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Date: Wed, 30 Sep 2009 15:02:12 -0500
From: Anthony Liguori <anthony@codemonkey.ws>
MIME-Version: 1.0
Subject: Re: [Qemu-devel] [PATCH 1/2] unlock iothread mutex before running
	kvm ioctl
References: <1254162464-20089-1-git-send-email-glommer@redhat.com>
	<1254162464-20089-2-git-send-email-glommer@redhat.com>
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To: Glauber Costa <glommer@redhat.com>
Cc: aliguori@us.ibm.com, qemu-devel@nongnu.org

Glauber Costa wrote:
> From: Glauber Costa <glommer@mothafucka.localdomain>
>
> Without this, kvm will hold the mutex while it issues its run ioctl,
> and never be able to step out of it, causing a deadlock.
>
> Signed-off-by: Glauber Costa <glommer@mothafucka.localdomain>
>   

Breaks the build when !CONFIG_IOTHREAD and needs a new SoB.

> ---
>  kvm-all.c     |    2 ++
>  qemu-common.h |    3 +++
>  vl.c          |    4 ++--
>  3 files changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/kvm-all.c b/kvm-all.c
> index 7dcc553..11f4414 100644
> --- a/kvm-all.c
> +++ b/kvm-all.c
> @@ -605,7 +605,9 @@ int kvm_cpu_exec(CPUState *env)
>          }
>  
>          kvm_arch_pre_run(env, run);
> +        qemu_mutex_unlock_iothread();
>          ret = kvm_vcpu_ioctl(env, KVM_RUN, 0);
> +        qemu_mutex_lock_iothread();
>          kvm_arch_post_run(env, run);
>  
>          if (ret == -EINTR || ret == -EAGAIN) {
> diff --git a/qemu-common.h b/qemu-common.h
> index 12e7dd0..820dd37 100644
> --- a/qemu-common.h
> +++ b/qemu-common.h
> @@ -146,6 +146,9 @@ char *qemu_strndup(const char *str, size_t size);
>  void *get_mmap_addr(unsigned long size);
>  
>  
> +void qemu_mutex_lock_iothread(void);
> +void qemu_mutex_unlock_iothread(void);
> +
>  /* Error handling.  */
>  
>  void QEMU_NORETURN hw_error(const char *fmt, ...)
> diff --git a/vl.c b/vl.c
> index eb01da7..f24a260 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -3640,7 +3640,7 @@ static void qemu_signal_lock(unsigned int msecs)
>      qemu_mutex_unlock(&qemu_fair_mutex);
>  }
>  
> -static void qemu_mutex_lock_iothread(void)
> +void qemu_mutex_lock_iothread(void)
>  {
>      if (kvm_enabled()) {
>          qemu_mutex_lock(&qemu_fair_mutex);
> @@ -3650,7 +3650,7 @@ static void qemu_mutex_lock_iothread(void)
>          qemu_signal_lock(100);
>  }
>  
> -static void qemu_mutex_unlock_iothread(void)
> +void qemu_mutex_unlock_iothread(void)
>  {
>      qemu_mutex_unlock(&qemu_global_mutex);
>  }
>