Re: [Qemu-devel] question： I found a bug which will lead to qemu crash

[Eric Blake <eblake@redhat.com>]

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On 09/12/2017 06:37 AM, Kevin Wolf wrote:
> Am 12.09.2017 um 13:17 hat WangJie (Captain) geschrieben:
>> Hi, Kevin.
>>
>> I found a bug about qemu-kvm(version 2.7.0-rc0 adn 2.8.1). but qemu 2.6.0 and current master is OK.
>> So I git-bisect the master branch，and I found the patch you commited (block: Decouple throttling from BlockDriverState) lead the bug into qemu.
>>
>> The patch which lead the bug into qemu: (https://github.com/qemu/qemu/commit/7ca7f0f6db1fedd28d490795d778cf23979a2aa7#diff-ea36ba0f79150cc299732696a069caba)
>>
>> Because the current master is OK. So I think you had fixed it , can you tell me which patch fixed the bug?        Thank you :>
> 
> I can't tell offhand which fix this was, but you can use 'git bisect'
> not only to find which commit introduced the bug, but also to find the
> fix. You just bisect between a broken commit and master, and then use
> the reversed meaning of 'good' and 'bad' (i.e. 'good' means that the bug
> is still there, 'bad' means it is already fixed).

That can be mentally confusing; with new-enough git, you can also use:

git bisect start --term-old=buggy --term-new=fixed

at which point, you can then say 'git bisect buggy' or 'git bisect
fixed' according to whether the bug is still present on a given
compilation, without having to remember which direction good/bad means.
There's also 'git bisect terms' to remind you what you chose.


-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org


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