Re: [PATCH v3 2/2] perf tool: Fix ppid for synthesized fork events

[Don Zickus <dzickus@redhat.com>]

On Mon, Mar 30, 2015 at 02:35:58PM -0600, David Ahern wrote:
> 363b785f38 added synthesized fork events and set a thread's parent id
> to itself. Since we are already processing /proc/<pid>/status the ppid
> can be determined properly. Make it so.

Acked-by: Don Zickus <dzickus@redhat.com>

> 
> Signed-off-by: David Ahern <dsahern@gmail.com>
> Cc: Don Zickus <dzickus@redhat.com>
> Cc: Joe Mario <jmario@redhat.com>
> Cc: Jiri Olsa <jolsa@redhat.com>
> ---
> v3
> - removed isspace and newline checks; added brackets per Arnaldo's comments
> 
> v2:
> - removed changes to function signature for perf_event__synthesize_comm as
>   noted by Jiri
> 
>  tools/perf/util/event.c | 83 +++++++++++++++++++++++++++++--------------------
>  1 file changed, 50 insertions(+), 33 deletions(-)
> 
> diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c
> index 023dd3548a94..5516236df6ab 100644
> --- a/tools/perf/util/event.c
> +++ b/tools/perf/util/event.c
> @@ -51,29 +51,32 @@ static struct perf_sample synth_sample = {
>  
>  /*
>   * Assumes that the first 4095 bytes of /proc/pid/stat contains
> - * the comm and tgid.
> + * the comm, tgid and ppid.
>   */
> -static pid_t perf_event__get_comm_tgid(pid_t pid, char *comm, size_t len)
> +static int perf_event__get_comm_ids(pid_t pid, char *comm, size_t len,
> +				    pid_t *tgid, pid_t *ppid)
>  {
>  	char filename[PATH_MAX];
>  	char bf[4096];
>  	int fd;
>  	size_t size = 0, n;
> -	pid_t tgid = -1;
> -	char *nl, *name, *tgids;
> +	char *nl, *name, *tgids, *ppids;
> +
> +	*tgid = -1;
> +	*ppid = -1;
>  
>  	snprintf(filename, sizeof(filename), "/proc/%d/status", pid);
>  
>  	fd = open(filename, O_RDONLY);
>  	if (fd < 0) {
>  		pr_debug("couldn't open %s\n", filename);
> -		return 0;
> +		return -1;
>  	}
>  
>  	n = read(fd, bf, sizeof(bf) - 1);
>  	close(fd);
>  	if (n <= 0) {
> -		pr_warning("Couldn't get COMM and tgid for pid %d\n",
> +		pr_warning("Couldn't get COMM, tigd and ppid for pid %d\n",
>  			   pid);
>  		return -1;
>  	}
> @@ -81,6 +84,7 @@ static pid_t perf_event__get_comm_tgid(pid_t pid, char *comm, size_t len)
>  
>  	name = strstr(bf, "Name:");
>  	tgids = strstr(bf, "Tgid:");
> +	ppids = strstr(bf, "PPid:");
>  
>  	if (name) {
>  		name += 5;  /* strlen("Name:") */
> @@ -103,32 +107,45 @@ static pid_t perf_event__get_comm_tgid(pid_t pid, char *comm, size_t len)
>  
>  	if (tgids) {
>  		tgids += 5;  /* strlen("Tgid:") */
> -		tgid = atoi(tgids);
> +		*tgid = atoi(tgids);
>  	} else {
>  		pr_debug("Tgid: string not found for pid %d\n", pid);
>  	}
>  
> -	return tgid;
> +	if (ppids) {
> +		ppids += 5;  /* strlen("PPid:") */
> +		*ppid = atoi(ppids);
> +	} else {
> +		pr_debug("PPid: string not found for pid %d\n", pid);
> +	}
> +
> +	return 0;
>  }
>  
> -static pid_t perf_event__prepare_comm(union perf_event *event, pid_t pid,
> -					 struct machine *machine)
> +static int perf_event__prepare_comm(union perf_event *event, pid_t pid,
> +				    struct machine *machine,
