Date:   Mon,  6 Mar 2017 18:43:00 +0530
From:   Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com>
To:     mingo@...hat.com, acme@...nel.org, mhiramat@...nel.org
Cc:     brendan.d.gregg@...il.com, peterz@...radead.org,
        alexander.shishkin@...ux.intel.com, wangnan0@...wei.com,
        jolsa@...nel.org, ak@...ux.intel.com, treeze.taeung@...il.com,
        mathieu.poirier@...aro.org, hekuang@...wei.com,
        sukadev@...ux.vnet.ibm.com, ananth@...ibm.com,
        naveen.n.rao@...ux.vnet.ibm.com, adrian.hunter@...el.com,
        linux-kernel@...r.kernel.org, hemant@...ux.vnet.ibm.com,
        Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com>
Subject: [PATCH v4 3/7] perf/sdt: Allow recording of existing events

Add functionality to fetch matching events from uprobe_events. If no
events are fourd from it, fetch matching events from probe-cache and
add them in uprobe_events. If all events are already present in
uprobe_events, reuse them. If few of them are present, add entries
for missing events and record them. At the end of the record session,
delete newly added entries. Below is detailed algorithm that describe
implementation of this patch:

    arr1 = fetch all sdt events from uprobe_events

    if (event with exact name in arr1)
        add that in sdt_event_list
        return

    if (user has used pattern)
        if (pattern matching entries found from arr1)
            add those events in sdt_event_list
            return

    arr2 = lookup probe-cache
    if (arr2 empty)
        return

    ctr = 0
    foreach (compare entries of arr1 and arr2 using filepath+address)
        if (match)
            add event from arr1 to sdt_event_list
            ctr++
            if (!pattern used)
                remove entry from arr2

    if (!pattern used || ctr == 0)
        add all entries of arr2 in sdt_event_list


Example: Consider sdt event sdt_libpthread:mutex_release found in
/usr/lib64/libpthread-2.24.so.

  $ readelf -n /usr/lib64/libpthread-2.24.so | grep -A2 Provider
      Provider: libpthread
      Name: mutex_release
      Location: 0x000000000000b126, Base: 0x00000000000139cc, Semaphore: 0x0000000000000000
    --
      Provider: libpthread
      Name: mutex_release
      Location: 0x000000000000b2f6, Base: 0x00000000000139cc, Semaphore: 0x0000000000000000
    --
      Provider: libpthread
      Name: mutex_release
      Location: 0x000000000000b498, Base: 0x00000000000139cc, Semaphore: 0x0000000000000000
    --
      Provider: libpthread
      Name: mutex_release
      Location: 0x000000000000b596, Base: 0x00000000000139cc, Semaphore: 0x0000000000000000

When no probepoint exists,

  $ sudo ./perf record -a -e sdt_libpthread:mutex_*
    Warning: Recording on 15 occurrences of sdt_libpthread:mutex_*

  $ sudo ./perf record -a -e sdt_libpthread:mutex_release
    Warning: Recording on 4 occurrences of sdt_libpthread:mutex_release
  $ sudo ./perf evlist
    sdt_libpthread:mutex_release_3
    sdt_libpthread:mutex_release_2
    sdt_libpthread:mutex_release_1
    sdt_libpthread:mutex_release

When probepoints already exists for all matching events,

  $ sudo ./perf probe sdt_libpthread:mutex_release
    Added new events:
      sdt_libpthread:mutex_release (on %mutex_release in /usr/lib64/libpthread-2.24.so)
      sdt_libpthread:mutex_release_1 (on %mutex_release in /usr/lib64/libpthread-2.24.so)
      sdt_libpthread:mutex_release_2 (on %mutex_release in /usr/lib64/libpthread-2.24.so)
      sdt_libpthread:mutex_release_3 (on %mutex_release in /usr/lib64/libpthread-2.24.so)

  $ sudo ./perf record -a -e sdt_libpthread:mutex_release_1
  $ sudo ./perf evlist
    sdt_libpthread:mutex_release_1

  $ sudo ./perf record -a -e sdt_libpthread:mutex_release
  $ sudo ./perf evlist
    sdt_libpthread:mutex_release

  $ sudo ./perf record -a -e sdt_libpthread:mutex_*
    Warning: Recording on 4 occurrences of sdt_libpthread:mutex_*
  $ sudo ./perf evlist
    sdt_libpthread:mutex_release_3
    sdt_libpthread:mutex_release_2
    sdt_libpthread:mutex_release_1
    sdt_libpthread:mutex_release

  $ sudo ./perf record -a -e sdt_libpthread:mutex_release_*
    Warning: Recording on 3 occurrences of sdt_libpthread:mutex_release_*

