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-rw-r--r--src/vppinfra/time.c20
1 files changed, 20 insertions, 0 deletions
diff --git a/src/vppinfra/time.c b/src/vppinfra/time.c
index e9a764bcd31..d647e670dad 100644
--- a/src/vppinfra/time.c
+++ b/src/vppinfra/time.c
@@ -197,6 +197,7 @@ clib_time_verify_frequency (clib_time_t * c)
f64 dtr = now_reference - c->last_verify_reference_time;
f64 dtr_max;
u64 dtc = c->last_cpu_time - c->last_verify_cpu_time;
+ f64 new_clocks_per_second, delta;
f64 round_units = 100e5;
c->last_verify_cpu_time = c->last_cpu_time;
@@ -217,6 +218,25 @@ clib_time_verify_frequency (clib_time_t * c)
return;
}
+ /*
+ * Reject large frequency changes, another consequence of
+ * system clock changes particularly with old kernels.
+ */
+ new_clocks_per_second =
+ flt_round_nearest ((f64) dtc / (dtr * round_units)) * round_units;
+
+ delta = new_clocks_per_second - c->clocks_per_second;
+ if (delta < 0.0)
+ delta = -delta;
+
+ if (PREDICT_FALSE ((delta / c->clocks_per_second) > .01))
+ {
+ clib_warning ("Rejecting large frequency change of %.2f%%",
+ (delta / c->clocks_per_second) * 100.0);
+ c->log2_clocks_per_frequency_verify = c->log2_clocks_per_second;
+ return;
+ }
+
c->clocks_per_second =
flt_round_nearest ((f64) dtc / (dtr * round_units)) * round_units;
c->seconds_per_clock = 1 / c->clocks_per_second;