1 files changed, 404 insertions, 148 deletions

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index 86a03836a83f..097b3ed77fdd 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -15,6 +15,7 @@
 #include "evlist.h"
 #include "evsel.h"
 #include "debug.h"
+#include "asm/bug.h"
 #include <unistd.h>
 
 #include "parse-events.h"
@@ -27,8 +28,8 @@
 #include <linux/log2.h>
 #include <linux/err.h>
 
-static void perf_evlist__mmap_put(struct perf_evlist *evlist, int idx);
-static void __perf_evlist__munmap(struct perf_evlist *evlist, int idx);
+static void perf_mmap__munmap(struct perf_mmap *map);
+static void perf_mmap__put(struct perf_mmap *map);
 
 #define FD(e, x, y) (*(int *)xyarray__entry(e->fd, x, y))
 #define SID(e, x, y) xyarray__entry(e->sample_id, x, y)
@@ -44,6 +45,7 @@ void perf_evlist__init(struct perf_evlist *evlist, struct cpu_map *cpus,
 	perf_evlist__set_maps(evlist, cpus, threads);
 	fdarray__init(&evlist->pollfd, 64);
 	evlist->workload.pid = -1;
+	evlist->bkw_mmap_state = BKW_MMAP_NOTREADY;
 }
 
 struct perf_evlist *perf_evlist__new(void)
@@ -99,7 +101,7 @@ static void perf_evlist__update_id_pos(struct perf_evlist *evlist)
 {
 	struct perf_evsel *evsel;
 
-	evlist__for_each(evlist, evsel)
+	evlist__for_each_entry(evlist, evsel)
 		perf_evsel__calc_id_pos(evsel);
 
 	perf_evlist__set_id_pos(evlist);
@@ -109,7 +111,7 @@ static void perf_evlist__purge(struct perf_evlist *evlist)
 {
 	struct perf_evsel *pos, *n;
 
-	evlist__for_each_safe(evlist, n, pos) {
+	evlist__for_each_entry_safe(evlist, n, pos) {
 		list_del_init(&pos->node);
 		pos->evlist = NULL;
 		perf_evsel__delete(pos);
@@ -121,11 +123,15 @@ static void perf_evlist__purge(struct perf_evlist *evlist)
 void perf_evlist__exit(struct perf_evlist *evlist)
 {
 	zfree(&evlist->mmap);
+	zfree(&evlist->backward_mmap);
 	fdarray__exit(&evlist->pollfd);
 }
 
 void perf_evlist__delete(struct perf_evlist *evlist)
 {
+	if (evlist == NULL)
+		return;
+
 	perf_evlist__munmap(evlist);
 	perf_evlist__close(evlist);
 	cpu_map__put(evlist->cpus);
@@ -160,7 +166,7 @@ static void perf_evlist__propagate_maps(struct perf_evlist *evlist)
 {
 	struct perf_evsel *evsel;
 
-	evlist__for_each(evlist, evsel)
+	evlist__for_each_entry(evlist, evsel)
 		__perf_evlist__propagate_maps(evlist, evsel);
 }
 
@@ -189,7 +195,7 @@ void perf_evlist__splice_list_tail(struct perf_evlist *evlist,
 {
 	struct perf_evsel *evsel, *temp;
 
-	__evlist__for_each_safe(list, temp, evsel) {
+	__evlist__for_each_entry_safe(list, temp, evsel) {
 		list_del_init(&evsel->node);
 		perf_evlist__add(evlist, evsel);
 	}
@@ -204,7 +210,7 @@ void __perf_evlist__set_leader(struct list_head *list)
 
 	leader->nr_members = evsel->idx - leader->idx + 1;
 
-	__evlist__for_each(list, evsel) {
+	__evlist__for_each_entry(list, evsel) {
 		evsel->leader = leader;
 	}
 }
@@ -233,31 +239,13 @@ void perf_event_attr__set_max_precise_ip(struct perf_event_attr *attr)
 
 int perf_evlist__add_default(struct perf_evlist *evlist)
 {
-	struct perf_event_attr attr = {
-		.type = PERF_TYPE_HARDWARE,
-		.config = PERF_COUNT_HW_CPU_CYCLES,
-	};
-	struct perf_evsel *evsel;
-
-	event_attr_init(&attr);
+	struct perf_evsel *evsel = perf_evsel__new_cycles();
 
-	perf_event_attr__set_max_precise_ip(&attr);
-
-	evsel = perf_evsel__new(&attr);
 	if (evsel == NULL)
-		goto error;
-
-	/* use asprintf() because free(evsel) assumes name is allocated */
-	if (asprintf(&evsel->name, "cycles%.*s",
-		     attr.precise_ip ? attr.precise_ip + 1 : 0, ":ppp") < 0)
-		goto error_free;
+		return -ENOMEM;
 
 	perf_evlist__add(evlist, evsel);
 	return 0;
-error_free:
-	perf_evsel__delete(evsel);
-error:
-	return -ENOMEM;
 }
 
 int perf_evlist__add_dummy(struct perf_evlist *evlist)
@@ -295,7 +283,7 @@ static int perf_evlist__add_attrs(struct perf_evlist *evlist,
 	return 0;
 
 out_delete_partial_list:
-	__evlist__for_each_safe(&head, n, evsel)
+	__evlist__for_each_entry_safe(&head, n, evsel)
 		perf_evsel__delete(evsel);
 	return -1;
 }
@@ -316,7 +304,7 @@ perf_evlist__find_tracepoint_by_id(struct perf_evlist *evlist, int id)
 {
 	struct perf_evsel *evsel;
 
