Re: [Qemu-devel] [PATCH 1/2] CPUArchState: introduce per-cpu lock

[Andreas Färber]

Am 24.06.2012 16:02, schrieb liu ping fan:
> On Fri, Jun 22, 2012 at 8:55 PM, Andreas Färber <address@hidden> wrote:
>> Am 21.06.2012 17:06, schrieb Liu Ping Fan:
>>> introduce a lock for per-cpu to protect agaist accesing from
>>> other vcpu thread.
>>>
>>> Signed-off-by: Liu Ping Fan <address@hidden>
>>> ---
>>>  cpu-defs.h  |    2 ++
>>>  cpus.c      |   17 +++++++++++++++++
>>>  main-loop.h |    3 +++
>>>  3 files changed, 22 insertions(+), 0 deletions(-)
>>>
>>> diff --git a/cpu-defs.h b/cpu-defs.h
>>> index f49e950..7305822 100644
>>> --- a/cpu-defs.h
>>> +++ b/cpu-defs.h
>>> @@ -30,6 +30,7 @@
>>>  #include "osdep.h"
>>>  #include "qemu-queue.h"
>>>  #include "targphys.h"
>>> +#include "qemu-thread-posix.h"
>>>
>>>  #ifndef TARGET_LONG_BITS
>>>  #error TARGET_LONG_BITS must be defined before including this header
>>> @@ -220,6 +221,7 @@ typedef struct CPUWatchpoint {
>>>      CPU_COMMON_THREAD                                                   \
>>>      struct QemuCond *halt_cond;                                         \
>>>      int thread_kicked;                                                  \
>>> +    struct QemuMutex *cpu_lock;                                         \
>>>      struct qemu_work_item *queued_work_first, *queued_work_last;        \
>>>      const char *cpu_model_str;                                          \
>>>      struct KVMState *kvm_state;                                         \
>>
>> Please don't add stuff to CPU_COMMON. Instead add to CPUState in
>> qom/cpu.c. The QOM CPUState part 4 series moves many of those fields there.

My mistake: The struct to add to is in include/qemu/cpu.h obviously.

>>
> Ok, thanks.
>>> diff --git a/cpus.c b/cpus.c
>>> index b182b3d..554f7bc 100644
>>> --- a/cpus.c
>>> +++ b/cpus.c
>>> @@ -735,6 +735,7 @@ static void *qemu_kvm_cpu_thread_fn(void *arg)
>>>      env->thread_id = qemu_get_thread_id();
>>>      cpu_single_env = env;
>>>
>>> +
>>
>> Stray whitespace addition.
>>
>>>      r = kvm_init_vcpu(env);
>>>      if (r < 0) {
>>>          fprintf(stderr, "kvm_init_vcpu failed: %s\n", strerror(-r));
>>> @@ -891,6 +892,20 @@ int qemu_cpu_is_self(void *_env)
>>>      return qemu_thread_is_self(env->thread);
>>>  }
>>>
>>> +void qemu_mutex_lock_cpu(void *_env)
>>> +{
>>> +    CPUArchState *env = _env;
>>> +
>>> +    qemu_mutex_lock(env->cpu_lock);
>>> +}
>>> +
>>> +void qemu_mutex_unlock_cpu(void *_env)
>>> +{
>>> +    CPUArchState *env = _env;
>>> +
>>> +    qemu_mutex_unlock(env->cpu_lock);
>>> +}
>>> +
>>
>> I don't like these helpers. For one, you are using void * arguments and
>> casting them, for another you are using CPUArchState at all. With my
>> suggestion above these can be CPUState *cpu.
>>
> For using it in apic.c, we need to hide the  CPUArchState structure

CPUState serves to hide CPUArchState, with added type safety. :)

Regards,
Andreas

>>>  void qemu_mutex_lock_iothread(void)
>>>  {
>>>      if (!tcg_enabled()) {
>>> @@ -1027,6 +1042,8 @@ void qemu_init_vcpu(void *_env)
>>>      env->nr_cores = smp_cores;
>>>      env->nr_threads = smp_threads;
>>>      env->stopped = 1;
>>> +    env->cpu_lock = g_malloc0(sizeof(QemuMutex));
>>> +    qemu_mutex_init(env->cpu_lock);
>>
>> Are you sure this is not needed for linux-user/bsd-user? If not needed,
>> then the field should be #ifdef'ed in the struct to assure that.
>> Otherwise this function is never called and you need to move the
>> initialization to the initfn in qom/cpu.c and then should also clean it
>> up in a finalizer.
>>
> It is not needed for linux-user/bsd-user. I will use the macro,
> 
> Thanks and regards,
> pingfan

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