When probepoints are partially exists,

  $ sudo ./perf probe -d sdt_libpthread:mutex_release
  $ sudo ./perf probe -d sdt_libpthread:mutex_release_2

  $ sudo ./perf record -a -e sdt_libpthread:mutex_release
    Warning: Recording on 4 occurrences of sdt_libpthread:mutex_release
  $ sudo ./perf evlist
    sdt_libpthread:mutex_release
    sdt_libpthread:mutex_release_3
    sdt_libpthread:mutex_release_2
    sdt_libpthread:mutex_release_1

  $ sudo ./perf record -a -e sdt_libpthread:mutex_release*
    Warning: Recording on 2 occurrences of sdt_libpthread:mutex_release*
  $ sudo ./perf evlist
    sdt_libpthread:mutex_release_3
    sdt_libpthread:mutex_release_1

  $ sudo ./perf record -a -e sdt_libpthread:*
    Warning: Recording on 2 occurrences of sdt_libpthread:*
  $ sudo ./perf evlist
    sdt_libpthread:mutex_release_3
    sdt_libpthread:mutex_release_1

Signed-off-by: Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com>
---
 tools/perf/util/probe-event.c |  58 +++++++++++++-
 tools/perf/util/probe-event.h |   5 ++
 tools/perf/util/probe-file.c  | 173 +++++++++++++++++++++++++++++++++++++-----
 tools/perf/util/probe-file.h  |   3 +-
 4 files changed, 215 insertions(+), 24 deletions(-)

diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index b879076..947b2ec 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -231,7 +231,7 @@ static void clear_perf_probe_point(struct perf_probe_point *pp)
 	free(pp->lazy_line);
 }
 
-static void clear_probe_trace_events(struct probe_trace_event *tevs, int ntevs)
+void clear_probe_trace_events(struct probe_trace_event *tevs, int ntevs)
 {
 	int i;
 
@@ -1198,7 +1198,7 @@ static int parse_line_num(char **ptr, int *val, const char *what)
 }
 
 /* Check the name is good for event, group or function */
-static bool is_c_func_name(const char *name)
+bool is_c_func_name(const char *name)
 {
 	if (!isalpha(*name) && *name != '_')
 		return false;
@@ -3491,6 +3491,9 @@ void remove_sdt_event_list(struct list_head *sdt_events)
 		return;
 
 	list_for_each_entry(sdt_event, sdt_events, list) {
+		if (sdt_event->exst)
+			continue;
+
 		if (!filter) {
 			filter = strfilter__new(sdt_event->name, &err);
 			if (!filter)
@@ -3500,8 +3503,57 @@ void remove_sdt_event_list(struct list_head *sdt_events)
 		}
 	}
 
-	del_perf_probe_events(filter);
+	if (filter)
+		del_perf_probe_events(filter);
 
 free_list:
 	free_sdt_list(sdt_events);
 }
+
+/*
+ * Look into uprobe_events file and prepare list of sdt events
+ * whose probepoint is already registered.
+ */
+int get_exist_sdt_events(struct probe_trace_event **tevs)
+{
+	int fd, ret, ntevs = 0;
+	struct strlist *rawlist;
+	struct str_node *ent;
+	struct probe_trace_event *tev;
+
+	fd = probe_file__open(PF_FL_RW | PF_FL_UPROBE);
+	if (fd < 0)
+		return fd;
+
+	rawlist = probe_file__get_rawlist(fd);
+	strlist__for_each_entry(ent, rawlist) {
+		tev = zalloc(sizeof(struct probe_trace_event));
+		if (!tev) {
+			ret = -ENOMEM;
+			goto err;
+		}
+
+		ret = parse_probe_trace_command(ent->s, tev);
+		if (ret < 0)
+			goto err;
+
+		if (strncmp(tev->group, "sdt_", 4)) {
+			/* Interested in SDT events only. */
+			free(tev);
+			continue;
+		}
+
+		ret = concat_probe_trace_events(tevs, &ntevs, &tev, 1);
+		if (ret < 0)
+			goto err;
+	}
+
+	close(fd);
+	return ntevs;
+
+err:
+	close(fd);
+	clear_probe_trace_events(*tevs, ntevs);
+	zfree(tevs);
+	return ret;
+}
diff --git a/tools/perf/util/probe-event.h b/tools/perf/util/probe-event.h
index 91e277e..dc89eb5 100644
--- a/tools/perf/util/probe-event.h
+++ b/tools/perf/util/probe-event.h
@@ -138,6 +138,9 @@ bool perf_probe_event_need_dwarf(struct perf_probe_event *pev);
 /* Release event contents */
 void clear_perf_probe_event(struct perf_probe_event *pev);
 void clear_probe_trace_event(struct probe_trace_event *tev);
+void clear_probe_trace_events(struct probe_trace_event *tevs, int ntevs);
+
+bool is_c_func_name(const char *name);
 
