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Subject: [Bug 205163] Periodic jobs triggering panics on ZFS host with jails
Date: Thu, 10 Dec 2015 15:28:06 +0000
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=205163

--- Comment #7 from karl@denninger.net ---
(In reply to Andriy Gapon from comment #6)

The predicate that was turned into a dynamic variable was runtime tunable
without any sort of mutex locking; a reasonable perusal of the code disclosed
no reason to not do it.

However, the potential for a sign inversion (which incidentally MIGHT occur in
the base code as well, or to a corner case that could result in a
divide-by-zero) is easily removed (and I have done so and sent the patch to do
so to the reporter, asking if it stops the panics.)

Given the stack trace involved here I don't believe that's implicated as the
cause, however (since the panic is a divide-by-zero trap yet there is no
division by zero evidenced by examination) however, the potential for the stack
to get smashed by an integer division that sets the sign bit and leads to
misbehavior somewhere else in the code is plausible and defending against both
that and the potential for an actual divide-by-zero obviously should be done.

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