[RFC,v2,2/9] time: Provide y2106 safe get_seconds() replacement

Message ID 1421163897-8020-3-git-send-email-xlpang@126.com
State New
Headers show

Commit Message

Xunlei Pang Jan. 13, 2015, 3:44 p.m.
From: Xunlei Pang <pang.xunlei@linaro.org>

As part of addressing "y2038 problem" for in-kernel uses, this
patch adds safe get_seconds64() using time64_t.

After this patch, get_seconds() is deprecated and all its call sites
will be fixed using get_seconds64(), after that it can be removed.

Signed-off-by: Xunlei Pang <pang.xunlei@linaro.org>
---
 include/linux/timekeeping.h | 10 +++++++++-
 kernel/time/timekeeping.c   |  4 ++--
 2 files changed, 11 insertions(+), 3 deletions(-)

Comments

pang.xunlei Jan. 14, 2015, 2:52 p.m. | #1
On 14 January 2015 at 04:42, Thomas Gleixner <tglx@linutronix.de> wrote:
> On Tue, 13 Jan 2015, Xunlei Pang wrote:
>
>> From: Xunlei Pang <pang.xunlei@linaro.org>
>>
>> As part of addressing "y2038 problem" for in-kernel uses, this
>> patch adds safe get_seconds64() using time64_t.
>>
>> After this patch, get_seconds() is deprecated and all its call sites
>> will be fixed using get_seconds64(), after that it can be removed.
>
> Why another interface?
>
> We already have ktime_get_real_seconds(). That handles 32bit
> correctly, while your new function does not.
>
> You cannot return a 64bit value unprotected against updates on 32bit,
> unless you want to implement a RNG.

Yes, ktime_get_real_seconds() should be used instead.

Thanks,
Xunlei
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Patch

diff --git a/include/linux/timekeeping.h b/include/linux/timekeeping.h
index 9b63d13..384d101 100644
--- a/include/linux/timekeeping.h
+++ b/include/linux/timekeeping.h
@@ -17,7 +17,7 @@  extern int do_sys_settimeofday(const struct timespec *tv,
 /*
  * Kernel time accessors
  */
-unsigned long get_seconds(void);
+extern time64_t get_seconds64(void);
 struct timespec current_kernel_time(void);
 /* does not take xtime_lock */
 struct timespec __current_kernel_time(void);
@@ -34,6 +34,14 @@  extern time64_t ktime_get_real_seconds(void);
 extern int __getnstimeofday64(struct timespec64 *tv);
 extern void getnstimeofday64(struct timespec64 *tv);
 
+/**
+ * Deprecated. Use get_seconds64().
+ */
+static inline unsigned long get_seconds(void)
+{
+	return (unsigned long)get_seconds64();
+}
+
 #if BITS_PER_LONG == 64
 /**
  * Deprecated. Use do_settimeofday64().
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 6a93185..ab021a3 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -1678,13 +1678,13 @@  void getboottime(struct timespec *ts)
 }
 EXPORT_SYMBOL_GPL(getboottime);
 
-unsigned long get_seconds(void)
+time64_t get_seconds64(void)
 {
 	struct timekeeper *tk = &tk_core.timekeeper;
 
 	return tk->xtime_sec;
 }
-EXPORT_SYMBOL(get_seconds);
+EXPORT_SYMBOL(get_seconds64);
 
 struct timespec __current_kernel_time(void)
 {