Re: [Xen-devel] Creating a vm with a non-existent /dev/mapper/ tap2 device effectively hangs dom0 system

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Thu, Jul 28, 2011 at 12:00:53PM -0700, Nathan March wrote:
> On 7/27/2011 4:29 PM, Nathan March wrote:
> >Have an interesting one here, originally found on xen 4.1.0 but
> >just upgraded to xen 4.1.1 and it's still here.
> >
> >Creating a VM with a tap2 device pointed at /dev/mapper/something,
> >when that device doesn't exist, causes the tapdisk2 process to go
> >into D mode and also manages to take out any process that queries
> >it.

Daniel, any ideas?
[edit: Asked Nathan to pull latest Jermey's with your blktap fix]
> >
> 
> This also happens on proper shutdown of a VM, so I must have done
> something crazy to the setup here since other people haven't been
> complaining. If I start a VM, strace it's tapdisk2 and then send the
> VM a shutdown, the strace shows tapdisk2 hanging here:
> 
> 12037 gettimeofday({1311879426, 739622}, NULL) = 0
> 12037 gettimeofday({1311879426, 739717}, NULL) = 0
> 12037 select(8, [3 4 7], [], [], {600, 0}) = 1 (in [3], left {599, 993029})
> 12037 gettimeofday({1311879426, 746896}, NULL) = 0
> 12037 accept(3, 0, NULL)                = 6
> 12037 gettimeofday({1311879426, 747079}, NULL) = 0
> 12037 gettimeofday({1311879426, 747169}, NULL) = 0
> 12037 gettimeofday({1311879426, 747257}, NULL) = 0
> 12037 select(8, [3 4 6 7], [], [], {600, 0}) = 1 (in [6], left {599,
> 999948})
> 12037 gettimeofday({1311879426, 747544}, NULL) = 0
> 12037 select(7, [6], NULL, NULL, {2, 0}) = 1 (in [6], left {1, 999998})
> 12037 read(6, 
> "\r\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0",
> 280) = 280
> 12037 gettimeofday({1311879426, 747932}, NULL) = 0
> 12037 sendto(5, "<30>Jul 28 11:57:06 tapdisk2[12036]: received
> 'close' message (uuid = 0)\n", 73, MSG_NOSIGNAL, NULL, 0) = 73
> 12037 close(8)                          = 0
> 12037 gettimeofday({1311879426, 749118}, NULL) = 0
> 12037 sendto(5, "<30>Jul 28 11:57:06 tapdisk2[12036]: closed image
> /dev/mapper/nathanxenuk1 (0 users, state: 0x00000000, type: 0)\n",
> 113, MSG_NOSIGNAL, NULL, 0) = 113
> 12037 gettimeofday({1311879426, 749536}, NULL) = 0
> 12037 sendto(5, "<30>Jul 28 11:57:06 tapdisk2[12036]: sending 'close
> response' message (uuid = 0)\n", 81, MSG_NOSIGNAL, NULL, 0) = 81
> 12037 select(7, NULL, [6], NULL, {2, 0}) = 1 (out [6], left {1, 999998})
> 12037 write(6, 
> "\16\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0",
> 280) = 280
> 12037 close(6)                          = 0
> 12037 gettimeofday({1311879426, 750295}, NULL) = 0
> 12037 gettimeofday({1311879426, 750384}, NULL) = 0
> 12037 select(8, [3 4 7], [], [], {600, 0}) = 1 (in [3], left {599, 999936})
> 12037 gettimeofday({1311879426, 750690}, NULL) = 0
> 12037 accept(3, 0, NULL)                = 6
> 12037 gettimeofday({1311879426, 750801}, NULL) = 0
> 12037 gettimeofday({1311879426, 750854}, NULL) = 0
> 12037 gettimeofday({1311879426, 750905}, NULL) = 0
> 12037 select(8, [3 4 6 7], [], [], {600, 0}) = 1 (in [6], left {599,
> 999946})
> 12037 gettimeofday({1311879426, 751085}, NULL) = 0
> 12037 select(7, [6], NULL, NULL, {2, 0}) = 1 (in [6], left {1, 999998})
> 12037 read(6, 
> "\17\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0",
> 280) = 280
> 12037 gettimeofday({1311879426, 751550}, NULL) = 0
> 12037 sendto(5, "<30>Jul 28 11:57:06 tapdisk2[12036]: received
> 'detach' message (uuid = 0)\n", 74, MSG_NOSIGNAL, NULL, 0) = 74
> 12037 close(7)                          = 0
> 12037 munmap(0x7ffc389d7000, 1445888
> 
> COMMAND    PID USER   FD   TYPE             DEVICE SIZE/OFF   NODE NAME
> tapdisk2 12037 root  cwd    DIR                8,1     4096      2 /
> tapdisk2 12037 root  rtd    DIR                8,1     4096      2 /
> tapdisk2 12037 root  txt    REG                8,1   496268 180124
> /usr/sbin/tapdisk2
> tapdisk2 12037 root  mem    REG                8,1  1412272 268124
> /lib64/libc-2.11.2.so
> tapdisk2 12037 root  mem    REG                8,1   534648 267759
> /lib64/libm-2.11.2.so
> tapdisk2 12037 root  mem    REG                8,1   137732 267539
> /lib64/libpthread-2.11.2.so
> tapdisk2 12037 root  mem    REG                8,1    14512 267757
> /lib64/libdl-2.11.2.so
> tapdisk2 12037 root  mem    REG                8,1   164708 180168
> /usr/lib64/libxenctrl.so.4.0.0
> tapdisk2 12037 root  mem    REG                8,1    18832 267724
> /lib64/libuuid.so.1.3.0
> tapdisk2 12037 root  mem    REG                8,1   410267 180118
> /usr/lib64/libvhd.so.1.0.0
> tapdisk2 12037 root  mem    REG                8,1    88368 268110
> /lib64/libz.so.1.2.3
> tapdisk2 12037 root  mem    REG                8,1    35656 267750
> /lib64/librt-2.11.2.so
> tapdisk2 12037 root  mem    REG                8,1   128416 267762
> /lib64/ld-2.11.2.so
> tapdisk2 12037 root  mem    CHR              251,0           44028
> /dev/xen/blktap-2/blktap0
> tapdisk2 12037 root    0u   CHR                1,3      0t0   1539 /dev/null
> tapdisk2 12037 root    1u   CHR                1,3      0t0   1539 /dev/null
> tapdisk2 12037 root    2u   CHR                1,3      0t0   1539 /dev/null
> tapdisk2 12037 root    3u  unix 0xffff880039c862c0      0t0  44033
> /var/run/blktap-control/ctl12037
> tapdisk2 12037 root    4u  0000                0,8        0   1000
> anon_inode
> tapdisk2 12037 root    5u  unix 0xffff880039cbe840      0t0  44036 socket
> tapdisk2 12037 root    7u   CHR              251,0      0t0  44028
> /dev/xen/blktap-2/blktap0
> tapdisk2 12037 root    8u   BLK              252,0      0t0  36899
> /dev/mapper/nathanxenuk1
> 
> The /dev/mapper devices are coming from a dell md3200i, using
> open-iscsi 2.0.871 and multipath-tools-0.4.9-r2.
> 
> This is using the main xen 4.1.1 release, with jeremy's git dom0
> kernel (2.6.32.43).

Oh, wait. Did you update it to the latest Jeremy pulled in a blktap fix.
> 
> Anyone have any idea what might be happening here?
> 
> - Nathan
> 
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