-	evlist__for_each(evlist, evsel) {
+	evlist__for_each_entry(evlist, evsel) {
 		if (evsel->attr.type   == PERF_TYPE_TRACEPOINT &&
 		    (int)evsel->attr.config == id)
 			return evsel;
@@ -331,7 +319,7 @@ perf_evlist__find_tracepoint_by_name(struct perf_evlist *evlist,
 {
 	struct perf_evsel *evsel;
 
-	evlist__for_each(evlist, evsel) {
+	evlist__for_each_entry(evlist, evsel) {
 		if ((evsel->attr.type == PERF_TYPE_TRACEPOINT) &&
 		    (strcmp(evsel->name, name) == 0))
 			return evsel;
@@ -366,7 +354,7 @@ void perf_evlist__disable(struct perf_evlist *evlist)
 {
 	struct perf_evsel *pos;
 
-	evlist__for_each(evlist, pos) {
+	evlist__for_each_entry(evlist, pos) {
 		if (!perf_evsel__is_group_leader(pos) || !pos->fd)
 			continue;
 		perf_evsel__disable(pos);
@@ -379,7 +367,7 @@ void perf_evlist__enable(struct perf_evlist *evlist)
 {
 	struct perf_evsel *pos;
 
-	evlist__for_each(evlist, pos) {
+	evlist__for_each_entry(evlist, pos) {
 		if (!perf_evsel__is_group_leader(pos) || !pos->fd)
 			continue;
 		perf_evsel__enable(pos);
@@ -447,7 +435,7 @@ int perf_evlist__alloc_pollfd(struct perf_evlist *evlist)
 	int nfds = 0;
 	struct perf_evsel *evsel;
 
-	evlist__for_each(evlist, evsel) {
+	evlist__for_each_entry(evlist, evsel) {
 		if (evsel->system_wide)
 			nfds += nr_cpus;
 		else
@@ -461,15 +449,16 @@ int perf_evlist__alloc_pollfd(struct perf_evlist *evlist)
 	return 0;
 }
 
-static int __perf_evlist__add_pollfd(struct perf_evlist *evlist, int fd, int idx)
+static int __perf_evlist__add_pollfd(struct perf_evlist *evlist, int fd,
+				     struct perf_mmap *map, short revent)
 {
-	int pos = fdarray__add(&evlist->pollfd, fd, POLLIN | POLLERR | POLLHUP);
+	int pos = fdarray__add(&evlist->pollfd, fd, revent | POLLERR | POLLHUP);
 	/*
 	 * Save the idx so that when we filter out fds POLLHUP'ed we can
 	 * close the associated evlist->mmap[] entry.
 	 */
 	if (pos >= 0) {
-		evlist->pollfd.priv[pos].idx = idx;
+		evlist->pollfd.priv[pos].ptr = map;
 
 		fcntl(fd, F_SETFL, O_NONBLOCK);
 	}
@@ -479,20 +468,22 @@ static int __perf_evlist__add_pollfd(struct perf_evlist *evlist, int fd, int idx
 
 int perf_evlist__add_pollfd(struct perf_evlist *evlist, int fd)
 {
-	return __perf_evlist__add_pollfd(evlist, fd, -1);
+	return __perf_evlist__add_pollfd(evlist, fd, NULL, POLLIN);
 }
 
-static void perf_evlist__munmap_filtered(struct fdarray *fda, int fd)
+static void perf_evlist__munmap_filtered(struct fdarray *fda, int fd,
+					 void *arg __maybe_unused)
 {
-	struct perf_evlist *evlist = container_of(fda, struct perf_evlist, pollfd);
+	struct perf_mmap *map = fda->priv[fd].ptr;
 
-	perf_evlist__mmap_put(evlist, fda->priv[fd].idx);
+	if (map)
+		perf_mmap__put(map);
 }
 
 int perf_evlist__filter_pollfd(struct perf_evlist *evlist, short revents_and_mask)
 {
 	return fdarray__filter(&evlist->pollfd, revents_and_mask,
-			       perf_evlist__munmap_filtered);
+			       perf_evlist__munmap_filtered, NULL);
 }
 
 int perf_evlist__poll(struct perf_evlist *evlist, int timeout)
@@ -646,8 +637,8 @@ static int perf_evlist__event2id(struct perf_evlist *evlist,
 	return 0;
 }
 
-static struct perf_evsel *perf_evlist__event2evsel(struct perf_evlist *evlist,
-						   union perf_event *event)
+struct perf_evsel *perf_evlist__event2evsel(struct perf_evlist *evlist,
+					    union perf_event *event)
 {
 	struct perf_evsel *first = perf_evlist__first(evlist);
 	struct hlist_head *head;
@@ -679,53 +670,82 @@ static struct perf_evsel *perf_evlist__event2evsel(struct perf_evlist *evlist,
 	return NULL;
 }
 
