[Xen-devel] [PATCH 13/18] libxl: events: Break out libxl__pipe_nonblock, _close

[Ian Jackson <ian.jackson@xxxxxxxxxxxxx>]

Break out the pipe creation and destruction from the poller code
into two new functions libxl__pipe_nonblock and libxl__pipe_close.
Also change direct use of pipe() to libxl_pipe.

No overall functional difference other than minor differences in exact
log messages.

Also move libxl__self_pipe_wakeup and libxl__self_pipe_eatall into the
new pipe utilities section in libxl_event.c; this is pure code motion.

Signed-off-by: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
Cc: Jim Fehlig <jfehlig@xxxxxxxx>
Cc: Ian Campbell <ian.campbell@xxxxxxxxxx>
Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>

--
v3: Mention that we switched pipe() -> libxl_pipe()
---
 tools/libxl/libxl_event.c    |  104 ++++++++++++++++++++++++++----------------
 tools/libxl/libxl_internal.h |    9 ++++
 2 files changed, 73 insertions(+), 40 deletions(-)

diff --git a/tools/libxl/libxl_event.c b/tools/libxl/libxl_event.c
index 1c48fee..93f8fdc 100644
--- a/tools/libxl/libxl_event.c
+++ b/tools/libxl/libxl_event.c
@@ -1271,26 +1271,81 @@ int libxl_event_check(libxl_ctx *ctx, libxl_event 
**event_r,
 }
 
 /*
- * Manipulation of pollers
+ * Utilities for pipes (specifically, useful for self-pipes)
  */
 
-int libxl__poller_init(libxl_ctx *ctx, libxl__poller *p)
+void libxl__pipe_close(int fds[2])
+{
+    if (fds[0] >= 0) close(fds[0]);
+    if (fds[1] >= 0) close(fds[1]);
+    fds[0] = fds[1] = -1;
+}
+
+int libxl__pipe_nonblock(libxl_ctx *ctx, int fds[2])
 {
     int r, rc;
-    p->fd_polls = 0;
-    p->fd_rindices = 0;
 
-    r = pipe(p->wakeup_pipe);
+    r = libxl_pipe(ctx, fds);
     if (r) {
-        LIBXL__LOG_ERRNO(ctx, LIBXL__LOG_ERROR, "cannot create poller pipe");
+        fds[0] = fds[1] = -1;
         rc = ERROR_FAIL;
         goto out;
     }
 
-    rc = libxl_fd_set_nonblock(ctx, p->wakeup_pipe[0], 1);
+    rc = libxl_fd_set_nonblock(ctx, fds[0], 1);
     if (rc) goto out;
 
-    rc = libxl_fd_set_nonblock(ctx, p->wakeup_pipe[1], 1);
+    rc = libxl_fd_set_nonblock(ctx, fds[1], 1);
+    if (rc) goto out;
+
+    return 0;
+
+ out:
+    libxl__pipe_close(fds);
+    return rc;
+}
+
+int libxl__self_pipe_wakeup(int fd)
+{
+    static const char buf[1] = "";
+
+    for (;;) {
+        int r = write(fd, buf, 1);
+        if (r==1) return 0;
+        assert(r==-1);
+        if (errno == EINTR) continue;
+        if (errno == EWOULDBLOCK) return 0;
+        assert(errno);
+        return errno;
+    }
+}
+
+int libxl__self_pipe_eatall(int fd)
+{
+    char buf[256];
+    for (;;) {
+        int r = read(fd, buf, sizeof(buf));
+        if (r == sizeof(buf)) continue;
+        if (r >= 0) return 0;
+        assert(r == -1);
+        if (errno == EINTR) continue;
+        if (errno == EWOULDBLOCK) return 0;
+        assert(errno);
+        return errno;
+    }
+}
+
+/*
+ * Manipulation of pollers
+ */
+
+int libxl__poller_init(libxl_ctx *ctx, libxl__poller *p)
+{
+    int rc;
+    p->fd_polls = 0;
+    p->fd_rindices = 0;
+
+    rc = libxl__pipe_nonblock(ctx, p->wakeup_pipe);
     if (rc) goto out;
 
     return 0;
@@ -1302,8 +1357,7 @@ int libxl__poller_init(libxl_ctx *ctx, libxl__poller *p)
 
 void libxl__poller_dispose(libxl__poller *p)
 {
-    if (p->wakeup_pipe[1] > 0) close(p->wakeup_pipe[1]);
-    if (p->wakeup_pipe[0] > 0) close(p->wakeup_pipe[0]);
+    libxl__pipe_close(p->wakeup_pipe);
     free(p->fd_polls);
     free(p->fd_rindices);
 }
@@ -1347,36 +1401,6 @@ void libxl__poller_wakeup(libxl__egc *egc, libxl__poller 
*p)
     if (e) LIBXL__EVENT_DISASTER(egc, "cannot poke watch pipe", e, 0);
 }
 
-int libxl__self_pipe_wakeup(int fd)
-{
-    static const char buf[1] = "";
-
-    for (;;) {
-        int r = write(fd, buf, 1);
-        if (r==1) return 0;
-        assert(r==-1);
-        if (errno == EINTR) continue;
-        if (errno == EWOULDBLOCK) return 0;
-        assert(errno);
-        return errno;
-    }
-}
-
-int libxl__self_pipe_eatall(int fd)
-{
-    char buf[256];
-    for (;;) {
-        int r = read(fd, buf, sizeof(buf));
-        if (r == sizeof(buf)) continue;
-        if (r >= 0) return 0;
-        assert(r == -1);
-        if (errno == EINTR) continue;
-        if (errno == EWOULDBLOCK) return 0;
-        assert(errno);
-        return errno;
-    }
-}
-
 /*
  * Main event loop iteration
  */
diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index 8429448..9d17586 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -509,6 +509,15 @@ _hidden char *libxl__strndup(libxl__gc *gc_opt, const char 
*c, size_t n) NN1;
  * string. (similar to a gc'd dirname(3)). */
 _hidden char *libxl__dirname(libxl__gc *gc_opt, const char *s) NN1;
 
+/* Make a pipe and set both ends nonblocking.  On error, nothing
+ * is left open and both fds[]==-1, and a message is logged.
+ * Useful for self-pipes. */
+_hidden int libxl__pipe_nonblock(libxl_ctx *ctx, int fds[2]);
+/* Closes the pipe fd(s).  Either or both of fds[] may be -1 meaning
+ * `not open'.  Ignores any errors.  Sets fds[] to -1. */
+_hidden void libxl__pipe_close(int fds[2]);
+
+
 /* Each of these logs errors and returns a libxl error code.
  * They do not mind if path is already removed.
  * For _file, path must not be a directory; for _directory it must be. */
-- 
1.7.10.4


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