On Fri, 9 Sep 2016, Chen Yu wrote:
> > I really have no idea why this is burried in x86 land. The pm_trace hackery
> > issues mc146818_set_time() to fiddle with the RTC. So any implementation of
> > this is affected.
> OK, I've changed this patch according to this suggestion.
No you did not! You still have that silly x86 hackery in place.
> OK. I've moved most of the logic into the pm_trace component,
> Once the mc146818_set_time has modified the RTC by pm_trace,
> related flags will be set which indicates the unusable of RTC.
> And timekeeping system is able to query these flags to decide whether
> it should inject the sleep time. (We tried to make this patch as
> simple as possible, but it looks like we have to deal with persistent
> clock for x86, which makes this patch a little more complicated).
> Here's the trial version of it, any suggestion would be appreciated:
It's overengineered and horrible.
> +unsigned int timekeeping_tainted;
It does not taint timekeeping. It just wreckages the RTC.
> +void pm_trace_taint_timekeeping(void)
> +{
> + if (pm_trace_is_enabled()) {
> + timekeeping_tainted |= TIMEKEEPING_RTC_TAINTED;
> + if (arch_pm_trace_taint_pclock())
> + timekeeping_tainted |=
> TIMEKEEPING_PERSISTENT_CLOCK_TAINTED;
> + }
Why would you need all these flags?
> +static inline int pm_trace_rtc_is_tainted(void)
> +{
> + return (timekeeping_tainted & TIMEKEEPING_RTC_TAINTED) ?
> + 1 : 0;
ever heard about bool?
> +}
> +
> +extern void pm_trace_untaint_timekeeping(void);
And how exactly do you untaint it? Just by clearing the flags. That makes
the RTC time magically correct again?
> +int arch_pm_trace_taint_pclock(void)
> +{
> + return (x86_platform.get_wallclock == mach_get_cmos_time);
> +}
Groan. I told you to do it in the mc14xxx related places. There are not
that many in the kernel
Here is a completely uncompiled/untested patch which should address the
issue in a halfways clean way.
Thanks,
tglx
--- a/arch/x86/kernel/rtc.c
+++ b/arch/x86/kernel/rtc.c
@@ -64,6 +64,15 @@ void mach_get_cmos_time(struct timespec
unsigned int status, year, mon, day, hour, min, sec, century = 0;
unsigned long flags;
+ /*
+ * If pm trace abused the RTC as storage set the timespec to 0
+ * which tells the caller that this RTC value is bogus.
+ */
+ if (!pm_trace_rtc_valid()) {
+ now->tv_sec = now->tv_nsec = 0;
+ return;
+ }
+
spin_lock_irqsave(&rtc_lock, flags);
/*
--- a/drivers/base/power/trace.c
+++ b/drivers/base/power/trace.c
@@ -74,6 +74,7 @@
#define DEVSEED (7919)
+bool pm_trace_rtc_abused __read_mostly;
static unsigned int dev_hash_value;
static int set_magic_time(unsigned int user, unsigned int file, unsigned int
device)
@@ -104,6 +105,7 @@ static int set_magic_time(unsigned int u
time.tm_min = (n % 20) * 3;
n /= 20;
mc146818_set_time(&time);
+ pm_trace_rtc_abused = true;
return n ? -1 : 0;
}
--- a/drivers/rtc/rtc-cmos.c
+++ b/drivers/rtc/rtc-cmos.c
@@ -189,6 +189,13 @@ static inline void cmos_write_bank2(unsi
static int cmos_read_time(struct device *dev, struct rtc_time *t)
{
+ /*
+ * If pmtrace abused the RTC for storage tell the caller that it is
+ * unusable.
+ */
+ if (!pm_trace_rtc_valid())
+ return -EIO;
+
/* REVISIT: if the clock has a "century" register, use
* that instead of the heuristic in mc146818_get_time().
* That'll make Y3K compatility (year > 2070) easy!
--- a/include/linux/mc146818rtc.h
+++ b/include/linux/mc146818rtc.h
@@ -16,6 +16,7 @@
#include <asm/mc146818rtc.h> /* register access macros */
#include <linux/bcd.h>
#include <linux/delay.h>
+#include <linux/pm-trace.h>
#ifdef __KERNEL__
#include <linux/spinlock.h> /* spinlock_t */
--- a/include/linux/pm-trace.h
+++ b/include/linux/pm-trace.h
@@ -6,6 +6,12 @@
#include <linux/types.h>
extern int pm_trace_enabled;
+extern bool pm_trace_rtc_abused;
+
+static inline bool pm_trace_rtc_valid(void)
+{
+ return !pm_trace_rtc_abused;
+}
static inline int pm_trace_is_enabled(void)
{
@@ -24,6 +30,7 @@ extern int show_trace_dev_match(char *bu
#else
+static inline bool pm_trace_rtc_valid(void) { return true; }
static inline int pm_trace_is_enabled(void) { return 0; }
#define TRACE_DEVICE(dev) do { } while (0)