-union perf_event *perf_evlist__mmap_read(struct perf_evlist *evlist, int idx)
+static int perf_evlist__set_paused(struct perf_evlist *evlist, bool value)
+{
+	int i;
+
+	if (!evlist->backward_mmap)
+		return 0;
+
+	for (i = 0; i < evlist->nr_mmaps; i++) {
+		int fd = evlist->backward_mmap[i].fd;
+		int err;
+
+		if (fd < 0)
+			continue;
+		err = ioctl(fd, PERF_EVENT_IOC_PAUSE_OUTPUT, value ? 1 : 0);
+		if (err)
+			return err;
+	}
+	return 0;
+}
+
+static int perf_evlist__pause(struct perf_evlist *evlist)
+{
+	return perf_evlist__set_paused(evlist, true);
+}
+
+static int perf_evlist__resume(struct perf_evlist *evlist)
+{
+	return perf_evlist__set_paused(evlist, false);
+}
+
+/* When check_messup is true, 'end' must points to a good entry */
+static union perf_event *
+perf_mmap__read(struct perf_mmap *md, bool check_messup, u64 start,
+		u64 end, u64 *prev)
 {
-	struct perf_mmap *md = &evlist->mmap[idx];
-	u64 head;
-	u64 old = md->prev;
 	unsigned char *data = md->base + page_size;
 	union perf_event *event = NULL;
+	int diff = end - start;
 
-	/*
-	 * Check if event was unmapped due to a POLLHUP/POLLERR.
-	 */
-	if (!atomic_read(&md->refcnt))
-		return NULL;
-
-	head = perf_mmap__read_head(md);
-	if (evlist->overwrite) {
+	if (check_messup) {
 		/*
 		 * If we're further behind than half the buffer, there's a chance
 		 * the writer will bite our tail and mess up the samples under us.
 		 *
-		 * If we somehow ended up ahead of the head, we got messed up.
+		 * If we somehow ended up ahead of the 'end', we got messed up.
 		 *
-		 * In either case, truncate and restart at head.
+		 * In either case, truncate and restart at 'end'.
 		 */
-		int diff = head - old;
 		if (diff > md->mask / 2 || diff < 0) {
 			fprintf(stderr, "WARNING: failed to keep up with mmap data.\n");
 
 			/*
-			 * head points to a known good entry, start there.
+			 * 'end' points to a known good entry, start there.
 			 */
-			old = head;
+			start = end;
+			diff = 0;
 		}
 	}
 
-	if (old != head) {
+	if (diff >= (int)sizeof(event->header)) {
 		size_t size;
 
-		event = (union perf_event *)&data[old & md->mask];
+		event = (union perf_event *)&data[start & md->mask];
 		size = event->header.size;
 
+		if (size < sizeof(event->header) || diff < (int)size) {
+			event = NULL;
+			goto broken_event;
+		}
+
 		/*
 		 * Event straddles the mmap boundary -- header should always
 		 * be inside due to u64 alignment of output.
 		 */
-		if ((old & md->mask) + size != ((old + size) & md->mask)) {
-			unsigned int offset = old;
+		if ((start & md->mask) + size != ((start + size) & md->mask)) {
+			unsigned int offset = start;
 			unsigned int len = min(sizeof(*event), size), cpy;
 			void *dst = md->event_copy;
 
@@ -740,44 +760,148 @@ union perf_event *perf_evlist__mmap_read(struct perf_evlist *evlist, int idx)
 			event = (union perf_event *) md->event_copy;
 		}
 
-		old += size;
+		start += size;
 	}
 
-	md->prev = old;
+broken_event:
+	if (prev)
+		*prev = start;
 
 	return event;
 }
 
-static bool perf_mmap__empty(struct perf_mmap *md)
+union perf_event *perf_mmap__read_forward(struct perf_mmap *md, bool check_messup)
 {
-	return perf_mmap__read_head(md) == md->prev && !md->auxtrace_mmap.base;
+	u64 head;
+	u64 old = md->prev;
+
+	/*
+	 * Check if event was unmapped due to a POLLHUP/POLLERR.
+	 */
+	if (!atomic_read(&md->refcnt))
+		return NULL;
+
+	head = perf_mmap__read_head(md);
+
+	return perf_mmap__read(md, check_messup, old, head, &md->prev);
 }
 
