Date: Mon, 14 Mar 2011 11:38:15 +0100 From: Fabien Thomas <fabien.thomas@netasq.com> To: freebsd-current@freebsd.org Subject: Deadlock on stable fixed on head Message-ID: <A29B03EE-CBEB-48F7-A31F-0BE8FB29FDF1@netasq.com>
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I'm debugging a deadlock on FreeBSD that is not on head but on 7.3, 8.2...
Maybe someone will have an idea on what patch fixed it.
Context:
1 - On a UP machine (Multicore without SMP option or UP with SMP).
2 - When using device apic (more on this later)
3 - Using DEVICE_POLLING (more on this later)
4- HZ set to 2000
Launching a CPU intensive task freeze the box (burnP6 from cpuburn port)
nearly 100% chance of success.
This can be reproduced on very different HW so it is software related.
Reproduced on i386 / amd64.
Current analysis status:
1 - having >1 CPU and SMP enabled avoid the deadlock
2 - apic enable the problem when using critical_exit (using isa/clock does
not have critical_exit and then works)
3 - this is not the polling itself but the scheduling of the thread only
4 - no idea
So to sum up it seems related to a scheduling issue.
I've got some info from a 8.2 that can enter ddb (7.3 will not enter ddb) [1]
If someone have an idea / fixed something related, etc... tell me :)
[1] http://people.freebsd.org/~fabient/burnP6_deadlock.txt
--
Fabien Thomas
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