Re: acquiring duplicate lock of same type: "ftlk"

2009/9/8 Kostik Belousov <kostikbel_at_gmail.com>:
> On Mon, Sep 07, 2009 at 10:15:48PM +0400, pluknet wrote:
>> 2009/8/27 pluknet <pluknet_at_gmail.com>:
>> > Hi.
>> >
>> > Got it on FreeBSD 9.0-CURRENT while been running in Xorg, don't know
>> > where exactly.
>> >
>> > Acquiring duplicate lock of same type: "ftlk"
>> >  1st ftlk _at_ /usr/src/sys/modules/linux/../../compat/linux/linux_futex.c:177
>> >  2nd ftlk _at_ /usr/src/sys/modules/linux/../../compat/linux/linux_futex.c:203
>> > KDB: stack backtrace:
>> > db_trace_self_wrapper(c07fd8ea,ea393b58,c060a145,c05fac1b,c08007b2,...)
>> > at db_trace_self_wrapper+0x26
>> > kdb_backtrace(c05fac1b,c08007b2,c0b49757,c58ead20,ea393bb4,...) at
>> > kdb_backtrace+0x29
>> > _witness_debugger(c08007b2,c0b49793,c0b49757,cb,0,...) at _witness_debugger+0x25
>> > witness_checkorder(c9bba780,9,c0b49757,cb,0,...) at witness_checkorder+0x469
>> > _sx_xlock(c9bba780,0,c0b49757,cb,0,...) at _sx_xlock+0x85
>> > futex_get0(c0609f8c,c09cc7a8,c9ac7764,c09cc7a8,c084df3c,...) at futex_get0+0x116
>> > linux_sys_futex(c9ac76c0,ea393cf8,ea393d18,ea393d1c,c0b4cf40,...) at
>> > linux_sys_futex+0x6f
>> > syscall(ea393d38) at syscall+0x2b4
>> > Xint0x80_syscall() at Xint0x80_syscall+0x20
>> > --- syscall (240, Linux ELF, linux_sys_futex), eip = 0x28799533, esp =
>> > 0xbfbfc0cc, ebp = 0x4000001 ---
>> >
>> >
> From what dchagin_at_ told me, the LOR is unavoidable since he has to
> acquire two sx locks of the same name. On the other hand, second sx lock
> is not visible to any thread except the current one, so the LOR should
> be innocent.
>
>>
>> This time seeing this LOR again but with another one just before.
>> lock order reversal:
>>  1st 0xc75365b8 pseudofs (pseudofs) _at_ /usr/src/sys/kern/vfs_lookup.c:497
>>  2nd 0xc088ea3c allproc (allproc) _at_ /usr/src/sys/kern/kern_proc.c:292
>> KDB: stack backtrace:
>> db_trace_self_wrapper(c07fd8ea,e82148e4,c060a145,c05fac1b,c08008bf,...)
>> at db_trace_self_wrapper+0x26
>> kdb_backtrace(c05fac1b,c08008bf,c58eabe8,c58e30d0,e8214940,...) at
>> kdb_backtrace+0x29
>> _witness_debugger(c08008bf,c088ea3c,c07f981d,c58e30d0,c07f96f0,...) at
>> _witness_debugger+0x25
>> witness_checkorder(c088ea3c,1,c07f96f0,124,0,...) at witness_checkorder+0x839
>> _sx_slock(c088ea3c,0,c07f96f0,124,c73c4980,...) at _sx_slock+0x85
>> pfind(514,c72ba1a0,4,c07f8d78,c5fe1b40,...) at pfind+0x2f
>> pfs_visible(0,0,c07f042d,7c,c7536560,...) at pfs_visible+0x3a
>> pfs_lookup(e8214a40,c082715e,c7536560,c7536560,e8214bf8,...) at pfs_lookup+0x3dd
>> VOP_CACHEDLOOKUP_APV(c0843960,e8214a40,e8214bf8,e8214be4,c73c4e80,...)
>> at VOP_CACHEDLOOKUP_APV+0xc5
>> vfs_cache_lookup(e8214acc,c08087d0,c0875a00,200000,e8214bcc,...) at
>> vfs_cache_lookup+0xd6
>> VOP_LOOKUP_APV(c0843960,e8214acc,e8214bf8,1f1,e8214be4,...) at
>> VOP_LOOKUP_APV+0xe5
>> lookup(e8214bcc,c5fd1800,0,c5,c5ef77f8,...) at lookup+0x63b
>> namei(e8214bcc,c5c1500d,3f3,e8214c20,c5c1500d,...) at namei+0x57f
>> kern_alternate_path(c5fe1b40,c0b4921c,2879f478,0,e8214c74,...) at kern_alternate
>> _path+0x1cd
>> linux_emul_convpath(c5fe1b40,2879f478,0,e8214c74,0,...) at
>> linux_emul_convpath+0x3c
>> linux_open(c5fe1b40,e8214cf8,e8214d18,e8214d1c,c0b4b58c,...) at linux_open+0x41
>> syscall(e8214d38) at syscall+0x2b4
>> Xint0x80_syscall() at Xint0x80_syscall+0x20
>> --- syscall (5, Linux ELF, linux_open), eip = 0x2889115e, esp =
>> 0xbfbfbd1c, ebp = 0xbfbfbd6c ---
>> acquiring duplicate lock of same type: "ftlk"
>> [...]
>>
>> I'm running head from 08/26.
>> There were recent changes in pseudofs. Could it be fixed?
>> Looks like it's connected to running firefox3 with linprocfs (for adobe flash).
>
> The second LOR actually exposes the right order. It would be interesting
> to look up the point where the other order is established.

You would manually patch the witness static table with this order and
the opposite will show, when happening.

Attilio


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