-static void perf_evlist__mmap_get(struct perf_evlist *evlist, int idx)
+union perf_event *
+perf_mmap__read_backward(struct perf_mmap *md)
 {
-	atomic_inc(&evlist->mmap[idx].refcnt);
+	u64 head, end;
+	u64 start = md->prev;
+
+	/*
+	 * Check if event was unmapped due to a POLLHUP/POLLERR.
+	 */
+	if (!atomic_read(&md->refcnt))
+		return NULL;
+
+	head = perf_mmap__read_head(md);
+	if (!head)
+		return NULL;
+
+	/*
+	 * 'head' pointer starts from 0. Kernel minus sizeof(record) form
+	 * it each time when kernel writes to it, so in fact 'head' is
+	 * negative. 'end' pointer is made manually by adding the size of
+	 * the ring buffer to 'head' pointer, means the validate data can
+	 * read is the whole ring buffer. If 'end' is positive, the ring
+	 * buffer has not fully filled, so we must adjust 'end' to 0.
+	 *
+	 * However, since both 'head' and 'end' is unsigned, we can't
+	 * simply compare 'end' against 0. Here we compare '-head' and
+	 * the size of the ring buffer, where -head is the number of bytes
+	 * kernel write to the ring buffer.
+	 */
+	if (-head < (u64)(md->mask + 1))
+		end = 0;
+	else
+		end = head + md->mask + 1;
+
+	return perf_mmap__read(md, false, start, end, &md->prev);
 }
 
-static void perf_evlist__mmap_put(struct perf_evlist *evlist, int idx)
+union perf_event *perf_evlist__mmap_read_forward(struct perf_evlist *evlist, int idx)
 {
-	BUG_ON(atomic_read(&evlist->mmap[idx].refcnt) == 0);
+	struct perf_mmap *md = &evlist->mmap[idx];
 
-	if (atomic_dec_and_test(&evlist->mmap[idx].refcnt))
-		__perf_evlist__munmap(evlist, idx);
+	/*
+	 * Check messup is required for forward overwritable ring buffer:
+	 * memory pointed by md->prev can be overwritten in this case.
+	 * No need for read-write ring buffer: kernel stop outputting when
+	 * it hit md->prev (perf_mmap__consume()).
+	 */
+	return perf_mmap__read_forward(md, evlist->overwrite);
 }
 
-void perf_evlist__mmap_consume(struct perf_evlist *evlist, int idx)
+union perf_event *perf_evlist__mmap_read_backward(struct perf_evlist *evlist, int idx)
 {
 	struct perf_mmap *md = &evlist->mmap[idx];
 
-	if (!evlist->overwrite) {
+	/*
+	 * No need to check messup for backward ring buffer:
+	 * We can always read arbitrary long data from a backward
+	 * ring buffer unless we forget to pause it before reading.
+	 */
+	return perf_mmap__read_backward(md);
+}
+
+union perf_event *perf_evlist__mmap_read(struct perf_evlist *evlist, int idx)
+{
+	return perf_evlist__mmap_read_forward(evlist, idx);
+}
+
+void perf_mmap__read_catchup(struct perf_mmap *md)
+{
+	u64 head;
+
+	if (!atomic_read(&md->refcnt))
+		return;
+
+	head = perf_mmap__read_head(md);
+	md->prev = head;
+}
+
+void perf_evlist__mmap_read_catchup(struct perf_evlist *evlist, int idx)
+{
+	perf_mmap__read_catchup(&evlist->mmap[idx]);
+}
+
+static bool perf_mmap__empty(struct perf_mmap *md)
+{
+	return perf_mmap__read_head(md) == md->prev && !md->auxtrace_mmap.base;
+}
+
+static void perf_mmap__get(struct perf_mmap *map)
+{
+	atomic_inc(&map->refcnt);
+}
+
+static void perf_mmap__put(struct perf_mmap *md)
+{
+	BUG_ON(md->base && atomic_read(&md->refcnt) == 0);
+
+	if (atomic_dec_and_test(&md->refcnt))
+		perf_mmap__munmap(md);
+}
+
+void perf_mmap__consume(struct perf_mmap *md, bool overwrite)
+{
+	if (!overwrite) {
 		u64 old = md->prev;
 
 		perf_mmap__write_tail(md, old);
 	}
 
 	if (atomic_read(&md->refcnt) == 1 && perf_mmap__empty(md))
-		perf_evlist__mmap_put(evlist, idx);
+		perf_mmap__put(md);
+}
+
+void perf_evlist__mmap_consume(struct perf_evlist *evlist, int idx)
+{
+	perf_mmap__consume(&evlist->mmap[idx], evlist->overwrite);
 }
 
 int __weak auxtrace_mmap__mmap(struct auxtrace_mmap *mm __maybe_unused,
@@ -808,36 +932,52 @@ void __weak auxtrace_mmap_params__set_idx(
 {
 }
 
-static void __perf_evlist__munmap(struct perf_evlist *evlist, int idx)
+static void perf_mmap__munmap(struct perf_mmap *map)
 {
-	if (evlist->mmap[idx].base != NULL) {
-		munmap(evlist->mmap[idx].base, evlist->mmap_len);
-		evlist->mmap[idx].base = NULL;
-		atomic_set(&evlist->mmap[idx].refcnt, 0);
+	if (map->base != NULL) {
+		munmap(map->base, perf_mmap__mmap_len(map));
+		map->base = NULL;
+		map->fd = -1;
+		atomic_set(&map->refcnt, 0);
 	}
-	auxtrace_mmap__munmap(&evlist->mmap[idx].auxtrace_mmap);
+	auxtrace_mmap__munmap(&map->auxtrace_mmap);
 }
 
-void perf_evlist__munmap(struct perf_evlist *evlist)
+static void perf_evlist__munmap_nofree(struct perf_evlist *evlist)
 {
 	int i;
 
