From mboxrd@z Thu Jan  1 00:00:00 1970
From: Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: kernel 4.4.2: kvm_irq_delivery_to_api /
	rwsem_down_read_failed
Date: Mon, 22 Feb 2016 18:36:05 +0100
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To: Stefan Priebe <s.priebe@profihost.ag>, qemu-devel
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On 20/02/2016 11:44, Stefan Priebe wrote:
> Hi,
> 
> while testing Kernel 4.4.2 and starting 20 Qemu 2.4.1 virtual machines.
> I got those traces and a load of 500 on those system. I was only abler
> to recover by sysrq-trigger.

It seems like something happening at the VM level.  A task took the mm
semaphore and hung everyone else.  Difficult to debug without a core
(and without knowing who held the semaphore).  Sorry.

Paolo


> All traces:
> 
> INFO: task pvedaemon worke:7470 blocked for more than 120 seconds.
> Not tainted 4.4.2+1-ph #1
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> pvedaemon worke D ffff88239c367ca0 0 7470 7468 0x00080000
> ffff88239c367ca0 ffff8840a6232500 ffff8823ed83a500 ffff88239c367c90
> ffff88239c368000 ffff8845f5f070e8 ffff8845f5f07100 0000000000000000
> 00007ffc73b48e58 ffff88239c367cc0 ffffffffb66a4d89 ffff88239c367cf0
> Call Trace:
> [<ffffffffb66a4d89>] schedule+0x39/0x80
> [<ffffffffb66a7447>] rwsem_down_read_failed+0xc7/0x120
> [<ffffffffb63cb594>] call_rwsem_down_read_failed+0x14/0x30
> [<ffffffffb66a6af7>] ? down_read+0x17/0x20
> [<ffffffffb617b99e>] __access_remote_vm+0x3e/0x1c0
> [<ffffffffb63cb594>] ? call_rwsem_down_read_failed+0x14/0x30
> [<ffffffffb6181d5f>] access_remote_vm+0x1f/0x30
> [<ffffffffb623212e>] proc_pid_cmdline_read+0x16e/0x4f0
> [<ffffffffb611a4cc>] ? acct_account_cputime+0x1c/0x20
> [<ffffffffb61c8348>] __vfs_read+0x18/0x40
> [<ffffffffb61c94fe>] vfs_read+0x8e/0x140
> [<ffffffffb61c95ff>] SyS_read+0x4f/0xa0
> [<ffffffffb66a892e>] entry_SYSCALL_64_fastpath+0x12/0x71
> INFO: task pvestatd:7633 blocked for more than 120 seconds.
> Not tainted 4.4.2+1-ph #1
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> pvestatd D ffff88239f16fd40 0 7633 1 0x00080000
> ffff88239f16fd40 ffff8824e76a8000 ffff8823e5fc2500 ffff8823e5fc2500
> ffff88239f170000 ffff8845f5f070e8 ffff8845f5f07100 ffff8845f5f07080
> 000000000341bf10 ffff88239f16fd60 ffffffffb66a4d89 024000d000000058
> Call Trace:
> [<ffffffffb66a4d89>] schedule+0x39/0x80
> [<ffffffffb66a7447>] rwsem_down_read_failed+0xc7/0x120
> [<ffffffffb63cb594>] call_rwsem_down_read_failed+0x14/0x30
> [<ffffffffb66a6af7>] ? down_read+0x17/0x20
> [<ffffffffb623206c>] proc_pid_cmdline_read+0xac/0x4f0
> [<ffffffffb611a4cc>] ? acct_account_cputime+0x1c/0x20
> [<ffffffffb60b1f23>] ? account_user_time+0x73/0x80
> [<ffffffffb60b249e>] ? vtime_account_user+0x4e/0x70
> [<ffffffffb61c8348>] __vfs_read+0x18/0x40
> [<ffffffffb61c94fe>] vfs_read+0x8e/0x140
> [<ffffffffb61c95ff>] SyS_read+0x4f/0xa0
> [<ffffffffb66a892e>] entry_SYSCALL_64_fastpath+0x12/0x71