 /* Command string to line-range */
 int parse_line_range_desc(const char *cmd, struct line_range *lr);
@@ -186,4 +189,6 @@ int parse_perf_probe_event_name(char **arg, struct perf_probe_event *pev);
 
 int find_cached_events_all(struct perf_probe_event *pev,
 			   struct probe_trace_event **tevs);
+
+int get_exist_sdt_events(struct probe_trace_event **tevs);
 #endif /*_PROBE_EVENT_H */
diff --git a/tools/perf/util/probe-file.c b/tools/perf/util/probe-file.c
index c1cf67f..47b624a 100644
--- a/tools/perf/util/probe-file.c
+++ b/tools/perf/util/probe-file.c
@@ -964,16 +964,14 @@ static int get_sdt_events_from_cache(struct perf_probe_event *pev)
 		pr_err("Error: %s:%s not found in the cache\n",
 			pev->group, pev->event);
 		ret = -EINVAL;
-	} else if (pev->ntevs > 1) {
-		pr_warning("Warning : Recording on %d occurences of %s:%s\n",
-			   pev->ntevs, pev->group, pev->event);
 	}
 
 	return ret;
 }
 
 static int add_event_to_sdt_evlist(struct probe_trace_event *tev,
-				   struct list_head *sdt_evlist)
+				   struct list_head *sdt_evlist,
+				   bool exst)
 {
 	struct sdt_event_list *tmp;
 
@@ -988,6 +986,7 @@ static int add_event_to_sdt_evlist(struct probe_trace_event *tev,
 
 	snprintf(tmp->name, strlen(tev->group) + strlen(tev->event) + 2,
 		 "%s:%s", tev->group, tev->event);
+	tmp->exst = exst;
 	list_add(&tmp->list, sdt_evlist);
 
 	return 0;
@@ -999,7 +998,7 @@ static int add_events_to_sdt_evlist(struct perf_probe_event *pev,
 	int i, ret;
 
 	for (i = 0; i < pev->ntevs; i++) {
-		ret = add_event_to_sdt_evlist(&pev->tevs[i], sdt_evlist);
+		ret = add_event_to_sdt_evlist(&pev->tevs[i], sdt_evlist, false);
 
 		if (ret < 0)
 			return ret;
@@ -1007,14 +1006,133 @@ static int add_events_to_sdt_evlist(struct perf_probe_event *pev,
 	return 0;
 }
 
-/*
- * Find the SDT event from the cache and if found add it/them
- * to the uprobe_events file
- */
+static bool sdt_is_ptrn_used(struct perf_probe_event *pev)
+{
+	return !is_c_func_name(pev->group) || !is_c_func_name(pev->event);
+}
+
+static bool sdt_name_match(struct perf_probe_event *pev,
+			   struct probe_trace_event *tev)
+{
+	if (sdt_is_ptrn_used(pev))
+		return strglobmatch(tev->group, pev->group) &&
+			strglobmatch(tev->event, pev->event);
+
+	return !strcmp(tev->group, pev->group) &&
+		!strcmp(tev->event, pev->event);
+}
+
+static void sdt_warn_multi_events(int ctr, struct perf_probe_event *pev)
+{
+	pr_warning("Warning: Recording on %d occurrences of %s:%s\n",
+		   ctr, pev->group, pev->event);
+}
+
+static int sdt_event_probepoint_exists(struct perf_probe_event *pev,
+				       struct probe_trace_event *tevs,
+				       int ntevs,
+				       struct list_head *sdt_evlist)
+{
+	int i = 0, ret = 0, ctr = 0;
+
+	for (i = 0; i < ntevs; i++) {
+		if (sdt_name_match(pev, &tevs[i])) {
+			ret = add_event_to_sdt_evlist(&tevs[i],
+						sdt_evlist, true);
+			if (ret < 0)
+				return ret;
+
+			ctr++;
+		}
+	}
+
+	if (ctr > 1)
+		sdt_warn_multi_events(ctr, pev);
+
+	return ctr;
+}
+
+static bool sdt_file_addr_match(struct probe_trace_event *tev1,
+				struct probe_trace_event *tev2)
+{
+	return (tev1->point.address == tev2->point.address &&
+		!(strcmp(tev1->point.module, tev2->point.module)));
+}
+
+static void shift_sdt_events(struct perf_probe_event *pev, int i)
+{
+	int j = 0;
+
+	clear_probe_trace_event(&pev->tevs[i]);
+
+	if (i == pev->ntevs - 1)
+		goto out;
+
+	for (j = i; j < pev->ntevs - 1; j++)
+		memcpy(&pev->tevs[j], &pev->tevs[j + 1],
+		       sizeof(struct probe_trace_event));
+
+out:
+	pev->ntevs--;
+}
+
+static int sdt_merge_events(struct perf_probe_event *pev,
+			    struct probe_trace_event *exst_tevs,
+			    int exst_ntevs,
+			    struct list_head *sdt_evlist)
+{
+	int i, j, ret = 0, ctr = 0;
+	bool ptrn_used = sdt_is_ptrn_used(pev);
+
+	for (i = 0; i < pev->ntevs; i++) {
+		for (j = 0; j < exst_ntevs; j++) {
+			if (sdt_file_addr_match(&pev->tevs[i],
+						&exst_tevs[j])) {
+				ret = add_event_to_sdt_evlist(&exst_tevs[j],
+							  sdt_evlist, true);
+				if (ret < 0)
+					return ret;
+
+				if (!ptrn_used)
+					shift_sdt_events(pev, i);
+				ctr++;
+			}
+		}
+	}
+
+	if (!ptrn_used || ctr == 0) {
+		/*
+		 * Create probe point for all probe-cached events by
+		 * adding them in uprobe_events file.
+		 */
+		ret = apply_perf_probe_events(pev, 1);
+		if (ret < 0) {
+			pr_err("Error in adding SDT event: %s:%s\n",
+				pev->group, pev->event);
+			goto out;
+		}
+
+		/* Add events to sdt_evlist. */
+		ret = add_events_to_sdt_evlist(pev, sdt_evlist);
+		if (ret < 0) {
+			pr_err("Error while updating event list\n");
+			goto out;
+		}
+
+		ctr += pev->ntevs;
+		if (ctr > 1)
+			sdt_warn_multi_events(ctr, pev);
+	}
+
+out:
+	return ret;
+}
+
 int add_sdt_event(char *event, struct list_head *sdt_evlist)
 {
 	struct perf_probe_event *pev;
-	int ret;
+	int ret, exst_ntevs;
+	struct probe_trace_event *exst_tevs = NULL;
 
