On Thu, 25 Jul 2013 13:56:47 -0400, Salam Farhat said: > When the guest OS freezes I get the following messages seen below. I would > like to know what is a good approach for debugging this issue. I am not > sure what a process stall is. Is that a deadlock? > > > [ 780.357876] BUG: soft lockup - CPU#0 stuck for 22s! [nautilus:1382] > [ 780.361658] Process nautilus (pid: 1382, ti=dca12000 task=dc837230 task.ti=d) > [ 780.361658] > Stack: > [ 780.361658] Call Trace: > [ 780.361658] Code: 90 b8 43 64 03 c1 b9 40 64 03 c1 e9 49 ff ff ff 90 55 ba 0 > [ 808.356372] BUG: soft lockup - CPU#0 stuck for 22s! That's probably not a deadlock. That's code stuck in an infinite loop, probably while running in a non-interruptible state. Too bad we didn't get a stack dump out of it, that would tell us what code is hung in a loop. For debugging deadlocks, turning on CONFIG_PROVE_LOCKING=y in the .config is the best bet - that will fire an alert not only when the kernel *does* lock up, but also if there's even a *possible* deadlock (for instance, if one section takes 2 locks in the order A B, it will trigger if it ever spots another chunk of code taking B and then A - even if that doesn't actually trigger a deadlock because neither lock is held at the time).
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