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

From: Don Zickus
Date: Tue Mar 31 2015 - 12:23:18 EST

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@xxxxxxxxxx>

>
> Signed-off-by: David Ahern <dsahern@xxxxxxxxx>
> Cc: Don Zickus <dzickus@xxxxxxxxxx>
> Cc: Joe Mario <jmario@xxxxxxxxxx>
> Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
> ---
> 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
>
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