Re: [PATCH v8 02/74] cpu: rename cpu->work_mutex to cpu->lock

["Alex Bennée" <alex.bennee@linaro.org>]

Robert Foley <robert.foley@linaro.org> writes:

> From: "Emilio G. Cota" <cota@braap.org>
>
> This lock will soon protect more fields of the struct. Give
> it a more appropriate name.

Hmm while bisecting to find another problem I found this commit:

  /home/alex/lsrc/qemu.git/hw/core/cpu.c: In function ‘cpu_common_finalize’:
  /home/alex/lsrc/qemu.git/hw/core/cpu.c:383:27: error: incompatible type for argument 1 of ‘qemu_mutex_destroy’
       qemu_mutex_destroy(cpu->lock);
                          ~~~^~~~~~
  In file included from /home/alex/lsrc/qemu.git/include/hw/core/cpu.h:31,
                   from /home/alex/lsrc/qemu.git/hw/core/cpu.c:23:
  /home/alex/lsrc/qemu.git/include/qemu/thread.h:26:36: note: expected ‘QemuMutex *’ {aka ‘struct QemuMutex *’} but argument is of type ‘QemuMutex’ {aka ‘struct QemuMutex’}
   void qemu_mutex_destroy(QemuMutex *mutex);
                           ~~~~~~~~~~~^~~~~
  make: *** [/home/alex/lsrc/qemu.git/rules.mak:69: hw/core/cpu.o] Error 1

which works fine in the final product so I suspect something has slipped
between commits somewhere.

>
> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
> Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
> Signed-off-by: Emilio G. Cota <cota@braap.org>
> Signed-off-by: Robert Foley <robert.foley@linaro.org>
> ---
>  cpus-common.c         | 14 +++++++-------
>  cpus.c                |  4 ++--
>  hw/core/cpu.c         |  4 ++--
>  include/hw/core/cpu.h |  6 ++++--
>  4 files changed, 15 insertions(+), 13 deletions(-)
>
> diff --git a/cpus-common.c b/cpus-common.c
> index 3d659df464..f75cae23d9 100644
> --- a/cpus-common.c
> +++ b/cpus-common.c
> @@ -107,10 +107,10 @@ struct qemu_work_item {
>  
>  static void queue_work_on_cpu(CPUState *cpu, struct qemu_work_item *wi)
>  {
> -    qemu_mutex_lock(&cpu->work_mutex);
> +    qemu_mutex_lock(&cpu->lock);
>      QSIMPLEQ_INSERT_TAIL(&cpu->work_list, wi, node);
>      wi->done = false;
> -    qemu_mutex_unlock(&cpu->work_mutex);
> +    qemu_mutex_unlock(&cpu->lock);
>  
>      qemu_cpu_kick(cpu);
>  }
> @@ -304,15 +304,15 @@ void process_queued_cpu_work(CPUState *cpu)
>  {
>      struct qemu_work_item *wi;
>  
> -    qemu_mutex_lock(&cpu->work_mutex);
> +    qemu_mutex_lock(&cpu->lock);
>      if (QSIMPLEQ_EMPTY(&cpu->work_list)) {
> -        qemu_mutex_unlock(&cpu->work_mutex);
> +        qemu_mutex_unlock(&cpu->lock);
>          return;
>      }
>      while (!QSIMPLEQ_EMPTY(&cpu->work_list)) {
>          wi = QSIMPLEQ_FIRST(&cpu->work_list);
>          QSIMPLEQ_REMOVE_HEAD(&cpu->work_list, node);
> -        qemu_mutex_unlock(&cpu->work_mutex);
> +        qemu_mutex_unlock(&cpu->lock);
>          if (wi->exclusive) {
>              /* Running work items outside the BQL avoids the following deadlock:
>               * 1) start_exclusive() is called with the BQL taken while another
> @@ -328,13 +328,13 @@ void process_queued_cpu_work(CPUState *cpu)
>          } else {
>              wi->func(cpu, wi->data);
>          }
> -        qemu_mutex_lock(&cpu->work_mutex);
> +        qemu_mutex_lock(&cpu->lock);
>          if (wi->free) {
>              g_free(wi);
>          } else {
>              atomic_mb_set(&wi->done, true);
>          }
>      }
> -    qemu_mutex_unlock(&cpu->work_mutex);
> +    qemu_mutex_unlock(&cpu->lock);
>      qemu_cond_broadcast(&qemu_work_cond);
>  }
> diff --git a/cpus.c b/cpus.c
> index 151abbc04c..71bd2f5d55 100644
> --- a/cpus.c
> +++ b/cpus.c
> @@ -100,9 +100,9 @@ static inline bool cpu_work_list_empty(CPUState *cpu)
>  {
>      bool ret;
>  
> -    qemu_mutex_lock(&cpu->work_mutex);
> +    qemu_mutex_lock(&cpu->lock);
>      ret = QSIMPLEQ_EMPTY(&cpu->work_list);
> -    qemu_mutex_unlock(&cpu->work_mutex);
> +    qemu_mutex_unlock(&cpu->lock);
>      return ret;
>  }
>  
> diff --git a/hw/core/cpu.c b/hw/core/cpu.c
> index 2fc6aa2159..bc0416829a 100644
> --- a/hw/core/cpu.c
> +++ b/hw/core/cpu.c
> @@ -367,7 +367,7 @@ static void cpu_common_initfn(Object *obj)
>      cpu->nr_cores = 1;
>      cpu->nr_threads = 1;
>  
> -    qemu_mutex_init(&cpu->work_mutex);
> +    qemu_mutex_init(&cpu->lock);
>      QSIMPLEQ_INIT(&cpu->work_list);
>      QTAILQ_INIT(&cpu->breakpoints);
>      QTAILQ_INIT(&cpu->watchpoints);
> @@ -379,7 +379,7 @@ static void cpu_common_finalize(Object *obj)
>  {
>      CPUState *cpu = CPU(obj);
>  
> -    qemu_mutex_destroy(&cpu->work_mutex);
> +    qemu_mutex_destroy(cpu->lock);
>  }
>  
>  static int64_t cpu_common_get_arch_id(CPUState *cpu)
> diff --git a/include/hw/core/cpu.h b/include/hw/core/cpu.h
> index 398b65159e..0b75fdb093 100644
> --- a/include/hw/core/cpu.h
> +++ b/include/hw/core/cpu.h
> @@ -331,7 +331,8 @@ struct qemu_work_item;
>   * @opaque: User data.
>   * @mem_io_pc: Host Program Counter at which the memory was accessed.
>   * @kvm_fd: vCPU file descriptor for KVM.
> - * @work_mutex: Lock to prevent multiple access to @work_list.
> + * @lock: Lock to prevent multiple access to per-CPU fields. Must be acquired
> + *        after the BQL.
>   * @work_list: List of pending asynchronous work.
>   * @trace_dstate_delayed: Delayed changes to trace_dstate (includes all changes
>   *                        to @trace_dstate).
> @@ -375,7 +376,8 @@ struct CPUState {
>      uint64_t random_seed;
>      sigjmp_buf jmp_env;
>  
> -    QemuMutex work_mutex;
> +    QemuMutex lock;
> +    /* fields below protected by @lock */
>      QSIMPLEQ_HEAD(, qemu_work_item) work_list;
>  
>      CPUAddressSpace *cpu_ases;


-- 
Alex Bennée