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Date: Wed, 18 Jul 2012 18:23:34 -0300
From: Marcelo Tosatti <mtosatti@redhat.com>
To: Alex Williamson <alex.williamson@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>, Gleb Natapov <gleb@redhat.com>,
        avi@redhat.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
        jan.kiszka@siemens.com
Subject: Re: [PATCH v5 1/4] kvm: Extend irqfd to support level interrupts
Message-ID: <20120718212334.GA20327@amt.cnet>
References: <20120718114844.GH26120@redhat.com>
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On Wed, Jul 18, 2012 at 02:28:34PM -0600, Alex Williamson wrote:
> > turn on lockdep to remember why I couldn't sleep there.
> 
> switching to a mutex results in:
> 
> BUG: sleeping function called from invalid context at kernel/mutex.c:269
> in_atomic(): 1, irqs_disabled(): 0, pid: 30025, name: qemu-system-x86
> INFO: lockdep is turned off.
> Pid: 30025, comm: qemu-system-x86 Not tainted 3.5.0-rc4+ #109
> Call Trace:
>  [<ffffffff81088425>] __might_sleep+0xf5/0x130
>  [<ffffffff81564c6f>] mutex_lock_nested+0x2f/0x60
>  [<ffffffffa07db7d5>] eoifd_event+0x25/0x70 [kvm]
>  [<ffffffffa07daea4>] kvm_notify_acked_irq+0xa4/0x140 [kvm]
>  [<ffffffffa07dae2a>] ? kvm_notify_acked_irq+0x2a/0x140 [kvm]
>  [<ffffffffa07d9bb4>] kvm_ioapic_update_eoi+0x84/0xf0 [kvm]
>  [<ffffffffa0806c43>] apic_set_eoi+0x123/0x130 [kvm]
>  [<ffffffffa0806fd8>] apic_reg_write+0x388/0x670 [kvm]
>  [<ffffffffa07eb03c>] ? vcpu_enter_guest+0x32c/0x740 [kvm]
>  [<ffffffffa0807481>] kvm_lapic_set_eoi+0x21/0x30 [kvm]
>  [<ffffffffa04ba3f9>] handle_apic_access+0x69/0x80 [kvm_intel]
>  [<ffffffffa04ba02a>] vmx_handle_exit+0xaa/0x260 [kvm_intel]

Its RCU from ack notifiers, OK.