panic in softdep_slowdown()
Gleb Smirnoff
glebius at FreeBSD.org
Wed Jan 28 19:33:20 UTC 2015
On Wed, Jan 28, 2015 at 09:04:42PM +0200, Konstantin Belousov wrote:
K> > I can't see where integer divide fault can happen with stat_flush_threads=1 :(
K>
K> Look at the exact asm instruction which faulted, also look at the registers
K> content.
K>
K> It might be hypervisor bug, after all.
Yes, for me it looks like it. %edx should be one as well as -0x44(%rbp).
0xffffffff80895d43 <softdep_slowdown+435>: mov -0x20(%rbp),%ecx
0xffffffff80895d46 <softdep_slowdown+438>: mov %ecx,%edx
0xffffffff80895d48 <softdep_slowdown+440>: shr $0x1f,%edx
0xffffffff80895d4b <softdep_slowdown+443>: add %edx,%ecx
0xffffffff80895d4d <softdep_slowdown+445>: sar %ecx
0xffffffff80895d4f <softdep_slowdown+447>: mov 0xffffffff80ee24c8,%edx
0xffffffff80895d56 <softdep_slowdown+454>: mov %rax,-0x40(%rbp)
0xffffffff80895d5a <softdep_slowdown+458>: mov %ecx,%eax
0xffffffff80895d5c <softdep_slowdown+460>: mov %edx,-0x44(%rbp)
0xffffffff80895d5f <softdep_slowdown+463>: cltd
0xffffffff80895d60 <softdep_slowdown+464>: mov -0x44(%rbp),%ecx
0xffffffff80895d63 <softdep_slowdown+467>: idiv %ecx
(kgdb) p &stat_flush_threads
$5 = (int *) 0xffffffff80ee24c8
(kgdb) info registers
rax 0x12b86 76678
rbx 0x4 4
rcx 0x0 0
rdx 0x0 0
rsi 0x3e8 1000
rdi 0x99 153
rbp 0xfffffe001eb5f2b0 0xfffffe001eb5f2b0
...
(kgdb) p *(int *)($rbp - 0x44)
$4 = 0
(kgdb) p *(int *)($rbp - 0x40)
$8 = 0
(kgdb) p &max_softdeps_hard
$11 = (int *) 0xfffffe001eb5f290
(kgdb) p (int *)($rbp - 0x20)
$12 = (int *) 0xfffffe001eb5f290
(kgdb) p max_softdeps_hard
$10 = 153357
--
Totus tuus, Glebius.
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