[Xen-devel] [PATCH] replacing gettimeofday with clock_gettime in xenconsoled

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

Hi all,
currently if someone changes the date on the host, xenconsoled may behave
incorrectly due to the use of gettimeofday for the rate control algorithm.
For example I was able to hang the console connected to a guest just setting
the date forward 20 years.
To solve the problem we need to use a time source that doesn't change start
point, that is clock_gettime with CLOCK_MONOTONIC.
The only bad side effect is that it introduces a dependency to librt, but I
think is well worth it.

Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>

---

diff -r a538185695ed tools/console/Makefile
--- a/tools/console/Makefile    Tue Jul 29 15:10:58 2008 +0100
+++ b/tools/console/Makefile    Tue Jul 29 15:47:29 2008 +0100
@@ -21,7 +21,7 @@ clean:
 
 xenconsoled: $(patsubst %.c,%.o,$(wildcard daemon/*.c))
        $(CC) $(CFLAGS) $^ -o $@ $(LDFLAGS) \
-              $(UTIL_LIBS) $(SOCKET_LIBS)
+              $(UTIL_LIBS) $(SOCKET_LIBS) -lrt
 
 xenconsole: $(patsubst %.c,%.o,$(wildcard client/*.c))
        $(CC) $(CFLAGS) $^ -o $@ $(LDFLAGS) \
diff -r a538185695ed tools/console/daemon/io.c
--- a/tools/console/daemon/io.c Tue Jul 29 15:10:58 2008 +0100
+++ b/tools/console/daemon/io.c Tue Jul 29 15:44:59 2008 +0100
@@ -622,9 +622,9 @@ static struct domain *create_domain(int 
 {
        struct domain *dom;
        char *s;
-       struct timeval tv;
-
-       if (gettimeofday(&tv, NULL) < 0) {
+       struct timespec ts;
+
+       if (clock_gettime(CLOCK_MONOTONIC, &ts) < 0) {
                dolog(LOG_ERR, "Cannot get time of day %s:%s:L%d",
                      __FILE__, __FUNCTION__, __LINE__);
                return NULL;
@@ -666,7 +666,7 @@ static struct domain *create_domain(int 
        dom->buffer.capacity = 0;
        dom->buffer.max_capacity = 0;
        dom->event_count = 0;
-       dom->next_period = (tv.tv_sec * 1000) + (tv.tv_usec / 1000) + 
RATE_LIMIT_PERIOD;
+       dom->next_period = (ts.tv_sec * 1000) + (ts.tv_nsec / 1000000) + 
RATE_LIMIT_PERIOD;
        dom->next = NULL;
 
        dom->ring_ref = -1;
@@ -971,7 +971,7 @@ void handle_io(void)
                struct domain *d, *n;
                int max_fd = -1;
                struct timeval timeout;
-               struct timeval tv;
+               struct timespec ts;
                long long now, next_timeout = 0;
 
                FD_ZERO(&readfds);
@@ -985,9 +985,9 @@ void handle_io(void)
                        max_fd = MAX(xc_evtchn_fd(xce_handle), max_fd);
                }
 
-               if (gettimeofday(&tv, NULL) < 0)
+               if (clock_gettime(CLOCK_MONOTONIC, &ts) < 0)
                        return;
-               now = (tv.tv_sec * 1000) + (tv.tv_usec / 1000);
+               now = (ts.tv_sec * 1000) + (ts.tv_nsec / 1000000);
 
                /* Re-calculate any event counter allowances & unblock
                   domains with new allowance */

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