Direct, indi­rect and explic­it depen­den­cies in progams/ports

The dis­cus­sion about direct and indi­rect depen­den­cies is com­ing up again on the FreeB­SD mail­inglists. Seems I should make some blog post about it, maybe it makes this top­ic more find­able than my post­ings in the mail­inglists.

Some def­i­n­i­tions:

  • A direct depen­den­cy from A to B is when program/port A uses sym­bols from library/port B.
  • An indi­rect depen­den­cy from A to C is when program/port A uses sym­bols from library/port B but no sym­bols from library/port C, and library/port B uses sym­bols from library/port C.
  • An explic­it depen­den­cy from A to C is when it is a direct or indi­rect depen­den­cy A to C, and when the compiler-time-link­er added an explic­it ref­er­ence to C to the program/lib of A.

Ide­al­ly we have no indi­rect depen­den­cies in the explic­it depen­den­cies, only direct depen­den­cies. Unfor­tu­nate­ly in real­i­ty we also have indi­rect depen­den­cies there. This has at least two caus­es:

  1. libtool (at least 1.x) does not (or was not) come with a hint on FreeB­SD, which tells that the run-time-linker is recur­sive­ly resolv­ing depen­den­cies.
  2. Some pkg-con­fig setups list indi­rect depen­den­cies as explic­it depen­den­cies (IIRC it depends if Requires.private and/or Libs.private is used in the .pc file or not; if it is used, there should be no indi­rect depen­den­cy appear from this soft­ware, but I am not 100% sure about this).

Three years ago I wrote /usr/ports/Tools/scripts/explicit_lib_depends.sh, it looks at the files of a giv­en port (it needs to be installed), and prints out explic­it depen­den­cies. Because of the indi­rect depen­den­cies which could be list­ed there, this list is not a list of ports which are real depen­den­cies from a source code point of view, but it reflects the link-time real­i­ty. If a port C shows up there, the port which is checked needs to be rebuild in case the ABI of library/port C changes.

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Men­tor­ing again in the GSoC

Seems that I will active­ly men­tor again in this Google Sum­mer of Code (as opposed to just review the sub­mis­sions from stu­dents and/or act­ing as a fall-back men­tor).

The project I will men­tor is the “Make option­al ker­nel sub­sys­tems reg­is­ter them­selves via sysctl”-one from the FreeB­SD ideas page.

The stu­dent already got into con­tact with me and it looks like he is moti­vat­ed (he is already sub­scribed to sev­er­al FreeB­SD mail­inglists, which is not a require­ment we have in our GSoC docs).

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Some fix­es for ZFS on 7‑stable (more testers want­ed)

Due to the prob­lems with a 7-sta­ble machine, I had a look at some unmerged fix­es for ZFS (58 changes not merged).

I back­port­ed some of those changes from 8‑stable to 7‑stable, I have this run­ning on one 7‑stable machine. I would like to get some more feed­back for it (even an “it works for me” would be great). The main part of this change is that the FreeB­SD taskqueue is used now instead of the open­so­laris one (and some oth­er changes which may improve the ZFS expe­ri­ence).

It would also be nice if some­one could have a look at the FIRST_THREAD_IN_PROC part. Can there be more than one thread at this place (I do not think so) and I should use FOREACH_THREAD_IN_PROC_instead?

How to apply:

  • cd /usr/src/
  • fetch http://www.Leidinger.net/FreeB­SD/test/releng7_zfs_merge3.diff
  • fetch http://www.Leidinger.net/FreeBSD/test/opensolaris_taskq.c
  • fetch http://www.Leidinger.net/FreeBSD/test/taskq.h
  • mv taskq.h sys/cddl/contrib/opensolaris/uts/common/sys/taskq.h
  • mv opensolaris_taskq.c sys/cddl/com­pat/opensolaris/kern/opensolaris_taskq.c
  • patch ‑p 0 –qui­et <releng7_zfs_merge3.diff
  • ignore the 2 .rej files
  • rm ‑f sys/cddl/compat/opensolaris/sys/taskq_impl.h*
  • rm ‑f sys/cddl/compat/opensolaris/sys/taskq.h*
  • rm ‑f sys/cddl/contrib/opensolaris/uts/common/os/taskq.c*
  • rebuild ker­nel

I do not list all of those 16 of 58 out­stand­ing patch­es which are cov­ered here, a detailed list can be found on the sta­ble and fs mail­inglists.