 	pev = zalloc(sizeof(*pev));
 	if (!pev)
@@ -1037,23 +1155,37 @@ int add_sdt_event(char *event, struct list_head *sdt_evlist)
 	probe_conf.max_probes = MAX_PROBES;
 	probe_conf.force_add = 1;
 
+	/* Fetch all sdt events from uprobe_events */
+	exst_ntevs = get_exist_sdt_events(&exst_tevs);
+	if (exst_ntevs < 0) {
+		ret = exst_ntevs;
+		goto free_pev;
+	}
+
+	/* Check if events with same name already exists in uprobe_events. */
+	ret = sdt_event_probepoint_exists(pev, exst_tevs,
+					 exst_ntevs, sdt_evlist);
+	if (ret) {
+		ret = ret > 0 ? 0 : ret;
+		goto free_pev;
+	}
+
 	/* Fetch all matching events from cache. */
 	ret = get_sdt_events_from_cache(pev);
 	if (ret < 0)
 		goto free_pev;
 
 	/*
-	 * Create probe point for all events by adding them in
-	 * uprobe_events file
+	 * Merge events found from uprobe_events with events found
+	 * from cache. Reuse events whose probepoint already exists
+	 * in uprobe_events, while add new entries for other events
+	 * in uprobe_events.
+	 *
+	 * This always tries to give first priority to events from
+	 * uprobe_events. By doing so, it ensures the existing
+	 * behaviour of perf remains same for sdt events too.
 	 */
-	ret = apply_perf_probe_events(pev, 1);
-	if (ret) {
-		pr_err("Error in adding SDT event : %s\n", event);
-		goto free_pev;
-	}
-
-	/* Add events to sdt_evlist */
-	ret = add_events_to_sdt_evlist(pev, sdt_evlist);
+	ret = sdt_merge_events(pev, exst_tevs, exst_ntevs, sdt_evlist);
 	if (ret < 0)
 		goto free_pev;
 
@@ -1063,6 +1195,7 @@ int add_sdt_event(char *event, struct list_head *sdt_evlist)
 	if (ret < 0)
 		free_sdt_list(sdt_evlist);
 	cleanup_perf_probe_events(pev, 1);
+	clear_probe_trace_events(exst_tevs, exst_ntevs);
 	free(pev);
 	return ret;
 }
diff --git a/tools/perf/util/probe-file.h b/tools/perf/util/probe-file.h
index 6d2d3e5..7126adf 100644
--- a/tools/perf/util/probe-file.h
+++ b/tools/perf/util/probe-file.h
@@ -20,8 +20,9 @@ struct probe_cache {
 };
 
 struct sdt_event_list {
-	char *name;		/* group:event */
 	struct list_head list;
+	char *name;             /* group:event */
+	bool exst;              /* Even already exists in uprobe_events? */
 };
 
 enum probe_type {
-- 
2.9.3

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