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Subject[PATCH 2/2] perf tool: Fix ppid for synthesized fork events
Date
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.

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>
---
tools/perf/util/event.c | 106 ++++++++++++++++++++++++++++--------------------
1 file changed, 63 insertions(+), 43 deletions(-)

diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c
index b49bee8a283d..648744a21410 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:") */
@@ -109,32 +113,51 @@ static pid_t perf_event__get_comm_tgid(pid_t pid, char *comm, size_t len)
if (nl)
*nl = '\0';

- 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:") */
+
+ while (*ppids && isspace(*ppids))
+ ++ppids;
+
+ nl = strchr(ppids, '\n');
+ if (nl)
+ *nl = '\0';
+
+ *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;
@@ -144,36 +167,35 @@ 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,
- union perf_event *event, pid_t pid,
- perf_event__handler_t process,
- struct machine *machine)
+static int perf_event__synthesize_comm(struct perf_tool *tool,
+ union perf_event *event, pid_t pid,
+ perf_event__handler_t process,
+ struct machine *machine,
+ pid_t *tgid, pid_t *ppid)
{
- pid_t tgid = perf_event__prepare_comm(event, pid, machine);
-
- 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;
+ return 0;
}

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;
@@ -365,14 +387,12 @@ 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) {
- tgid = perf_event__synthesize_comm(tool, comm_event, pid,
- process, machine);
-
- if (tgid == -1)
+ if (perf_event__synthesize_comm(tool, comm_event, pid,
+ process, machine, &tgid, &ppid) != 0)
return -1;

return perf_event__synthesize_mmap_events(tool, mmap_event, pid, tgid,
@@ -400,12 +420,12 @@ 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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