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Sta­bil­i­ty prob­lems with 7‑stable

On the machine where I host this blog, I have/had some sta­bil­i­ty prob­lems.

Last week I updat­ed the machine from FreeB­SD 7.1‑pX to 7.2‑p5 (GENERIC ker­nel in both cas­es). 5 – 10 Min­utes after the reboot into the new ver­sion the machine had a dead­lock. After some road­blocks (order­ing a KVM-switch from the hoster, the KVM-switch not work­ing with a proxy (dur­ing lunchtime at work), a bro­ken video-capture of the KVM-switch and a replace­ment on Mon­day morn­ing to not pay the WE-fees), I spend a big part of the night to get it sta­ble. I tried dis­abling SMP, enabling INVARIANTS and WITNESS, chang­ing the sched­uler, cut­ting the soft­ware mir­ror (to rule out a mis­match between the con­tent of the disks after all the hard reboots) and updat­ing to 7‑stable.

Unfor­tu­nate­ly noth­ing helped. 🙁

Googling a lit­tle bit around (it is a AMD Dual-Core sys­tem with NVidia MCP61 chipset) was lead­ing me to a post on the mail­inglists from 2008 which talks about an issue with the buffer cache. I do not know if this is still an issue (I have send a email to kib@ to ask about it), and my sce­nario is not the same as the one which is described in the mail, but because of this I decid­ed to switch one of the two UFS mir­rors to ZFS.

The first boot into the ZFS caused again a reboot after some min­utes (I do not know if it was because of a mem­o­ry exhaust­ed pan­ic, or because of a dead­lock), but as I did not tune the ker­nel for ZFS I am tempt­ed to believe that I should not count that. Now, after tun­ing the ker­nel (increas­ing the kmem_size to 700M, no prefetch­ing, lim­it­ing the ARC to 40M) it is up since near­ly 2h (as of this writ­ting… cross­ing fin­gers). Before it was not able to sur­vive more than some min­utes with just the jail for the mails up. Now I not only have the mail-jail up, but also the jail for the blog (one jail still dis­abled, but I will take care about that after this post).

I do not know if only increas­ing the kmem_size would have helped with the prob­lem, but as I was test­ing a GENERIC ker­nel + gmir­ror mod­ule in the begin­ning, I expect­ed that the auto-tuning of this val­ue should have been enough for such a sim­ple set­up (2GB RAM, 2 disks with 3 par­ti­tions each, one par­ti­tion pair for root, one for swap, one for the jails).

I hope that I sta­bi­lized the sys­tem now. It may be the case that I will test some patch­es in case some­one comes up with some­thing, so do not be sur­prised if the blog and email to me is a lit­tle bit flaky.

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Back from hol­i­day: mail-stats

After two weeks of hol­i­day I have about 5.400 emails (about 51 MB, down­loaded and fil­tered in 3h). Split up this is:

  • 2763 from FreeB­SD mail­inglists
  • 320 SPAM (101 false pos­i­tives, most­ly FreeB­SD relat­ed… I should have a look at this and take appro­pri­ate actions)
  • 115 in the nor­mal inbox = per­son­al + not fil­tered emails (18 false neg­a­tive SPAM)
  • 16 post­mas­ter relat­ed, e.g. bounces from forged SPAM, 4 of them are not SPAM bounces but valid mails…
  • 114 secu­ri­ty relat­ed (Bug­traq, …)
  • 220 sta­tus mes­sages (e.g. FreeB­SD peri­od­ic mails from var­i­ous sys­tems)
  • the rest is var­i­ous oth­er (fil­tered away) mails

It will take a while until I had a look at them…

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