work correctly without CONFIG_SCHED_DEBUG (#10)

The app appeared to work without CONFIG_SCHED_DEBUG (no error messages),
but the PS part of the graph was not plotted, and process command lines
were not collected with -C. It was hard to find out what's the reason. A
small change fixes the code to work correctly without requirement for
this config.

README

@@ -1,3 +1,4 @@
 For systemd-bootchart, several proc debug interfaces are required in the kernel config:
   CONFIG_SCHEDSTATS
+below is optional, for additional info:
   CONFIG_SCHED_DEBUG

src/store.c

@@ -252,48 +252,49 @@ int log_sample(DIR *proc,
                         ps->sample->runtime = atoll(rt);
                         ps->sample->waittime = atoll(wt);
 
-                        /* get name, start time */
+                        /* get name, start time; requires CONFIG_SCHED_DEBUG in kernel */
                         if (ps->sched < 0) {
                                 sprintf(filename, "%d/sched", pid);
                                 ps->sched = openat(procfd, filename, O_RDONLY|O_CLOEXEC);
                                 if (ps->sched < 0)
-                                        continue;
+                                        goto no_sched;
                         }
 
                         s = pread(ps->sched, buf, sizeof(buf) - 1, 0);
                         if (s <= 0) {
                                 ps->sched = safe_close(ps->sched);
-                                continue;
+                                goto no_sched;
                         }
                         buf[s] = '\0';
 
                         if (!sscanf(buf, "%s %*s %*s", key))
-                                continue;
+                                goto no_sched;
 
                         strscpy(ps->name, sizeof(ps->name), key);
 
-                        /* cmdline */
-                        if (arg_show_cmdline)
-                                pid_cmdline_strscpy(procfd, ps->name, sizeof(ps->name), pid);
-
                         /* discard line 2 */
                         m = bufgetline(buf);
                         if (!m)
-                                continue;
+                                goto no_sched;
 
                         m = bufgetline(m);
                         if (!m)
-                                continue;
+                                goto no_sched;
 
                         if (!sscanf(m, "%*s %*s %s", t))
-                                continue;
+                                goto no_sched;
 
                         r = safe_atod(t, &ps->starttime);
                         if (r < 0)
-                                continue;
+                                goto no_sched;
 
                         ps->starttime /= 1000.0;
 
+no_sched:
+                        /* cmdline */
+                        if (arg_show_cmdline)
+                                pid_cmdline_strscpy(procfd, ps->name, sizeof(ps->name), pid);
+
                         if (arg_show_cgroup)
                                 /* if this fails, that's OK */
                                 cg_pid_get_path(SYSTEMD_CGROUP_CONTROLLER,
@@ -527,24 +528,25 @@ int log_sample(DIR *proc,
                                 sprintf(filename, "%d/sched", pid);
                                 ps->sched = openat(procfd, filename, O_RDONLY|O_CLOEXEC);
                                 if (ps->sched < 0)
-                                        continue;
+                                        goto no_sched2;
                         }
 
                         s = pread(ps->sched, buf, sizeof(buf) - 1, 0);
                         if (s <= 0) {
                                 /* clean up file descriptors */
                                 ps->sched = safe_close(ps->sched);
                                 ps->schedstat = safe_close(ps->schedstat);
-                                continue;
+                                goto no_sched2;
                         }
 
                         buf[s] = '\0';
 
                         if (!sscanf(buf, "%s %*s %*s", key))
-                                continue;
+                                goto no_sched2;
 
                         strscpy(ps->name, sizeof(ps->name), key);
 
+no_sched2:
                         /* cmdline */
                         if (arg_show_cmdline)
                                 pid_cmdline_strscpy(procfd, ps->name, sizeof(ps->name), pid);