-	if (evlist->mmap == NULL)
-		return;
+	if (evlist->mmap)
+		for (i = 0; i < evlist->nr_mmaps; i++)
+			perf_mmap__munmap(&evlist->mmap[i]);
 
-	for (i = 0; i < evlist->nr_mmaps; i++)
-		__perf_evlist__munmap(evlist, i);
+	if (evlist->backward_mmap)
+		for (i = 0; i < evlist->nr_mmaps; i++)
+			perf_mmap__munmap(&evlist->backward_mmap[i]);
+}
 
+void perf_evlist__munmap(struct perf_evlist *evlist)
+{
+	perf_evlist__munmap_nofree(evlist);
 	zfree(&evlist->mmap);
+	zfree(&evlist->backward_mmap);
 }
 
-static int perf_evlist__alloc_mmap(struct perf_evlist *evlist)
+static struct perf_mmap *perf_evlist__alloc_mmap(struct perf_evlist *evlist)
 {
+	int i;
+	struct perf_mmap *map;
+
 	evlist->nr_mmaps = cpu_map__nr(evlist->cpus);
 	if (cpu_map__empty(evlist->cpus))
 		evlist->nr_mmaps = thread_map__nr(evlist->threads);
-	evlist->mmap = zalloc(evlist->nr_mmaps * sizeof(struct perf_mmap));
-	return evlist->mmap != NULL ? 0 : -ENOMEM;
+	map = zalloc(evlist->nr_mmaps * sizeof(struct perf_mmap));
+	if (!map)
+		return NULL;
+
+	for (i = 0; i < evlist->nr_mmaps; i++)
+		map[i].fd = -1;
+	return map;
 }
 
 struct mmap_params {
@@ -846,8 +986,8 @@ struct mmap_params {
 	struct auxtrace_mmap_params auxtrace_mp;
 };
 
-static int __perf_evlist__mmap(struct perf_evlist *evlist, int idx,
-			       struct mmap_params *mp, int fd)
+static int perf_mmap__mmap(struct perf_mmap *map,
+			   struct mmap_params *mp, int fd)
 {
 	/*
 	 * The last one will be done at perf_evlist__mmap_consume(), so that we
@@ -862,34 +1002,61 @@ static int __perf_evlist__mmap(struct perf_evlist *evlist, int idx,
 	 * evlist layer can't just drop it when filtering events in
 	 * perf_evlist__filter_pollfd().
 	 */
-	atomic_set(&evlist->mmap[idx].refcnt, 2);
-	evlist->mmap[idx].prev = 0;
-	evlist->mmap[idx].mask = mp->mask;
-	evlist->mmap[idx].base = mmap(NULL, evlist->mmap_len, mp->prot,
-				      MAP_SHARED, fd, 0);
-	if (evlist->mmap[idx].base == MAP_FAILED) {
+	atomic_set(&map->refcnt, 2);
+	map->prev = 0;
+	map->mask = mp->mask;
+	map->base = mmap(NULL, perf_mmap__mmap_len(map), mp->prot,
+			 MAP_SHARED, fd, 0);
+	if (map->base == MAP_FAILED) {
 		pr_debug2("failed to mmap perf event ring buffer, error %d\n",
 			  errno);
-		evlist->mmap[idx].base = NULL;
+		map->base = NULL;
 		return -1;
 	}
+	map->fd = fd;
 
-	if (auxtrace_mmap__mmap(&evlist->mmap[idx].auxtrace_mmap,
-				&mp->auxtrace_mp, evlist->mmap[idx].base, fd))
+	if (auxtrace_mmap__mmap(&map->auxtrace_mmap,
+				&mp->auxtrace_mp, map->base, fd))
 		return -1;
 
 	return 0;
 }
 
+static bool
+perf_evlist__should_poll(struct perf_evlist *evlist __maybe_unused,
+			 struct perf_evsel *evsel)
+{
+	if (evsel->attr.write_backward)
+		return false;
+	return true;
+}
+
 static int perf_evlist__mmap_per_evsel(struct perf_evlist *evlist, int idx,
 				       struct mmap_params *mp, int cpu,
-				       int thread, int *output)
+				       int thread, int *_output, int *_output_backward)
 {
 	struct perf_evsel *evsel;
+	int revent;
 
-	evlist__for_each(evlist, evsel) {
+	evlist__for_each_entry(evlist, evsel) {
+		struct perf_mmap *maps = evlist->mmap;
+		int *output = _output;
 		int fd;
 
+		if (evsel->attr.write_backward) {
+			output = _output_backward;
+			maps = evlist->backward_mmap;
+
+			if (!maps) {
+				maps = perf_evlist__alloc_mmap(evlist);
+				if (!maps)
+					return -1;
+				evlist->backward_mmap = maps;
+				if (evlist->bkw_mmap_state == BKW_MMAP_NOTREADY)
+					perf_evlist__toggle_bkw_mmap(evlist, BKW_MMAP_RUNNING);
+			}
+		}
+
 		if (evsel->system_wide && thread)
 			continue;
 
