From: Sean Christopherson <seanjc@google.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: syzbot <syzbot+0c6da80218456f1edc36@syzkaller.appspotmail.com>,
akpm@linux-foundation.org, davem@davemloft.net, jhs@mojatatu.com,
jiri@resnulli.us, kvm@vger.kernel.org,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
mingo@elte.hu, mlevitsk@redhat.com, netdev@vger.kernel.org,
peterz@infradead.org, syzkaller-bugs@googlegroups.com,
tglx@linutronix.de, vinicius.gomes@intel.com,
viro@zeniv.linux.org.uk, xiyou.wangcong@gmail.com
Subject: Re: [syzbot] INFO: task hung in synchronize_rcu (3)
Date: Tue, 10 May 2022 13:56:51 +0000 [thread overview]
Message-ID: <YnpvI4tgbrEtHBG2@google.com> (raw)
In-Reply-To: <8f24d358-1fbd-4598-1f2d-959b4f8d75fd@redhat.com>
On Tue, May 10, 2022, Paolo Bonzini wrote:
> 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.
Ugh, syzbot seems to have bundled multiple unrelated errors together. The splat
that comes up first on the dashboard is definitely the KVM bug:
INFO: task syz-executor500:19706 blocked for more than 143 seconds.
Not tainted 5.17.0-rc7-syzkaller-00020-gea4424be1688 #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor500 state:D stack:27048 pid:19706 ppid: 3644 flags:0x00000004
Call Trace:
<TASK>
context_switch kernel/sched/core.c:4995 [inline]
__schedule+0xa94/0x4910 kernel/sched/core.c:6304
schedule+0xd2/0x260 kernel/sched/core.c:6377
schedule_timeout+0x1db/0x2a0 kernel/time/timer.c:1857
do_wait_for_common kernel/sched/completion.c:85 [inline]
__wait_for_common+0x2af/0x360 kernel/sched/completion.c:106
__synchronize_srcu+0x1f2/0x290 kernel/rcu/srcutree.c:930
kvm_swap_active_memslots+0x410/0x800 arch/x86/kvm/../../../virt/kvm/kvm_main.c:1473
kvm_activate_memslot arch/x86/kvm/../../../virt/kvm/kvm_main.c:1595 [inline]
kvm_create_memslot arch/x86/kvm/../../../virt/kvm/kvm_main.c:1660 [inline]
kvm_set_memslot+0xa67/0x1010 arch/x86/kvm/../../../virt/kvm/kvm_main.c:1772
__kvm_set_memory_region+0xf02/0x11f0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:1914
kvm_set_memory_region arch/x86/kvm/../../../virt/kvm/kvm_main.c:1927 [inline]
kvm_vm_ioctl_set_memory_region arch/x86/kvm/../../../virt/kvm/kvm_main.c:1939 [inline]
kvm_vm_ioctl+0x51a/0x22c0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:4492
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:874 [inline]
__se_sys_ioctl fs/ioctl.c:860 [inline]
__x64_sys_ioctl+0x193/0x200 fs/ioctl.c:860
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
But there are multiple other errors that are indeed not the KVM bug.
prev parent reply other threads:[~2022-05-10 14:34 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <000000000000402c5305ab0bd2a2@google.com>
2020-07-25 5:11 ` INFO: task hung in synchronize_rcu (3) syzbot
2022-05-10 8:51 ` [syzbot] " syzbot
2022-05-10 13:45 ` Sean Christopherson
2022-05-10 13:50 ` Paolo Bonzini
2022-05-10 13:56 ` Sean Christopherson [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=YnpvI4tgbrEtHBG2@google.com \
--to=seanjc@google.com \
--cc=akpm@linux-foundation.org \
--cc=davem@davemloft.net \
--cc=jhs@mojatatu.com \
--cc=jiri@resnulli.us \
--cc=kvm@vger.kernel.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@elte.hu \
--cc=mlevitsk@redhat.com \
--cc=netdev@vger.kernel.org \
--cc=pbonzini@redhat.com \
--cc=peterz@infradead.org \
--cc=syzbot+0c6da80218456f1edc36@syzkaller.appspotmail.com \
--cc=syzkaller-bugs@googlegroups.com \
--cc=tglx@linutronix.de \
--cc=vinicius.gomes@intel.com \
--cc=viro@zeniv.linux.org.uk \
--cc=xiyou.wangcong@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).