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Re: [Qemu-devel] [PULL 11/24] tcg: enable thread-per-vCPU
From: |
Laurent Vivier |
Subject: |
Re: [Qemu-devel] [PULL 11/24] tcg: enable thread-per-vCPU |
Date: |
Mon, 13 Mar 2017 15:03:17 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.7.0 |
Le 27/02/2017 à 15:38, Alex Bennée a écrit :
>
> Laurent Vivier <address@hidden> writes:
>
>> Le 24/02/2017 à 12:20, Alex Bennée a écrit :
>>> There are a couple of changes that occur at the same time here:
>>>
>>> - introduce a single vCPU qemu_tcg_cpu_thread_fn
>>>
>>> One of these is spawned per vCPU with its own Thread and Condition
>>> variables. qemu_tcg_rr_cpu_thread_fn is the new name for the old
>>> single threaded function.
>>>
>>> - the TLS current_cpu variable is now live for the lifetime of MTTCG
>>> vCPU threads. This is for future work where async jobs need to know
>>> the vCPU context they are operating in.
>>>
>>> The user to switch on multi-thread behaviour and spawn a thread
>>> per-vCPU. For a simple test kvm-unit-test like:
>>>
>>> ./arm/run ./arm/locking-test.flat -smp 4 -accel tcg,thread=multi
>>>
>>> Will now use 4 vCPU threads and have an expected FAIL (instead of the
>>> unexpected PASS) as the default mode of the test has no protection when
>>> incrementing a shared variable.
>>>
>>> We enable the parallel_cpus flag to ensure we generate correct barrier
>>> and atomic code if supported by the front and backends. This doesn't
>>> automatically enable MTTCG until default_mttcg_enabled() is updated to
>>> check the configuration is supported.
>>
>> This commit breaks linux-user mode:
>>
>> debian-8 with qemu-ppc on x86_64 with ltp-full-20170116
>>
>> cd /opt/ltp
>> ./runltp -p -l "qemu-$(date +%FT%T).log" -f /opt/ltp/runtest/syscalls -s
>> setgroups03
>>
>> setgroups03 1 TPASS : setgroups(65537) fails, Size is >
>> sysconf(_SC_NGROUPS_MAX), errno=22
>> qemu-ppc: /home/laurent/Projects/qemu/include/qemu/rcu.h:89:
>> rcu_read_unlock: Assertion `p_rcu_reader->depth != 0' failed.
>> qemu-ppc: /home/laurent/Projects/qemu/include/qemu/rcu.h:89:
>> rcu_read_unlock: Assertion `p_rcu_reader->depth != 0' failed.
>> qemu-ppc: /home/laurent/Projects/qemu/include/qemu/rcu.h:89:
>> rcu_read_unlock: Assertion `p_rcu_reader->depth != 0' failed.
>> ...
>
> Interesting. I can only think the current_cpu change has broken it
> because most of the changes in this commit affect softmmu targets only
> (linux-user has its own run loop).
>
> Thanks for the report - I'll look into it.
After:
95b0eca Merge remote-tracking branch
'remotes/stsquad/tags/pull-mttcg-fixups-090317-1' into staging
[Tested with my HEAD on:
b1616fe Merge remote-tracking branch
'remotes/famz/tags/docker-pull-request' into staging]
I have now:
<<<test_start>>>
tag=setgroups03 stime=1489413401
cmdline="setgroups03"
contacts=""
analysis=exit
<<<test_output>>>
**
ERROR:/home/laurent/Projects/qemu/cpu-exec.c:656:cpu_exec: assertion
failed: (cpu == current_cpu)
**
Laurent
- Re: [Qemu-devel] [PULL 11/24] tcg: enable thread-per-vCPU,
Laurent Vivier <=