@@ -897,15 +1064,18 @@ static int perf_evlist__mmap_per_evsel(struct perf_evlist *evlist, int idx,
 
 		if (*output == -1) {
 			*output = fd;
-			if (__perf_evlist__mmap(evlist, idx, mp, *output) < 0)
+
+			if (perf_mmap__mmap(&maps[idx], mp, *output)  < 0)
 				return -1;
 		} else {
 			if (ioctl(fd, PERF_EVENT_IOC_SET_OUTPUT, *output) != 0)
 				return -1;
 
-			perf_evlist__mmap_get(evlist, idx);
+			perf_mmap__get(&maps[idx]);
 		}
 
+		revent = perf_evlist__should_poll(evlist, evsel) ? POLLIN : 0;
+
 		/*
 		 * The system_wide flag causes a selected event to be opened
 		 * always without a pid.  Consequently it will never get a
@@ -914,8 +1084,8 @@ static int perf_evlist__mmap_per_evsel(struct perf_evlist *evlist, int idx,
 		 * Therefore don't add it for polling.
 		 */
 		if (!evsel->system_wide &&
-		    __perf_evlist__add_pollfd(evlist, fd, idx) < 0) {
-			perf_evlist__mmap_put(evlist, idx);
+		    __perf_evlist__add_pollfd(evlist, fd, &maps[idx], revent) < 0) {
+			perf_mmap__put(&maps[idx]);
 			return -1;
 		}
 
@@ -941,13 +1111,14 @@ static int perf_evlist__mmap_per_cpu(struct perf_evlist *evlist,
 	pr_debug2("perf event ring buffer mmapped per cpu\n");
 	for (cpu = 0; cpu < nr_cpus; cpu++) {
 		int output = -1;
+		int output_backward = -1;
 
 		auxtrace_mmap_params__set_idx(&mp->auxtrace_mp, evlist, cpu,
 					      true);
 
 		for (thread = 0; thread < nr_threads; thread++) {
 			if (perf_evlist__mmap_per_evsel(evlist, cpu, mp, cpu,
-							thread, &output))
+							thread, &output, &output_backward))
 				goto out_unmap;
 		}
 	}
@@ -955,8 +1126,7 @@ static int perf_evlist__mmap_per_cpu(struct perf_evlist *evlist,
 	return 0;
 
 out_unmap:
-	for (cpu = 0; cpu < nr_cpus; cpu++)
-		__perf_evlist__munmap(evlist, cpu);
+	perf_evlist__munmap_nofree(evlist);
 	return -1;
 }
 
@@ -969,43 +1139,51 @@ static int perf_evlist__mmap_per_thread(struct perf_evlist *evlist,
 	pr_debug2("perf event ring buffer mmapped per thread\n");
 	for (thread = 0; thread < nr_threads; thread++) {
 		int output = -1;
+		int output_backward = -1;
 
 		auxtrace_mmap_params__set_idx(&mp->auxtrace_mp, evlist, thread,
 					      false);
 
 		if (perf_evlist__mmap_per_evsel(evlist, thread, mp, 0, thread,
-						&output))
+						&output, &output_backward))
 			goto out_unmap;
 	}
 
 	return 0;
 
 out_unmap:
-	for (thread = 0; thread < nr_threads; thread++)
-		__perf_evlist__munmap(evlist, thread);
+	perf_evlist__munmap_nofree(evlist);
 	return -1;
 }
 
-static size_t perf_evlist__mmap_size(unsigned long pages)
+unsigned long perf_event_mlock_kb_in_pages(void)
 {
-	if (pages == UINT_MAX) {
-		int max;
+	unsigned long pages;
+	int max;
 
-		if (sysctl__read_int("kernel/perf_event_mlock_kb", &max) < 0) {
-			/*
-			 * Pick a once upon a time good value, i.e. things look
-			 * strange since we can't read a sysctl value, but lets not
-			 * die yet...
-			 */
-			max = 512;
-		} else {
-			max -= (page_size / 1024);
-		}
+	if (sysctl__read_int("kernel/perf_event_mlock_kb", &max) < 0) {
+		/*
+		 * Pick a once upon a time good value, i.e. things look
+		 * strange since we can't read a sysctl value, but lets not
+		 * die yet...
+		 */
+		max = 512;
+	} else {
+		max -= (page_size / 1024);
+	}
+
+	pages = (max * 1024) / page_size;
+	if (!is_power_of_2(pages))
+		pages = rounddown_pow_of_two(pages);
 
-		pages = (max * 1024) / page_size;
-		if (!is_power_of_2(pages))
-			pages = rounddown_pow_of_two(pages);
-	} else if (!is_power_of_2(pages))
+	return pages;
+}
+
+static size_t perf_evlist__mmap_size(unsigned long pages)
+{
+	if (pages == UINT_MAX)
+		pages = perf_event_mlock_kb_in_pages();
+	else if (!is_power_of_2(pages))
 		return 0;
 
 	return (pages + 1) * page_size;
@@ -1107,7 +1285,9 @@ int perf_evlist__mmap_ex(struct perf_evlist *evlist, unsigned int pages,
 		.prot = PROT_READ | (overwrite ? 0 : PROT_WRITE),
 	};
 
