012, but nothing comes from there, as > that process simply waits for its child. I guess, the child -- 37126 was > (v)forked to launch a compiler or some such and remains stuck in between > (v)fork and exec somewhere... > > The OS is: FreeBSD 7.0-STABLE/amd64 from Sat Jul 26, 2008 and the box is > otherwise perfectly functional. The scheduling-related options are set > as such: > > options SCHED_4BSD # 4BSD scheduler > options _KPOSIX_PRIORITY_SCHEDULING # POSIX P1003_1B > real-time extensions > > Let me know, what else I can do to help fix this bug -- I'm going to > reboot the machine tonight... Should I switch to SCHED_ULE as a > work-around? SCHED_BSD4 is suboptimal for 4 CPUs, and it is replaced with SCHED_ULE on 7 STABLE.
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