[Xen-devel] [PATCH V2] tools/xenstore-watch: Add new timeout parameter

[Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>]

This patch allows xenstore-watch to exit even if no changes to its
XenStore key have occured in a specified interval (in seconds), via
a new -T parameter.

Signed-off-by: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>

---
Changes since V1:
 - Exiting the timeout loop even on EINTR.
---
 tools/xenstore/xenstore_client.c | 64 ++++++++++++++++++++++++++++++----------
 1 file changed, 48 insertions(+), 16 deletions(-)

diff --git a/tools/xenstore/xenstore_client.c b/tools/xenstore/xenstore_client.c
index 3d14d37..6788158 100644
--- a/tools/xenstore/xenstore_client.c
+++ b/tools/xenstore/xenstore_client.c
@@ -12,6 +12,7 @@
 #include <errno.h>
 #include <fcntl.h>
 #include <getopt.h>
+#include <poll.h>
 #include <stdarg.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -99,7 +100,7 @@ usage(enum mode mode, int incl_mode, const char *progname)
        errx(1, "Usage: %s %s[-h] [-u] [-r] [-s] key <mode [modes...]>", 
progname, mstr);
     case MODE_watch:
        mstr = incl_mode ? "watch " : "";
-       errx(1, "Usage: %s %s[-h] [-n NR] key", progname, mstr);
+       errx(1, "Usage: %s %s[-h] [-n NR] [-T TIMEOUT] key", progname, mstr);
     }
 }
 
@@ -273,27 +274,49 @@ do_chmod(char *path, struct xs_permissions *perms, int 
nperms, int upto,
 }
 
 static void
-do_watch(struct xs_handle *xsh, int max_events)
+do_watch(struct xs_handle *xsh, int max_events, int timeout)
 {
-    int count = 0;
+    int rc, ms_timeout = timeout * 1000;
     char **vec = NULL;
+    struct pollfd fd;
 
-    for ( count = 0; max_events == -1 || count < max_events; count++ ) {
-       unsigned int num;
+    fd.fd = xs_fileno(xsh);
+    fd.events = POLLIN | POLLERR;
 
-       vec = xs_read_watch(xsh, &num);
-       if (vec == NULL)
-           continue;
+    do {
+        rc = poll(&fd, 1, 100);
 
-       printf("%s\n", vec[XS_WATCH_PATH]);
-       fflush(stdout);
-       free(vec);
-    }
+        if (rc == 0) {
+            ms_timeout -= 100;
+            continue;
+        }
+
+        if (rc < 0) {
+            err(1, "poll() failed: %s", strerror(errno));
+            return;
+        }
+
+        if (fd.revents & POLLIN) {
+            unsigned int num;
+
+            --max_events;
+            vec = xs_read_watch(xsh, &num);
+
+            if (vec == NULL)
+                continue;
+
+            printf("%s\n", vec[XS_WATCH_PATH]);
+            fflush(stdout);
+            free(vec);
+        }
+
+    } while ((ms_timeout > 0 || timeout == -1) && max_events > 0);
 }
 
 static int
 perform(enum mode mode, int optind, int argc, char **argv, struct xs_handle 
*xsh,
-        xs_transaction_t xth, int prefix, int tidy, int upto, int recurse, int 
nr_watches)
+        xs_transaction_t xth, int prefix, int tidy, int upto, int recurse, int 
nr_watches,
+        int timeout)
 {
     switch (mode) {
     case MODE_ls:
@@ -461,7 +484,7 @@ perform(enum mode mode, int optind, int argc, char **argv, 
struct xs_handle *xsh
                 if (!xs_watch(xsh, w, w))
                     errx(1, "Unable to add watch on %s\n", w);
             }
-            do_watch(xsh, nr_watches);
+            do_watch(xsh, nr_watches, timeout);
         }
         }
     }
@@ -505,6 +528,7 @@ main(int argc, char **argv)
     int upto = 0;
     int recurse = 0;
     int nr_watches = -1;
+    int timeout = -1;
     int transaction;
     struct winsize ws;
     enum mode mode;
@@ -539,10 +563,11 @@ main(int argc, char **argv)
            {"upto",    0, 0, 'u'}, /* MODE_chmod */
            {"recurse", 0, 0, 'r'}, /* MODE_chmod */
            {"number",  1, 0, 'n'}, /* MODE_watch */
+           {"timeout", 1, 0, 'T'}, /* MODE_watch */
            {0, 0, 0, 0}
        };
 
-       c = getopt_long(argc - switch_argv, argv + switch_argv, "hfspturn:",
+       c = getopt_long(argc - switch_argv, argv + switch_argv, "hfspturn:T:",
                        long_options, &index);
        if (c == -1)
            break;
@@ -593,6 +618,12 @@ main(int argc, char **argv)
            else
                usage(mode, switch_argv, argv[0]);
            break;
+       case 'T':
+           if ( mode == MODE_watch )
+               timeout = atoi(optarg);
+           else
+               usage(mode, switch_argv, argv[0]);
+           break;
        }
     }
 
@@ -646,7 +677,8 @@ again:
            errx(1, "couldn't start transaction");
     }
 
-    ret = perform(mode, optind, argc - switch_argv, argv + switch_argv, xsh, 
xth, prefix, tidy, upto, recurse, nr_watches);
+    ret = perform(mode, optind, argc - switch_argv, argv + switch_argv, xsh, 
xth, prefix, tidy, upto, recurse,
+                  nr_watches, timeout);
 
     if (transaction && !xs_transaction_end(xsh, xth, ret)) {
        if (ret == 0 && errno == EAGAIN) {
-- 
1.9.1


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