perf record: Fix .tid and .pid fill-in when synthesizing events

Noticed when trying to record events for a firefox thread. We
were synthesizing both .tid and .pid with the pid passed via
--pid.

Fix it by reading /proc/PID/status and getting the tgid
to use in .pid, .tid gets the specified "pid".

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Frédéric Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mike Galbraith <efault@gmx.de>
LKML-Reference: <20090811192200.GF18061@ghostprotocols.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 38 insertions, 33 deletions

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 0345aad8eba..30b83def03d 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -203,46 +203,48 @@ static void sig_atexit(void)
         kill(getpid(), signr);
 }
 
-static void pid_synthesize_comm_event(pid_t pid, int full)
+static pid_t pid_synthesize_comm_event(pid_t pid, int full)
 {
         struct comm_event comm_ev;
         char filename[PATH_MAX];
         char bf[BUFSIZ];
-        int fd;
-        size_t size;
-        char *field, *sep;
+        FILE *fp;
+        size_t size = 0;
         DIR *tasks;
         struct dirent dirent, *next;
+        pid_t tgid = 0;
 
-        snprintf(filename, sizeof(filename), "/proc/%d/stat", pid);
+        snprintf(filename, sizeof(filename), "/proc/%d/status", pid);
 
-        fd = open(filename, O_RDONLY);
-        if (fd < 0) {
+        fp = fopen(filename, "r");
+        if (fd == NULL) {
                 /*
                  * We raced with a task exiting - just return:
                  */
                 if (verbose)
                         fprintf(stderr, "couldn't open %s\n", filename);
-                return;
+                return 0;
         }
-        if (read(fd, bf, sizeof(bf)) < 0) {
-                fprintf(stderr, "couldn't read %s\n", filename);
-                exit(EXIT_FAILURE);
-        }
-        close(fd);
 
-        /* 9027 (cat) R 6747 9027 6747 34816 9027 ... */
         memset(&comm_ev, 0, sizeof(comm_ev));
-        field = strchr(bf, '(');
-        if (field == NULL)
-                goto out_failure;
-        sep = strchr(++field, ')');
-        if (sep == NULL)
-                goto out_failure;
-        size = sep - field;
-        memcpy(comm_ev.comm, field, size++);
-
-        comm_ev.pid = pid;
+        while (!comm_ev.comm[0] || !comm_ev.pid) {
+                if (fgets(bf, sizeof(bf), fp) == NULL)
+                        goto out_failure;
+
+                if (memcmp(bf, "Name:", 5) == 0) {
+                        char *name = bf + 5;
+                        while (*name && isspace(*name))
+                                ++name;
+                        size = strlen(name) - 1;
+                        memcpy(comm_ev.comm, name, size++);
+                } else if (memcmp(bf, "Tgid:", 5) == 0) {
+                        char *tgids = bf + 5;
+                        while (*tgids && isspace(*tgids))
+                                ++tgids;
+                        tgid = comm_ev.pid = atoi(tgids);
+                }
+        }
+
         comm_ev.header.type = PERF_EVENT_COMM;
         size = ALIGN(size, sizeof(u64));
         comm_ev.header.size = sizeof(comm_ev) - (sizeof(comm_ev.comm) - size);
@@ -251,7 +253,7 @@ static void pid_synthesize_comm_event(pid_t pid, int full)
                 comm_ev.tid = pid;
 
                 write_output(&comm_ev, comm_ev.header.size);
-                return;
+                goto out_fclose;
         }
 
         snprintf(filename, sizeof(filename), "/proc/%d/task", pid);
@@ -268,7 +270,10 @@ static void pid_synthesize_comm_event(pid_t pid, int full)
                 write_output(&comm_ev, comm_ev.header.size);
         }
         closedir(tasks);
-        return;
+
+out_fclose:
+        fclose(fp);
+        return tgid;
 
 out_failure:
         fprintf(stderr, "couldn't get COMM and pgid, malformed %s\n",
@@ -276,7 +281,7 @@ out_failure:
         exit(EXIT_FAILURE);
 }
 
-static void pid_synthesize_mmap_samples(pid_t pid)
+static void pid_synthesize_mmap_samples(pid_t pid, pid_t tgid)
 {
         char filename[PATH_MAX];
         FILE *fp;
@@ -328,7 +333,7 @@ static void pid_synthesize_mmap_samples(pid_t pid)
                         mmap_ev.len -= mmap_ev.start;
                         mmap_ev.header.size = (sizeof(mmap_ev) -
                                                (sizeof(mmap_ev.filename) - size));
-                        mmap_ev.pid = pid;
+                        mmap_ev.pid = tgid;
                         mmap_ev.tid = pid;
 
                         write_output(&mmap_ev, mmap_ev.header.size);
@@ -347,14 +352,14 @@ static void synthesize_all(void)
 
         while (!readdir_r(proc, &dirent, &next) && next) {
                 char *end;
-                pid_t pid;
+                pid_t pid, tgid;
 
                 pid = strtol(dirent.d_name, &end, 10);
                 if (*end) /* only interested in proper numerical dirents */
                         continue;
 
-                pid_synthesize_comm_event(pid, 1);
-                pid_synthesize_mmap_samples(pid);
+                tgid = pid_synthesize_comm_event(pid, 1);
+                pid_synthesize_mmap_samples(pid, tgid);
         }
 
         closedir(proc);
@@ -567,8 +572,8 @@ static int __cmd_record(int argc, const char **argv)
                 perf_header__write(header, output);
 
         if (!system_wide) {
-                pid_synthesize_comm_event(pid, 0);
-                pid_synthesize_mmap_samples(pid);
+                pid_t tgid = pid_synthesize_comm_event(pid, 0);
+                pid_synthesize_mmap_samples(pid, tgid);
         } else
                 synthesize_all();