Re: [Qemu-devel] qtest hang in /x86_64/ahci/io/ncq/simple (ppc64 host)

[John Snow <jsnow@redhat.com>]

On 07/06/2015 11:35 AM, Peter Maydell wrote:
> I'm seeing a qtest hang in the /x86_64/ahci/io/ncq/simple
> test case. It looks like QEMU is running OK, but the qtest test
> is busy-looping in ahci_command_wait():
> 
> #0  ahci_command_wait (ahci=0x1003f3f9400, cmd=0x1003f401810) at
> /home/pm215/qemu/tests/libqos/ahci.c:929
> #1  0x000000001001ba10 in ahci_command_issue (ahci=0x1003f3f9400,
> cmd=0x1003f401810)
>     at /home/pm215/qemu/tests/libqos/ahci.c:937
> #2  0x0000000010019f18 in ahci_guest_io (ahci=0x1003f3f9400, port=5
> '\005', ide_cmd=97 'a', buffer=1097728,
>     bufsize=4096, sector=0) at /home/pm215/qemu/tests/libqos/ahci.c:632
> #3  0x000000001000b640 in ahci_test_io_rw_simple (ahci=0x1003f3f9400,
> bufsize=4096, sector=0, read_cmd=
>     96 '`', write_cmd=97 'a') at /home/pm215/qemu/tests/ahci-test.c:886
> #4  0x000000001000d434 in test_ncq_simple () at
> /home/pm215/qemu/tests/ahci-test.c:1439
> #5  0x00000080753db01c in 000000ca.plt_call.strncasecmp@@GLIBC_2.3+0
> () from /lib64/libglib-2.0.so.0
> #6  0x00000080753db1f8 in 000000ca.plt_call.strncasecmp@@GLIBC_2.3+0
> () from /lib64/libglib-2.0.so.0
> #7  0x00000080753db1f8 in 000000ca.plt_call.strncasecmp@@GLIBC_2.3+0
> () from /lib64/libglib-2.0.so.0
> #8  0x00000080753db1f8 in 000000ca.plt_call.strncasecmp@@GLIBC_2.3+0
> () from /lib64/libglib-2.0.so.0
> #9  0x00000080753db1f8 in 000000ca.plt_call.strncasecmp@@GLIBC_2.3+0
> () from /lib64/libglib-2.0.so.0
> #10 0x00000080753db6c0 in .g_test_run_suite () from /lib64/libglib-2.0.so.0
> #11 0x00000080753db778 in .g_test_run () from /lib64/libglib-2.0.so.0
> #12 0x000000001000de70 in main (argc=1, argv=0x3fffeeb5a578) at
> /home/pm215/qemu/tests/ahci-test.c:1703
> 
> If you singlestep, we just loop round and round. Presumably
> the condition we're expecting just never becomes true.
> 
> I've only seen this on a ppc64 host system; my x86-64 and arm
> 'make check' runs have been fine. Have you tested your AHCI
> qtest code on a big endian system? (Not necessarily the
> problem, Paolo also said he'd seen an intermittent failure
> in one of these ahci tests on an x86 host. But the ppc fail
> seems to be reliably always on the same test.)
> 
> thanks
> -- PMM
> 

I'll take a look. More than possible there's a race in the wait
conditional that I have just never seen before.

I tweaked it a little recently to wait on both NCQ and traditional
completion, but it doesn't have a timeout or anything. I'll go ahead and
fix that while I'm here.

Should be something simple, hopefully.

--js