perf tools: Add time out to force stop proc map processing

System wide sampling like 'perf top' or 'perf record -a' read all
threads /proc/xxx/maps before sampling. If there are any threads which
generating a keeping growing huge maps, perf will do infinite loop
during synthesizing. Nothing will be sampled.

This patch fixes this issue by adding per-thread timeout to force stop
this kind of endless proc map processing.

PERF_RECORD_MISC_PROC_MAP_PARSE_TIME_OUT is introduced to indicate that
the mmap record are truncated by time out. User will get warning
notification when truncated mmap records are detected.

Reported-by: Ying Huang <ying.huang@intel.com>
Signed-off-by: Kan Liang <kan.liang@intel.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ying Huang <ying.huang@intel.com>
Link: http://lkml.kernel.org/r/1434549071-25611-1-git-send-email-kan.liang@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

4 files changed, 34 insertions, 0 deletions

diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index 613ed9ad588f..d97f84c080da 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -566,6 +566,10 @@ struct perf_event_mmap_page {
 #define PERF_RECORD_MISC_GUEST_USER             (5 << 0)
 
 /*
+ * Indicates that /proc/PID/maps parsing are truncated by time out.
+ */
+#define PERF_RECORD_MISC_PROC_MAP_PARSE_TIMEOUT (1 << 12)
+/*
  * PERF_RECORD_MISC_MMAP_DATA and PERF_RECORD_MISC_COMM_EXEC are used on
  * different events so can reuse the same bit position.
  */
diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c
index 793b1503d437..416ba80c628f 100644
--- a/tools/perf/util/event.c
+++ b/tools/perf/util/event.c
@@ -213,6 +213,8 @@ static int perf_event__synthesize_fork(struct perf_tool *tool,
         return 0;
 }
 
+#define PROC_MAP_PARSE_TIMEOUT  (500 * 1000000ULL)
+
 int perf_event__synthesize_mmap_events(struct perf_tool *tool,
                                        union perf_event *event,
                                        pid_t pid, pid_t tgid,
@@ -222,6 +224,8 @@ int perf_event__synthesize_mmap_events(struct perf_tool *tool,
 {
         char filename[PATH_MAX];
         FILE *fp;
+        unsigned long long t;
+        bool truncation = false;
         int rc = 0;
 
         if (machine__is_default_guest(machine))
@@ -240,6 +244,7 @@ int perf_event__synthesize_mmap_events(struct perf_tool *tool,
         }
 
         event->header.type = PERF_RECORD_MMAP2;
+        t = rdclock();
 
         while (1) {
                 char bf[BUFSIZ];
@@ -253,6 +258,12 @@ int perf_event__synthesize_mmap_events(struct perf_tool *tool,
                 if (fgets(bf, sizeof(bf), fp) == NULL)
                         break;
 
+                if ((rdclock() - t) > PROC_MAP_PARSE_TIMEOUT) {
+                        pr_warning("Reading %s time out.\n", filename);
+                        truncation = true;
+                        goto out;
+                }
+
                 /* ensure null termination since stack will be reused. */
                 strcpy(execname, "");
 
@@ -301,6 +312,10 @@ int perf_event__synthesize_mmap_events(struct perf_tool *tool,
                         event->header.misc |= PERF_RECORD_MISC_MMAP_DATA;
                 }
 
+out:
+                if (truncation)
+                        event->header.misc |= PERF_RECORD_MISC_PROC_MAP_PARSE_TIMEOUT;
+
                 if (!strcmp(execname, ""))
                         strcpy(execname, anonstr);
 
@@ -319,6 +334,9 @@ int perf_event__synthesize_mmap_events(struct perf_tool *tool,
                         rc = -1;
                         break;
                 }
+
+                if (truncation)
+                        break;
         }
 
         fclose(fp);
diff --git a/tools/perf/util/event.h b/tools/perf/util/event.h
index 5dc51ada05df..39868f529cab 100644
--- a/tools/perf/util/event.h
+++ b/tools/perf/util/event.h
@@ -265,6 +265,7 @@ struct events_stats {
         u32 nr_unknown_id;
         u32 nr_unprocessable_samples;
         u32 nr_auxtrace_errors[PERF_AUXTRACE_ERROR_MAX];
+        u32 nr_proc_map_timeout;
 };
 
 struct attr_event {
diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index c371336d1eb2..2d882fd1f1b9 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -1064,6 +1064,8 @@ static int machines__deliver_event(struct machines *machines,
         case PERF_RECORD_MMAP:
                 return tool->mmap(tool, event, sample, machine);
         case PERF_RECORD_MMAP2:
+                if (event->header.misc & PERF_RECORD_MISC_PROC_MAP_PARSE_TIMEOUT)
+                        ++evlist->stats.nr_proc_map_timeout;
                 return tool->mmap2(tool, event, sample, machine);
         case PERF_RECORD_COMM:
                 return tool->comm(tool, event, sample, machine);
@@ -1360,6 +1362,15 @@ static void perf_session__warn_about_errors(const struct perf_session *session)
                 ui__warning("%u out of order events recorded.\n", oe->nr_unordered_events);
 
         events_stats__auxtrace_error_warn(stats);
+
+        if (stats->nr_proc_map_timeout != 0) {
+                ui__warning("%d map information files for pre-existing threads were\n"
+                            "not processed, if there are samples for addresses they\n"
+                            "will not be resolved, you may find out which are these\n"
+                            "threads by running with -v and redirecting the output\n"
+                            "to a file.\n",
+                            stats->nr_proc_map_timeout);
+        }
 }
 
 static int perf_session__flush_thread_stack(struct thread *thread,