Re: [PATCH RFC V2 07/10] perf tools: change machine comm_exec type to atomic

[Arnaldo Carvalho de Melo]

Em Sun, Sep 10, 2017 at 07:23:20PM -0700, kan.liang@xxxxxxxxx escreveu:
> From: Kan Liang <kan.liang@xxxxxxxxx>
> 
> In case there are two or more threads want to change it.

Please describe the scenario that made you want to have this in place,
to help in reviewing and to have it documented in this patch commit log.

- Arnaldo
 
> Signed-off-by: Kan Liang <kan.liang@xxxxxxxxx>
> ---
>  tools/perf/util/machine.c | 11 ++++++-----
>  tools/perf/util/machine.h |  2 +-
>  2 files changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
> index 2f1ad29..bbfb9e0 100644
> --- a/tools/perf/util/machine.c
> +++ b/tools/perf/util/machine.c
> @@ -64,8 +64,8 @@ int machine__init(struct machine *machine, const char *root_dir, pid_t pid)
>  
>  	machine->id_hdr_size = 0;
>  	machine->kptr_restrict_warned = false;
> -	machine->comm_exec = false;
>  	machine->kernel_start = 0;
> +	atomic_set(&machine->comm_exec, 0);
>  
>  	memset(machine->vmlinux_maps, 0, sizeof(machine->vmlinux_maps));
>  
> @@ -238,14 +238,15 @@ struct machine *machines__add(struct machines *machines, pid_t pid,
>  
>  void machines__set_comm_exec(struct machines *machines, bool comm_exec)
>  {
> +	int exec = comm_exec ? 1 : 0;
>  	struct rb_node *nd;
>  
> -	machines->host.comm_exec = comm_exec;
> +	atomic_set(&machines->host.comm_exec, exec);
>  
>  	for (nd = rb_first(&machines->guests); nd; nd = rb_next(nd)) {
>  		struct machine *machine = rb_entry(nd, struct machine, rb_node);
>  
> -		machine->comm_exec = comm_exec;
> +		atomic_set(&machine->comm_exec, exec);
>  	}
>  }
>  
> @@ -505,7 +506,7 @@ struct thread *machine__find_thread(struct machine *machine, pid_t pid,
>  struct comm *machine__thread_exec_comm(struct machine *machine,
>  				       struct thread *thread)
>  {
> -	if (machine->comm_exec)
> +	if (atomic_read(&machine->comm_exec))
>  		return thread__exec_comm(thread);
>  	else
>  		return thread__comm(thread);
> @@ -521,7 +522,7 @@ int machine__process_comm_event(struct machine *machine, union perf_event *event
>  	int err = 0;
>  
>  	if (exec)
> -		machine->comm_exec = true;
> +		atomic_set(&machine->comm_exec, 1);
>  
>  	if (dump_trace)
>  		perf_event__fprintf_comm(event, stdout);
> diff --git a/tools/perf/util/machine.h b/tools/perf/util/machine.h
> index 64663eb..fb3c2a2 100644
> --- a/tools/perf/util/machine.h
> +++ b/tools/perf/util/machine.h
> @@ -38,7 +38,7 @@ struct machine {
>  	struct rb_node	  rb_node;
>  	pid_t		  pid;
>  	u16		  id_hdr_size;
> -	bool		  comm_exec;
> +	atomic_t	  comm_exec;
>  	bool		  kptr_restrict_warned;
>  	char		  *root_dir;
>  	struct threads    threads[THREADS__TABLE_SIZE];
> -- 
> 2.5.5