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Date: Wed, 08 Aug 2012 11:41:46 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 11/15] lock: introduce global lock for
	device tree
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To: Liu Ping Fan <qemulist@gmail.com>
Cc: kvm@vger.kernel.org, Jan Kiszka <jan.kiszka@siemens.com>, Marcelo Tosatti <mtosatti@redhat.com>, qemu-devel@nongnu.org, Blue Swirl <blauwirbel@gmail.com>, Avi Kivity <avi@redhat.com>, Anthony Liguori <anthony@codemonkey.ws>, Stefan Hajnoczi <stefanha@gmail.com>, =?ISO-8859-15?Q?Andreas_F=E4rber?= <afaerber@suse.de>

Il 08/08/2012 08:25, Liu Ping Fan ha scritto:
> From: Liu Ping Fan <pingfank@linux.vnet.ibm.com>
> 
> Signed-off-by: Liu Ping Fan <pingfank@linux.vnet.ibm.com>
> ---
>  cpus.c      |   12 ++++++++++++
>  main-loop.h |    3 +++
>  2 files changed, 15 insertions(+), 0 deletions(-)
> 
> diff --git a/cpus.c b/cpus.c
> index b182b3d..a734b36 100644
> --- a/cpus.c
> +++ b/cpus.c
> @@ -611,6 +611,7 @@ static void qemu_tcg_init_cpu_signals(void)
>  }
>  #endif /* _WIN32 */
>  
> +QemuMutex qemu_device_tree_mutex;
>  QemuMutex qemu_global_mutex;
>  static QemuCond qemu_io_proceeded_cond;
>  static bool iothread_requesting_mutex;
> @@ -634,6 +635,7 @@ void qemu_init_cpu_loop(void)
>      qemu_cond_init(&qemu_work_cond);
>      qemu_cond_init(&qemu_io_proceeded_cond);
>      qemu_mutex_init(&qemu_global_mutex);
> +    qemu_mutex_init(&qemu_device_tree_mutex);
>  
>      qemu_thread_get_self(&io_thread);
>  }
> @@ -911,6 +913,16 @@ void qemu_mutex_unlock_iothread(void)
>      qemu_mutex_unlock(&qemu_global_mutex);
>  }
>  
> +void qemu_lock_devtree(void)
> +{
> +    qemu_mutex_lock(&qemu_device_tree_mutex);
> +}
> +
> +void qemu_unlock_devtree(void)
> +{
> +    qemu_mutex_unlock(&qemu_device_tree_mutex);
> +}

We don't need the wrappers.  They are there for the big lock just
because TCG needs extra work for iothread_requesting_mutex.

Paolo

>  static int all_vcpus_paused(void)
>  {
>      CPUArchState *penv = first_cpu;
> diff --git a/main-loop.h b/main-loop.h
> index dce1cd9..17e959a 100644
> --- a/main-loop.h
> +++ b/main-loop.h
> @@ -353,6 +353,9 @@ void qemu_mutex_lock_iothread(void);
>   */
>  void qemu_mutex_unlock_iothread(void);
>  
> +void qemu_lock_devtree(void);
> +void qemu_unlock_devtree(void);
> +
>  /* internal interfaces */
>  
>  void qemu_fd_register(int fd);
>