Use rtc_lock to protect RTC operations

    
Many RTC routines were not protected against each other, so there are
potential races, for example, ntp-update against /dev/rtc.  This patch
fixes them using rtc_lock.
    
Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

2 files changed, 25 insertions, 2 deletions

diff --git a/include/asm-mips/mc146818-time.h b/include/asm-mips/mc146818-time.h
index a2c2d2c24303..47214861093b 100644
--- a/include/asm-mips/mc146818-time.h
+++ b/include/asm-mips/mc146818-time.h
@@ -33,7 +33,9 @@ static inline int mc146818_set_rtc_mmss(unsigned long nowtime)
         int real_seconds, real_minutes, cmos_minutes;
         unsigned char save_control, save_freq_select;
         int retval = 0;
+        unsigned long flags;
 
+        spin_lock_irqsave(&rtc_lock, flags);
         save_control = CMOS_READ(RTC_CONTROL); /* tell the clock it's being set */
         CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL);
 
@@ -79,14 +81,30 @@ static inline int mc146818_set_rtc_mmss(unsigned long nowtime)
          */
         CMOS_WRITE(save_control, RTC_CONTROL);
         CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
+        spin_unlock_irqrestore(&rtc_lock, flags);
 
         return retval;
 }
 
+/*
+ * Returns true if a clock update is in progress
+ */
+static inline unsigned char rtc_is_updating(void)
+{
+        unsigned char uip;
+        unsigned long flags;
+
+        spin_lock_irqsave(&rtc_lock, flags);
+        uip = (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP);
+        spin_unlock_irqrestore(&rtc_lock, flags);
+        return uip;
+}
+
 static inline unsigned long mc146818_get_cmos_time(void)
 {
         unsigned int year, mon, day, hour, min, sec;
         int i;
+        unsigned long flags;
 
         /*
          * The Linux interpretation of the CMOS clock register contents:
@@ -97,12 +115,13 @@ static inline unsigned long mc146818_get_cmos_time(void)
 
         /* read RTC exactly on falling edge of update flag */
         for (i = 0 ; i < 1000000 ; i++) /* may take up to 1 second... */
-                if (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP)
+                if (rtc_is_updating())
                         break;
         for (i = 0 ; i < 1000000 ; i++) /* must try at least 2.228 ms */
-                if (!(CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP))
+                if (!rtc_is_updating())
                         break;
 
+        spin_lock_irqsave(&rtc_lock, flags);
         do { /* Isn't this overkill ? UIP above should guarantee consistency */
                 sec = CMOS_READ(RTC_SECONDS);
                 min = CMOS_READ(RTC_MINUTES);
@@ -120,6 +139,7 @@ static inline unsigned long mc146818_get_cmos_time(void)
                 BCD_TO_BIN(mon);
                 BCD_TO_BIN(year);
         }
+        spin_unlock_irqrestore(&rtc_lock, flags);
         year = mc146818_decode_year(year);
 
         return mktime(year, mon, day, hour, min, sec);
diff --git a/include/asm-mips/time.h b/include/asm-mips/time.h
index e22a20665871..9cc3564cc2c9 100644
--- a/include/asm-mips/time.h
+++ b/include/asm-mips/time.h
@@ -20,6 +20,9 @@
 #include <linux/linkage.h>
 #include <linux/ptrace.h>
 #include <linux/rtc.h>
+#include <linux/spinlock.h>
+
+extern spinlock_t rtc_lock;
 
 /*
  * RTC ops.  By default, they point to no-RTC functions.