Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm

[cascardo/linux.git] / tools / perf / builtin-record.c

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index f3679c4..dc3fcb5 100644 (file)
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -40,6 +40,7 @@
 #include <unistd.h>
 #include <sched.h>
 #include <sys/mman.h>
+#include <asm/bug.h>
 
 
 struct record {
@@ -82,27 +83,87 @@ static int process_synthesized_event(struct perf_tool *tool,
        return record__write(rec, event, event->header.size);
 }
 
+static int
+backward_rb_find_range(void *buf, int mask, u64 head, u64 *start, u64 *end)
+{
+       struct perf_event_header *pheader;
+       u64 evt_head = head;
+       int size = mask + 1;
+
+       pr_debug2("backward_rb_find_range: buf=%p, head=%"PRIx64"\n", buf, head);
+       pheader = (struct perf_event_header *)(buf + (head & mask));
+       *start = head;
+       while (true) {
+               if (evt_head - head >= (unsigned int)size) {
+                       pr_debug("Finshed reading backward ring buffer: rewind\n");
+                       if (evt_head - head > (unsigned int)size)
+                               evt_head -= pheader->size;
+                       *end = evt_head;
+                       return 0;
+               }
+
+               pheader = (struct perf_event_header *)(buf + (evt_head & mask));
+
+               if (pheader->size == 0) {
+                       pr_debug("Finshed reading backward ring buffer: get start\n");
+                       *end = evt_head;
+                       return 0;
+               }
+
+               evt_head += pheader->size;
+               pr_debug3("move evt_head: %"PRIx64"\n", evt_head);
+       }
+       WARN_ONCE(1, "Shouldn't get here\n");
+       return -1;
+}
+
+static int
+rb_find_range(struct perf_evlist *evlist,
+             void *data, int mask, u64 head, u64 old,
+             u64 *start, u64 *end)
+{
+       if (!evlist->backward) {
+               *start = old;
+               *end = head;
+               return 0;
+       }
+
+       return backward_rb_find_range(data, mask, head, start, end);
+}
+
 static int record__mmap_read(struct record *rec, int idx)
 {
        struct perf_mmap *md = &rec->evlist->mmap[idx];
        u64 head = perf_mmap__read_head(md);
        u64 old = md->prev;
+       u64 end = head, start = old;
        unsigned char *data = md->base + page_size;
        unsigned long size;
        void *buf;
        int rc = 0;
 
-       if (old == head)
+       if (rb_find_range(rec->evlist, data, md->mask, head,
+                         old, &start, &end))
+               return -1;
+
+       if (start == end)
                return 0;
 
        rec->samples++;
 
-       size = head - old;
+       size = end - start;
+       if (size > (unsigned long)(md->mask) + 1) {
+               WARN_ONCE(1, "failed to keep up with mmap data. (warn only once)\n");
+
+               md->prev = head;
+               perf_evlist__mmap_consume(rec->evlist, idx);
+               return 0;
+       }
 
-       if ((old & md->mask) + size != (head & md->mask)) {
-               buf = &data[old & md->mask];
-               size = md->mask + 1 - (old & md->mask);
-               old += size;
+       if ((start & md->mask) + size != (end & md->mask)) {
+               buf = &data[start & md->mask];
+               size = md->mask + 1 - (start & md->mask);
+               start += size;
 
                if (record__write(rec, buf, size) < 0) {
                        rc = -1;
@@ -110,16 +171,16 @@ static int record__mmap_read(struct record *rec, int idx)
                }
        }
 
-       buf = &data[old & md->mask];
-       size = head - old;
-       old += size;
+       buf = &data[start & md->mask];
+       size = end - start;
+       start += size;
 
        if (record__write(rec, buf, size) < 0) {
                rc = -1;
                goto out;
        }
 
-       md->prev = old;
+       md->prev = head;
        perf_evlist__mmap_consume(rec->evlist, idx);
 out:
        return rc;