Implement adding of file descriptors to fixed size (currently 1)
storage at struct fdarray by the dedicated fdarray__add_stat().
Append the static descriptors to the array used by poll() syscall
at fdarray__poll(). Copy poll() result of the descriptors from the
array back to the storage for possible later analysis separately
from descriptors added by fdarray__add().

Signed-off-by: Alexey Budankov <alexey.budan...@linux.intel.com>
---
 tools/lib/api/fd/array.c                 | 42 +++++++++++++++++++++++-
 tools/lib/api/fd/array.h                 |  7 ++++
 tools/lib/perf/evlist.c                  | 11 +++++++
 tools/lib/perf/include/internal/evlist.h |  2 ++
 4 files changed, 61 insertions(+), 1 deletion(-)

diff --git a/tools/lib/api/fd/array.c b/tools/lib/api/fd/array.c
index 58d44d5eee31..b0027f2169c7 100644
--- a/tools/lib/api/fd/array.c
+++ b/tools/lib/api/fd/array.c
@@ -11,10 +11,16 @@
 
 void fdarray__init(struct fdarray *fda, int nr_autogrow)
 {
+       int i;
+
        fda->entries     = NULL;
        fda->priv        = NULL;
        fda->nr          = fda->nr_alloc = 0;
        fda->nr_autogrow = nr_autogrow;
+
+       fda->nr_stat = 0;
+       for (i = 0; i < FDARRAY__STAT_ENTRIES_MAX; i++)
+               fda->stat_entries[i].fd = -1;
 }
 
 int fdarray__grow(struct fdarray *fda, int nr)
@@ -83,6 +89,20 @@ int fdarray__add(struct fdarray *fda, int fd, short revents)
        return pos;
 }
 
+int fdarray__add_stat(struct fdarray *fda, int fd, short revents)
+{
+       int pos = fda->nr_stat;
+
+       if (pos >= FDARRAY__STAT_ENTRIES_MAX)
+               return -1;
+
+       fda->stat_entries[pos].fd = fd;
+       fda->stat_entries[pos].events = revents;
+       fda->nr_stat++;
+
+       return pos;
+}
+
 int fdarray__filter(struct fdarray *fda, short revents,
                    void (*entry_destructor)(struct fdarray *fda, int fd, void 
*arg),
                    void *arg)
@@ -113,7 +133,27 @@ int fdarray__filter(struct fdarray *fda, short revents,
 
 int fdarray__poll(struct fdarray *fda, int timeout)
 {
-       return poll(fda->entries, fda->nr, timeout);
+       int nr, i, pos, res;
+
+       nr = fda->nr;
+
+       for (i = 0; i < fda->nr_stat; i++) {
+               if (fda->stat_entries[i].fd != -1) {
+                       pos = fdarray__add(fda, fda->stat_entries[i].fd,
+                                          fda->stat_entries[i].events);
+                       if (pos >= 0)
+                               fda->priv[pos].idx = i;
+               }
+       }
+
+       res = poll(fda->entries, fda->nr, timeout);
+
+       for (i = nr; i < fda->nr; i++)
+               fda->stat_entries[fda->priv[i].idx] = fda->entries[i];
+
+       fda->nr = nr;
+
+       return res;
 }
 
 int fdarray__fprintf(struct fdarray *fda, FILE *fp)
diff --git a/tools/lib/api/fd/array.h b/tools/lib/api/fd/array.h
index b39557d1a88f..9bca72e80b09 100644
--- a/tools/lib/api/fd/array.h
+++ b/tools/lib/api/fd/array.h
@@ -3,6 +3,7 @@
 #define __API_FD_ARRAY__
 
 #include <stdio.h>
+#include <poll.h>
 
 struct pollfd;
 
@@ -16,6 +17,9 @@ struct pollfd;
  *       I.e. using 'fda->priv[N].idx = * value' where N < fda->nr is ok,
  *       but doing 'fda->priv = malloc(M)' is not allowed.
  */
+
+#define FDARRAY__STAT_ENTRIES_MAX      1
+
 struct fdarray {
        int            nr;
        int            nr_alloc;
@@ -25,6 +29,8 @@ struct fdarray {
                int    idx;
                void   *ptr;
        } *priv;
+       int            nr_stat;
+       struct pollfd  stat_entries[FDARRAY__STAT_ENTRIES_MAX];
 };
 
 void fdarray__init(struct fdarray *fda, int nr_autogrow);
@@ -34,6 +40,7 @@ struct fdarray *fdarray__new(int nr_alloc, int nr_autogrow);
 void fdarray__delete(struct fdarray *fda);
 
 int fdarray__add(struct fdarray *fda, int fd, short revents);
+int fdarray__add_stat(struct fdarray *fda, int fd, short revents);
 int fdarray__poll(struct fdarray *fda, int timeout);
 int fdarray__filter(struct fdarray *fda, short revents,
                    void (*entry_destructor)(struct fdarray *fda, int fd, void 
*arg),
diff --git a/tools/lib/perf/evlist.c b/tools/lib/perf/evlist.c
index 6a875a0f01bb..e68e4c08e7c2 100644
--- a/tools/lib/perf/evlist.c
+++ b/tools/lib/perf/evlist.c
@@ -317,6 +317,17 @@ int perf_evlist__add_pollfd(struct perf_evlist *evlist, 
int fd,
        return pos;
 }
 
+int perf_evlist__add_pollfd_stat(struct perf_evlist *evlist, int fd,
+                                short revent)
+{
+       int pos = fdarray__add_stat(&evlist->pollfd, fd, revent | POLLERR | 
POLLHUP);
+
+       if (pos >= 0)
+               fcntl(fd, F_SETFL, O_NONBLOCK);
+
+       return pos;
+}
+
 static void perf_evlist__munmap_filtered(struct fdarray *fda, int fd,
                                         void *arg __maybe_unused)
 {
diff --git a/tools/lib/perf/include/internal/evlist.h 
b/tools/lib/perf/include/internal/evlist.h
index 74dc8c3f0b66..2b3b4518c05e 100644
--- a/tools/lib/perf/include/internal/evlist.h
+++ b/tools/lib/perf/include/internal/evlist.h
@@ -46,6 +46,8 @@ struct perf_evlist_mmap_ops {
 int perf_evlist__alloc_pollfd(struct perf_evlist *evlist);
 int perf_evlist__add_pollfd(struct perf_evlist *evlist, int fd,
                            void *ptr, short revent);
+int perf_evlist__add_pollfd_stat(struct perf_evlist *evlist, int fd,
+                                short revent);
 
 int perf_evlist__mmap_ops(struct perf_evlist *evlist,
                          struct perf_evlist_mmap_ops *ops,
-- 
2.24.1


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