perf tools: Look up thread names for system wide profiling

This handles multithreaded processes with named threads when doing
system wide profiling: the comm for each thread is looked up allowing
them to be different from the thread group leader.

v2:
- fixed sizeof arg to perf_event__get_comm_tgid

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1324578603-12762-3-git-send-email-dsahern@gmail.com
Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 53 insertions, 22 deletions

diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c
index a5787260181a..73ddaf06b8e7 100644
--- a/tools/perf/util/event.c
+++ b/tools/perf/util/event.c
@@ -43,37 +43,27 @@ static struct perf_sample synth_sample = {
         .period    = 1,
 };
 
-static pid_t perf_event__synthesize_comm(struct perf_tool *tool,
-                                         union perf_event *event, pid_t pid,
-                                         int full, perf_event__handler_t process,
-                                         struct machine *machine)
+static pid_t perf_event__get_comm_tgid(pid_t pid, char *comm, size_t len)
 {
         char filename[PATH_MAX];
         char bf[BUFSIZ];
         FILE *fp;
         size_t size = 0;
-        DIR *tasks;
-        struct dirent dirent, *next;
-        pid_t tgid = 0;
+        pid_t tgid = -1;
 
         snprintf(filename, sizeof(filename), "/proc/%d/status", pid);
 
         fp = fopen(filename, "r");
         if (fp == NULL) {
-out_race:
-                /*
-                 * We raced with a task exiting - just return:
-                 */
                 pr_debug("couldn't open %s\n", filename);
                 return 0;
         }
 
-        memset(&event->comm, 0, sizeof(event->comm));
-
-        while (!event->comm.comm[0] || !event->comm.pid) {
+        while (!comm[0] || (tgid < 0)) {
                 if (fgets(bf, sizeof(bf), fp) == NULL) {
-                        pr_warning("couldn't get COMM and pgid, malformed %s\n", filename);
-                        goto out;
+                        pr_warning("couldn't get COMM and pgid, malformed %s\n",
+                                   filename);
+                        break;
                 }
 
                 if (memcmp(bf, "Name:", 5) == 0) {
@@ -81,16 +71,46 @@ out_race:
                         while (*name && isspace(*name))
                                 ++name;
                         size = strlen(name) - 1;
-                        memcpy(event->comm.comm, name, size++);
+                        if (size >= len)
+                                size = len - 1;
+                        memcpy(comm, name, size);
+
                 } else if (memcmp(bf, "Tgid:", 5) == 0) {
                         char *tgids = bf + 5;
                         while (*tgids && isspace(*tgids))
                                 ++tgids;
-                        tgid = event->comm.pid = atoi(tgids);
+                        tgid = atoi(tgids);
                 }
         }
 
+        fclose(fp);
+
+        return tgid;
+}
+
+static pid_t perf_event__synthesize_comm(struct perf_tool *tool,
+                                         union perf_event *event, pid_t pid,
+                                         int full,
+                                         perf_event__handler_t process,
+                                         struct machine *machine)
+{
+        char filename[PATH_MAX];
+        size_t size;
+        DIR *tasks;
+        struct dirent dirent, *next;
+        pid_t tgid;
+
+        memset(&event->comm, 0, sizeof(event->comm));
+
+        tgid = perf_event__get_comm_tgid(pid, event->comm.comm,
+                                         sizeof(event->comm.comm));
+        if (tgid < 0)
+                goto out;
+
+        event->comm.pid = tgid;
         event->comm.header.type = PERF_RECORD_COMM;
+
+        size = strlen(event->comm.comm) + 1;
         size = ALIGN(size, sizeof(u64));
         memset(event->comm.comm + size, 0, machine->id_hdr_size);
         event->comm.header.size = (sizeof(event->comm) -
@@ -106,8 +126,10 @@ out_race:
         snprintf(filename, sizeof(filename), "/proc/%d/task", pid);
 
         tasks = opendir(filename);
-        if (tasks == NULL)
-                goto out_race;
+        if (tasks == NULL) {
+                pr_debug("couldn't open %s\n", filename);
+                return 0;
+        }
 
         while (!readdir_r(tasks, &dirent, &next) && next) {
                 char *end;
@@ -115,6 +137,17 @@ out_race:
                 if (*end)
                         continue;
 
+                /* already have tgid; jut want to update the comm */
+                (void) perf_event__get_comm_tgid(pid, event->comm.comm,
+                                         sizeof(event->comm.comm));
+
+                size = strlen(event->comm.comm) + 1;
+                size = ALIGN(size, sizeof(u64));
+                memset(event->comm.comm + size, 0, machine->id_hdr_size);
+                event->comm.header.size = (sizeof(event->comm) -
+                                          (sizeof(event->comm.comm) - size) +
+                                          machine->id_hdr_size);
+
                 event->comm.tid = pid;
 
                 process(tool, event, &synth_sample, machine);
@@ -122,8 +155,6 @@ out_race:
 
         closedir(tasks);
 out:
-        fclose(fp);
-
         return tgid;
 }