linux-kernel - Re: [syzbot] INFO: task hung in synchronize

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Date:   Tue, 10 May 2022 15:50:57 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        syzbot <syzbot+0c6da80218456f1edc36@...kaller.appspotmail.com>
Cc:     akpm@...ux-foundation.org, davem@...emloft.net, jhs@...atatu.com,
        jiri@...nulli.us, kvm@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        mingo@...e.hu, mlevitsk@...hat.com, netdev@...r.kernel.org,
        peterz@...radead.org, syzkaller-bugs@...glegroups.com,
        tglx@...utronix.de, vinicius.gomes@...el.com,
        viro@...iv.linux.org.uk, xiyou.wangcong@...il.com
Subject: Re: [syzbot] INFO: task hung in synchronize_rcu (3)

On 5/10/22 15:45, Sean Christopherson wrote:
>>
>>      KVM: x86: Don't re-acquire SRCU lock in complete_emulated_io()
>>
>> bisection log:https://syzkaller.appspot.com/x/bisect.txt?x=16dc2e49f00000
>> start commit:   ea4424be1688 Merge tag 'mtd/fixes-for-5.17-rc8' of git://g..
>> git tree:       upstream
>> kernel config:https://syzkaller.appspot.com/x/.config?x=442f8ac61e60a75e
>> dashboard link:https://syzkaller.appspot.com/bug?extid=0c6da80218456f1edc36
>> syz repro:https://syzkaller.appspot.com/x/repro.syz?x=1685af9e700000
>> C reproducer:https://syzkaller.appspot.com/x/repro.c?x=11b09df1700000
>>
>> If the result looks correct, please mark the issue as fixed by replying with:
>>
>> #syz fix: KVM: x86: Don't re-acquire SRCU lock in complete_emulated_io()
>>
>> For information about bisection process see:https://goo.gl/tpsmEJ#bisection
> #syz fix: KVM: x86: Don't re-acquire SRCU lock in complete_emulated_io()
> 

Are you sure? The hang is in synchronize_*rcu* and the testcase is 
unrelated to KVM.  It seems like the testcase is not 100% reproducible.

Paolo