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authorJohn Stultz <john.stultz@linaro.org>2012-09-11 19:26:03 -0400
committerIngo Molnar <mingo@kernel.org>2012-09-13 17:39:14 +0200
commitec145babe754f9ea1079034a108104b6001e001c (patch)
tree2b65fdc6916989cacdc2bbcc94a48ef847eae099 /kernel/time/timekeeping.c
parent0bd1189e239c76eb3a50e458548fbe7e4a5dfff1 (diff)
downloadlinaro-lsk-ec145babe754f9ea1079034a108104b6001e001c.tar.gz
time: Fix timeekeping_get_ns overflow on 32bit systems
Daniel Lezcano reported seeing multi-second stalls from keyboard input on his T61 laptop when NOHZ and CPU_IDLE were enabled on a 32bit kernel. He bisected the problem down to commit 1e75fa8be9fb6 ("time: Condense timekeeper.xtime into xtime_sec"). After reproducing this issue, I narrowed the problem down to the fact that timekeeping_get_ns() returns a 64bit nsec value that hasn't been accumulated. In some cases this value was being then stored in timespec.tv_nsec (which is a long). On 32bit systems, with idle times larger then 4 seconds (or less, depending on the value of xtime_nsec), the returned nsec value would overflow 32bits. This limited kept time from increasing, causing timers to not expire. The fix is to make sure we don't directly store the result of timekeeping_get_ns() into a tv_nsec field, instead using a 64bit nsec value which can then be added into the timespec via timespec_add_ns(). Reported-and-bisected-by: Daniel Lezcano <daniel.lezcano@linaro.org> Tested-by: Daniel Lezcano <daniel.lezcano@linaro.org> Signed-off-by: John Stultz <john.stultz@linaro.org> Acked-by: Prarit Bhargava <prarit@redhat.com> Cc: Richard Cochran <richardcochran@gmail.com> Link: http://lkml.kernel.org/r/1347405963-35715-1-git-send-email-john.stultz@linaro.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/time/timekeeping.c')
-rw-r--r--kernel/time/timekeeping.c19
1 files changed, 12 insertions, 7 deletions
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 34e5eac8142..d3b91e75cec 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -303,10 +303,11 @@ void getnstimeofday(struct timespec *ts)
seq = read_seqbegin(&tk->lock);
ts->tv_sec = tk->xtime_sec;
- ts->tv_nsec = timekeeping_get_ns(tk);
+ nsecs = timekeeping_get_ns(tk);
} while (read_seqretry(&tk->lock, seq));
+ ts->tv_nsec = 0;
timespec_add_ns(ts, nsecs);
}
EXPORT_SYMBOL(getnstimeofday);
@@ -345,6 +346,7 @@ void ktime_get_ts(struct timespec *ts)
{
struct timekeeper *tk = &timekeeper;
struct timespec tomono;
+ s64 nsec;
unsigned int seq;
WARN_ON(timekeeping_suspended);
@@ -352,13 +354,14 @@ void ktime_get_ts(struct timespec *ts)
do {
seq = read_seqbegin(&tk->lock);
ts->tv_sec = tk->xtime_sec;
- ts->tv_nsec = timekeeping_get_ns(tk);
+ nsec = timekeeping_get_ns(tk);
tomono = tk->wall_to_monotonic;
} while (read_seqretry(&tk->lock, seq));
- set_normalized_timespec(ts, ts->tv_sec + tomono.tv_sec,
- ts->tv_nsec + tomono.tv_nsec);
+ ts->tv_sec += tomono.tv_sec;
+ ts->tv_nsec = 0;
+ timespec_add_ns(ts, nsec + tomono.tv_nsec);
}
EXPORT_SYMBOL_GPL(ktime_get_ts);
@@ -1244,6 +1247,7 @@ void get_monotonic_boottime(struct timespec *ts)
{
struct timekeeper *tk = &timekeeper;
struct timespec tomono, sleep;
+ s64 nsec;
unsigned int seq;
WARN_ON(timekeeping_suspended);
@@ -1251,14 +1255,15 @@ void get_monotonic_boottime(struct timespec *ts)
do {
seq = read_seqbegin(&tk->lock);
ts->tv_sec = tk->xtime_sec;
- ts->tv_nsec = timekeeping_get_ns(tk);
+ nsec = timekeeping_get_ns(tk);
tomono = tk->wall_to_monotonic;
sleep = tk->total_sleep_time;
} while (read_seqretry(&tk->lock, seq));
- set_normalized_timespec(ts, ts->tv_sec + tomono.tv_sec + sleep.tv_sec,
- ts->tv_nsec + tomono.tv_nsec + sleep.tv_nsec);
+ ts->tv_sec += tomono.tv_sec + sleep.tv_sec;
+ ts->tv_nsec = 0;
+ timespec_add_ns(ts, nsec + tomono.tv_nsec + sleep.tv_nsec);
}
EXPORT_SYMBOL_GPL(get_monotonic_boottime);