> +				    pid_t *tgid, pid_t *ppid)
>  {
>  	size_t size;
> -	pid_t tgid;
> +
> +	*ppid = -1;
>  
>  	memset(&event->comm, 0, sizeof(event->comm));
>  
> -	if (machine__is_host(machine))
> -		tgid = perf_event__get_comm_tgid(pid, event->comm.comm,
> -						 sizeof(event->comm.comm));
> -	else
> -		tgid = machine->pid;
> +	if (machine__is_host(machine)) {
> +		if (perf_event__get_comm_ids(pid, event->comm.comm,
> +					     sizeof(event->comm.comm),
> +					     tgid, ppid) != 0) {
> +			return -1;
> +		}
> +	} else {
> +		*tgid = machine->pid;
> +	}
>  
> -	if (tgid < 0)
> -		goto out;
> +	if (*tgid < 0)
> +		return -1;
>  
> -	event->comm.pid = tgid;
> +	event->comm.pid = *tgid;
>  	event->comm.header.type = PERF_RECORD_COMM;
>  
>  	size = strlen(event->comm.comm) + 1;
> @@ -138,8 +155,8 @@ static pid_t perf_event__prepare_comm(union perf_event *event, pid_t pid,
>  				(sizeof(event->comm.comm) - size) +
>  				machine->id_hdr_size);
>  	event->comm.tid = pid;
> -out:
> -	return tgid;
> +
> +	return 0;
>  }
>  
>  static pid_t perf_event__synthesize_comm(struct perf_tool *tool,
> @@ -147,27 +164,27 @@ static pid_t perf_event__synthesize_comm(struct perf_tool *tool,
>  					 perf_event__handler_t process,
>  					 struct machine *machine)
>  {
> -	pid_t tgid = perf_event__prepare_comm(event, pid, machine);
> +	pid_t tgid, ppid;
>  
> -	if (tgid == -1)
> -		goto out;
> +	if (perf_event__prepare_comm(event, pid, machine, &tgid, &ppid) != 0)
> +		return -1;
>  
>  	if (process(tool, event, &synth_sample, machine) != 0)
>  		return -1;
>  
> -out:
>  	return tgid;
>  }
>  
>  static int perf_event__synthesize_fork(struct perf_tool *tool,
> -				       union perf_event *event, pid_t pid,
> -				       pid_t tgid, perf_event__handler_t process,
> +				       union perf_event *event,
> +				       pid_t pid, pid_t tgid, pid_t ppid,
> +				       perf_event__handler_t process,
>  				       struct machine *machine)
>  {
>  	memset(&event->fork, 0, sizeof(event->fork) + machine->id_hdr_size);
>  
> -	event->fork.ppid = tgid;
> -	event->fork.ptid = tgid;
> +	event->fork.ppid = ppid;
> +	event->fork.ptid = ppid;
>  	event->fork.pid  = tgid;
>  	event->fork.tid  = pid;
>  	event->fork.header.type = PERF_RECORD_FORK;
> @@ -359,7 +376,7 @@ static int __event__synthesize_thread(union perf_event *comm_event,
>  	char filename[PATH_MAX];
>  	DIR *tasks;
>  	struct dirent dirent, *next;
> -	pid_t tgid;
> +	pid_t tgid, ppid;
>  
>  	/* special case: only send one comm event using passed in pid */
>  	if (!full) {
> @@ -394,12 +411,12 @@ static int __event__synthesize_thread(union perf_event *comm_event,
>  		if (*end)
>  			continue;
>  
> -		tgid = perf_event__prepare_comm(comm_event, _pid, machine);
> -		if (tgid == -1)
> +		if (perf_event__prepare_comm(comm_event, _pid, machine,
> +					     &tgid, &ppid) != 0)
>  			return -1;
>  
>  		if (perf_event__synthesize_fork(tool, fork_event, _pid, tgid,
> -						process, machine) < 0)
> +						ppid, process, machine) < 0)
>  			return -1;
>  		/*
>  		 * Send the prepared comm event
> -- 
> 2.2.1
>