-	if (evlist->mmap == NULL && perf_evlist__alloc_mmap(evlist) < 0)
+	if (!evlist->mmap)
+		evlist->mmap = perf_evlist__alloc_mmap(evlist);
+	if (!evlist->mmap)
 		return -ENOMEM;
 
 	if (evlist->pollfd.entries == NULL && perf_evlist__alloc_pollfd(evlist) < 0)
@@ -1121,7 +1301,7 @@ int perf_evlist__mmap_ex(struct perf_evlist *evlist, unsigned int pages,
 	auxtrace_mmap_params__init(&mp.auxtrace_mp, evlist->mmap_len,
 				   auxtrace_pages, auxtrace_overwrite);
 
-	evlist__for_each(evlist, evsel) {
+	evlist__for_each_entry(evlist, evsel) {
 		if ((evsel->attr.read_format & PERF_FORMAT_ID) &&
 		    evsel->sample_id == NULL &&
 		    perf_evsel__alloc_id(evsel, cpu_map__nr(cpus), threads->nr) < 0)
@@ -1192,6 +1372,24 @@ void perf_evlist__set_maps(struct perf_evlist *evlist, struct cpu_map *cpus,
 	perf_evlist__propagate_maps(evlist);
 }
 
+void __perf_evlist__set_sample_bit(struct perf_evlist *evlist,
+				   enum perf_event_sample_format bit)
+{
+	struct perf_evsel *evsel;
+
+	evlist__for_each_entry(evlist, evsel)
+		__perf_evsel__set_sample_bit(evsel, bit);
+}
+
+void __perf_evlist__reset_sample_bit(struct perf_evlist *evlist,
+				     enum perf_event_sample_format bit)
+{
+	struct perf_evsel *evsel;
+
+	evlist__for_each_entry(evlist, evsel)
+		__perf_evsel__reset_sample_bit(evsel, bit);
+}
+
 int perf_evlist__apply_filters(struct perf_evlist *evlist, struct perf_evsel **err_evsel)
 {
 	struct perf_evsel *evsel;
@@ -1199,7 +1397,7 @@ int perf_evlist__apply_filters(struct perf_evlist *evlist, struct perf_evsel **e
 	const int ncpus = cpu_map__nr(evlist->cpus),
 		  nthreads = thread_map__nr(evlist->threads);
 
-	evlist__for_each(evlist, evsel) {
+	evlist__for_each_entry(evlist, evsel) {
 		if (evsel->filter == NULL)
 			continue;
 
@@ -1222,7 +1420,7 @@ int perf_evlist__set_filter(struct perf_evlist *evlist, const char *filter)
 	struct perf_evsel *evsel;
 	int err = 0;
 
-	evlist__for_each(evlist, evsel) {
+	evlist__for_each_entry(evlist, evsel) {
 		if (evsel->attr.type != PERF_TYPE_TRACEPOINT)
 			continue;
 
@@ -1276,7 +1474,7 @@ bool perf_evlist__valid_sample_type(struct perf_evlist *evlist)
 	if (evlist->id_pos < 0 || evlist->is_pos < 0)
 		return false;
 
-	evlist__for_each(evlist, pos) {
+	evlist__for_each_entry(evlist, pos) {
 		if (pos->id_pos != evlist->id_pos ||
 		    pos->is_pos != evlist->is_pos)
 			return false;
@@ -1292,7 +1490,7 @@ u64 __perf_evlist__combined_sample_type(struct perf_evlist *evlist)
 	if (evlist->combined_sample_type)
 		return evlist->combined_sample_type;
 
-	evlist__for_each(evlist, evsel)
+	evlist__for_each_entry(evlist, evsel)
 		evlist->combined_sample_type |= evsel->attr.sample_type;
 
 	return evlist->combined_sample_type;
@@ -1309,7 +1507,7 @@ u64 perf_evlist__combined_branch_type(struct perf_evlist *evlist)
 	struct perf_evsel *evsel;
 	u64 branch_type = 0;
 
-	evlist__for_each(evlist, evsel)
+	evlist__for_each_entry(evlist, evsel)
 		branch_type |= evsel->attr.branch_sample_type;
 	return branch_type;
 }
@@ -1320,7 +1518,7 @@ bool perf_evlist__valid_read_format(struct perf_evlist *evlist)
 	u64 read_format = first->attr.read_format;
 	u64 sample_type = first->attr.sample_type;
 
-	evlist__for_each(evlist, pos) {
+	evlist__for_each_entry(evlist, pos) {
 		if (read_format != pos->attr.read_format)
 			return false;
 	}
@@ -1377,7 +1575,7 @@ bool perf_evlist__valid_sample_id_all(struct perf_evlist *evlist)
 {
 	struct perf_evsel *first = perf_evlist__first(evlist), *pos = first;
 
-	evlist__for_each_continue(evlist, pos) {
+	evlist__for_each_entry_continue(evlist, pos) {
 		if (first->attr.sample_id_all != pos->attr.sample_id_all)
 			return false;
 	}
@@ -1404,7 +1602,7 @@ void perf_evlist__close(struct perf_evlist *evlist)
 	int nthreads = thread_map__nr(evlist->threads);
 	int n;
 
