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Groups > linux.kernel > #1544049 > unrolled thread
| Started by | Johanna Abrahamsson <johanna@mjao.org> |
|---|---|
| First post | 2016-12-17 23:30 +0100 |
| Last post | 2016-12-19 10:10 +0100 |
| Articles | 3 — 2 participants |
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[BUG] kernel freeze, rcu_sched self-detected stall on CPU Johanna Abrahamsson <johanna@mjao.org> - 2016-12-17 23:30 +0100
Re: [BUG] kernel freeze, rcu_sched self-detected stall on CPU Davidlohr Bueso <dave@stgolabs.net> - 2016-12-18 17:40 +0100
Re: [BUG] kernel freeze, rcu_sched self-detected stall on CPU Johanna Abrahamsson <johanna@mjao.org> - 2016-12-19 10:10 +0100
| From | Johanna Abrahamsson <johanna@mjao.org> |
|---|---|
| Date | 2016-12-17 23:30 +0100 |
| Subject | [BUG] kernel freeze, rcu_sched self-detected stall on CPU |
| Message-ID | <sPvEl-7do-13@gated-at.bofh.it> |
A bug has been introduced in ipc/sem.c by a patch '[PATCH -next 2/2] ipc/sem: avoid idr tree lookup for interrupted semop' (https://marc.info/?l=linux-kernel&m=147870885903619, commit 370b262c896e5565b271a3ea3abee4d0914ba443). The bug results in a kernel freeze and several "INFO: rcu_sched self-detected stall on CPU". The system becomes unresponsible and has to be rebooted to work again as far as I can tell. My repro case is, hilariously enough, packaging the linux kernel for debian with `make -j8 deb-pkg`. I'm sure a smaller repro case could be constructed, but so far I've had 100% reproducibility from this one. The freeze always occurs at the Makefiles.headerinst part of packaging, after the kernel is built. The bug is present in next-20161124 and linux-next versions going forward from that and has now been merged to linus/master. However, in linus/master it doesn't trigger a bug. This seems to indicate that it only triggers a bug in combination with a commit that is present in next-20161216 but not present in linus/master. I've confirmed that doing `git revert 370b262c896e5565b271a3ea3abee4d0914ba443` on next-20161216 fixes the bug. In all repro cases I've tested on virtual machines with multiple cpu cores running under either Xen or Virtualbox. I will try to investigate this further but as I have limited knowledge of RCU and how the kernel works with semaphores don't expect any miracles :) Best Regards, Johanna Abrahamsson
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| From | Davidlohr Bueso <dave@stgolabs.net> |
|---|---|
| Date | 2016-12-18 17:40 +0100 |
| Message-ID | <sPMFb-2zL-1@gated-at.bofh.it> |
| In reply to | #1544049 |
On Sat, 17 Dec 2016, Johanna Abrahamsson wrote: >I will try to investigate this further but as I have limited knowledge of RCU and how the kernel works with semaphores don't expect any miracles :) Please see if this helps: https://lkml.org/lkml/2016/12/18/79 Thanks, Davidlohr
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| From | Johanna Abrahamsson <johanna@mjao.org> |
|---|---|
| Date | 2016-12-19 10:10 +0100 |
| Message-ID | <sQ27g-5M1-29@gated-at.bofh.it> |
| In reply to | #1544166 |
On Sun, Dec 18, 2016 at 08:32:23AM -0800, Davidlohr Bueso wrote: > Please see if this helps: https://lkml.org/lkml/2016/12/18/79 That does help, thank you! I would never have fixed this myself in reasonable time :) Best Regards, Johanna Abrahamsson
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