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Date: Wed, 10 Sep 2014 09:46:21 +0200
Message-ID: <CA+i3ByKkCAJ8wc9-jvQxd_f3CdACihkgHSoHJZ1KtgxogH6_oA@mail.gmail.com>
Subject: subr_witness.c "rm_spinlock" and "smp rendezvous" wrong declaration
 order
From: Philippe Jalaber <pjalaber@gmail.com>
To: freebsd-hackers@freebsd.org
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Hello there,

I have been playing with SMP and witness and looking at subr_witness.c. I
suspect there is a bug in the declaration order of locks "rm_spinlock" and
"smp rendezvous". It leads witness to fire a wrong LOR in SMP.

Details: _rm_wlock in kern/kern_rmlock.c calls smp_rendezvous_cpus who
locks smp_ipi_mtx then calls smp_rendezvous_action who calls rm_cleanIPI
who locks rm_spinlock.

So "smp_rendezvous" should be declared before "rm_spinlock" in
subr_witness.c

Thanks for reading me,
Philippe