-	evlist__for_each_reverse(evlist, evsel) {
+	evlist__for_each_entry_reverse(evlist, evsel) {
 		n = evsel->cpus ? evsel->cpus->nr : ncpus;
 		perf_evsel__close(evsel, n, nthreads);
 	}
@@ -1458,7 +1656,7 @@ int perf_evlist__open(struct perf_evlist *evlist)
 
 	perf_evlist__update_id_pos(evlist);
 
-	evlist__for_each(evlist, evsel) {
+	evlist__for_each_entry(evlist, evsel) {
 		err = perf_evsel__open(evsel, evsel->cpus, evsel->threads);
 		if (err < 0)
 			goto out_err;
@@ -1619,7 +1817,7 @@ size_t perf_evlist__fprintf(struct perf_evlist *evlist, FILE *fp)
 	struct perf_evsel *evsel;
 	size_t printed = 0;
 
-	evlist__for_each(evlist, evsel) {
+	evlist__for_each_entry(evlist, evsel) {
 		printed += fprintf(fp, "%s%s", evsel->idx ? ", " : "",
 				   perf_evsel__name(evsel));
 	}
@@ -1631,7 +1829,7 @@ int perf_evlist__strerror_open(struct perf_evlist *evlist,
 			       int err, char *buf, size_t size)
 {
 	int printed, value;
-	char sbuf[STRERR_BUFSIZE], *emsg = strerror_r(err, sbuf, sizeof(sbuf));
+	char sbuf[STRERR_BUFSIZE], *emsg = str_error_r(err, sbuf, sizeof(sbuf));
 
 	switch (err) {
 	case EACCES:
@@ -1683,7 +1881,7 @@ out_default:
 
 int perf_evlist__strerror_mmap(struct perf_evlist *evlist, int err, char *buf, size_t size)
 {
-	char sbuf[STRERR_BUFSIZE], *emsg = strerror_r(err, sbuf, sizeof(sbuf));
+	char sbuf[STRERR_BUFSIZE], *emsg = str_error_r(err, sbuf, sizeof(sbuf));
 	int pages_attempted = evlist->mmap_len / 1024, pages_max_per_user, printed = 0;
 
 	switch (err) {
@@ -1721,7 +1919,7 @@ void perf_evlist__to_front(struct perf_evlist *evlist,
 	if (move_evsel == perf_evlist__first(evlist))
 		return;
 
-	evlist__for_each_safe(evlist, n, evsel) {
+	evlist__for_each_entry_safe(evlist, n, evsel) {
 		if (evsel->leader == move_evsel->leader)
 			list_move_tail(&evsel->node, &move);
 	}
@@ -1737,7 +1935,7 @@ void perf_evlist__set_tracking_event(struct perf_evlist *evlist,
 	if (tracking_evsel->tracking)
 		return;
 
-	evlist__for_each(evlist, evsel) {
+	evlist__for_each_entry(evlist, evsel) {
 		if (evsel != tracking_evsel)
 			evsel->tracking = false;
 	}
@@ -1751,7 +1949,7 @@ perf_evlist__find_evsel_by_str(struct perf_evlist *evlist,
 {
 	struct perf_evsel *evsel;
 
-	evlist__for_each(evlist, evsel) {
+	evlist__for_each_entry(evlist, evsel) {
 		if (!evsel->name)
 			continue;
 		if (strcmp(str, evsel->name) == 0)
@@ -1760,3 +1958,61 @@ perf_evlist__find_evsel_by_str(struct perf_evlist *evlist,
 
 	return NULL;
 }
+
+void perf_evlist__toggle_bkw_mmap(struct perf_evlist *evlist,
+				  enum bkw_mmap_state state)
+{
+	enum bkw_mmap_state old_state = evlist->bkw_mmap_state;
+	enum action {
+		NONE,
+		PAUSE,
+		RESUME,
+	} action = NONE;
+
+	if (!evlist->backward_mmap)
+		return;
+
+	switch (old_state) {
+	case BKW_MMAP_NOTREADY: {
+		if (state != BKW_MMAP_RUNNING)
+			goto state_err;;
+		break;
+	}
+	case BKW_MMAP_RUNNING: {
+		if (state != BKW_MMAP_DATA_PENDING)
+			goto state_err;
+		action = PAUSE;
+		break;
+	}
+	case BKW_MMAP_DATA_PENDING: {
+		if (state != BKW_MMAP_EMPTY)
+			goto state_err;
+		break;
+	}
+	case BKW_MMAP_EMPTY: {
+		if (state != BKW_MMAP_RUNNING)
+			goto state_err;
+		action = RESUME;
+		break;
+	}
+	default:
+		WARN_ONCE(1, "Shouldn't get there\n");
+	}
+
+	evlist->bkw_mmap_state = state;
+
+	switch (action) {
+	case PAUSE:
+		perf_evlist__pause(evlist);
+		break;
+	case RESUME:
+		perf_evlist__resume(evlist);
+		break;
+	case NONE:
+	default:
+		break;
+	}
+
+state_err:
+	return;
+}