From 77da5b6144566b3a4a78fa41a114fa62630f682b Mon Sep 17 00:00:00 2001
From: Richard Curnow <rc@rc0.org.uk>
Date: Tue, 19 Jul 2005 21:22:52 +0000
Subject: [PATCH] RTC usage bails out cleanly if accessing it goes wrong (e.g.
 HPET without generic RTC emulation)

---
 NEWS        |  8 ++++++++
 chrony.texi |  6 +++++-
 rtc_linux.c | 12 +++++++++++-
 3 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/NEWS b/NEWS
index 4131859..f3cc5f2 100644
--- a/NEWS
+++ b/NEWS
@@ -1,3 +1,11 @@
+New in version 1.21
+===================
+
+* Don't include Linux kernel header files any longer : allows chrony to compile
+  on recent distros.
+* Stop trying to use RTC if continuous streams of error messages would occur
+  (Linux with HPET).
+
 New in version 1.20
 ===================
 
diff --git a/chrony.texi b/chrony.texi
index 4642bb7..909a0cc 100644
--- a/chrony.texi
+++ b/chrony.texi
@@ -836,7 +836,11 @@ compiled into the kernel).  An estimate is made of the RTC error at a
 particular RTC second, and the rate at which the RTC gains or loses time
 relative to true time.
 
-The RTC is fully supported in 2.2 and 2.4 kernels.
+The RTC is fully supported in 2.2, 2.4 and 2.6 kernels.
+
+On 2.6 kernels, if your motherboard has a HPET, you need to enable the
+@samp{HPET_EMULATE_RTC} option in your kernel configuration.  Otherwise, chrony
+will not be able to interact with the RTC device and will give up using it.
 
 For kernels in the 2.0 series prior to 2.0.32, the kernel was set up to
 trim the RTC every 11 minutes.  This would be disasterous for
diff --git a/rtc_linux.c b/rtc_linux.c
index 4b4ca18..8765a12 100644
--- a/rtc_linux.c
+++ b/rtc_linux.c
@@ -867,9 +867,19 @@ read_from_device(void *any)
 
   status = read(fd, &data, sizeof(data));
   if (status < 0) {
+    /* This looks like a bad error : the file descriptor was indicating it was
+     * ready to read but we couldn't read anything.  Give up. */
     LOG(LOGS_ERR, LOGF_RtcLinux, "Could not read flags %s : %s", CNF_GetRtcDevice(), strerror(errno));
     error = 1;
-    goto turn_off_interrupt;
+    SCH_RemoveInputFileHandler(fd);
+    switch_interrupts(0); /* Likely to raise error too, but just to be sure... */
+    close(fd);
+    fd = -1;
+    if (logfile) {
+      fclose(logfile);
+      logfile = NULL;
+    }
+    return;
   }    
 
   if ((data & RTC_UIE) == RTC_UIE) {