linux/kernel/time/timekeeping.c, branch v3.6

time: Fix timeekeping_get_ns overflow on 32bit systems

2012-09-13T15:39:14Z

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 Tested-by: Daniel Lezcano Signed-off-by: John Stultz Acked-by: Prarit Bhargava Cc: Richard Cochran Link: http://lkml.kernel.org/r/1347405963-35715-1-git-send-email-john.stultz@linaro.org Signed-off-by: Ingo Molnar

time: Move ktime_t overflow checking into timespec_valid_strict

2012-09-01T17:24:48Z

Andreas Bombe reported that the added ktime_t overflow checking added to timespec_valid in commit 4e8b14526ca7 ("time: Improve sanity checking of timekeeping inputs") was causing problems with X.org because it caused timeouts larger then KTIME_T to be invalid. Previously, these large timeouts would be clamped to KTIME_MAX and would never expire, which is valid. This patch splits the ktime_t overflow checking into a new timespec_valid_strict function, and converts the timekeeping codes internal checking to use this more strict function. Reported-and-tested-by: Andreas Bombe Cc: Zhouping Liu Cc: Ingo Molnar Cc: Prarit Bhargava Cc: Thomas Gleixner Cc: stable@vger.kernel.org Signed-off-by: John Stultz Signed-off-by: Linus Torvalds

time: Avoid making adjustments if we haven't accumulated anything

2012-08-22T08:42:13Z

If update_wall_time() is called and the current offset isn't large enough to accumulate, avoid re-calling timekeeping_adjust which may change the clock freq and can cause 1ns inconsistencies with CLOCK_REALTIME_COARSE/CLOCK_MONOTONIC_COARSE. Signed-off-by: John Stultz Cc: Prarit Bhargava Cc: Ingo Molnar Cc: stable@vger.kernel.org Link: http://lkml.kernel.org/r/1345595449-34965-5-git-send-email-john.stultz@linaro.org Signed-off-by: Thomas Gleixner

time: Avoid potential shift overflow with large shift values

2012-08-22T08:42:13Z

Andreas Schwab noticed that the 1 << tk->shift could overflow if the shift value was greater than 30, since 1 would be a 32bit long on 32bit architectures. This issue was introduced by 1e75fa8be (time: Condense timekeeper.xtime into xtime_sec) Use 1ULL instead to ensure we don't overflow on the shift. Reported-by: Andreas Schwab Signed-off-by: John Stultz Cc: Prarit Bhargava Cc: Ingo Molnar Link: http://lkml.kernel.org/r/1345595449-34965-4-git-send-email-john.stultz@linaro.org Signed-off-by: Thomas Gleixner

time: Fix casting issue in timekeeping_forward_now

2012-08-22T08:42:13Z

arch_gettimeoffset returns a u32 value which when shifted by tk->shift can overflow. This issue was introduced with 1e75fa8be (time: Condense timekeeper.xtime into xtime_sec) Cast it to u64 first. Signed-off-by: Andreas Schwab Signed-off-by: John Stultz Cc: Prarit Bhargava Cc: Ingo Molnar Link: http://lkml.kernel.org/r/1345595449-34965-3-git-send-email-john.stultz@linaro.org Signed-off-by: Thomas Gleixner

time: Ensure we normalize the timekeeper in tk_xtime_add

2012-08-22T08:42:12Z

Andreas noticed problems with resume on specific hardware after commit 1e75fa8b (time: Condense timekeeper.xtime into xtime_sec) combined with commit b44d50dca (time: Fix casting issue in tk_set_xtime and tk_xtime_add) After some digging I realized we aren't normalizing the timekeeper after the add. Add the missing normalize call. Reported-by: Andreas Schwab Tested-by: Andreas Schwab Signed-off-by: John Stultz Cc: Prarit Bhargava Cc: Ingo Molnar Link: http://lkml.kernel.org/r/1345595449-34965-2-git-send-email-john.stultz@linaro.org Signed-off-by: Thomas Gleixner

time: Improve sanity checking of timekeeping inputs

2012-08-15T13:54:01Z

Unexpected behavior could occur if the time is set to a value large enough to overflow a 64bit ktime_t (which is something larger then the year 2262). Also unexpected behavior could occur if large negative offsets are injected via adjtimex. So this patch improves the sanity check timekeeping inputs by improving the timespec_valid() check, and then makes better use of timespec_valid() to make sure we don't set the time to an invalid negative value or one that overflows ktime_t. Note: This does not protect from setting the time close to overflowing ktime_t and then letting natural accumulation cause the overflow. Reported-by: CAI Qian Reported-by: Sasha Levin Signed-off-by: John Stultz Cc: Peter Zijlstra Cc: Prarit Bhargava Cc: Zhouping Liu Cc: Ingo Molnar Cc: stable@vger.kernel.org Link: http://lkml.kernel.org/r/1344454580-17031-1-git-send-email-john.stultz@linaro.org Signed-off-by: Thomas Gleixner

time: Fix adjustment cleanup bug in timekeeping_adjust()

2012-08-05T10:37:14Z

Tetsuo Handa reported that sporadically the system clock starts counting up too quickly which is enough to confuse the hangcheck timer to print a bogus stall warning. Commit 2a8c0883 "time: Move xtime_nsec adjustment underflow handling timekeeping_adjust" overlooked this exit path: } else return; which should really be a proper exit sequence, fixing the bug as a side effect. Also make the flow more readable by properly balancing curly braces. Reported-by: Tetsuo Handa wrote: Tested-by: Tetsuo Handa wrote: Signed-off-by: Ingo Molnar Cc: john.stultz@linaro.org Cc: a.p.zijlstra@chello.nl Cc: richardcochran@gmail.com Cc: prarit@redhat.com Link: http://lkml.kernel.org/r/20120804192114.GA28347@gmail.com Signed-off-by: Ingo Molnar

time: Remove all direct references to timekeeper

2012-07-31T15:09:14Z

Ingo noted that the numerous timekeeper.value references made the timekeeping code ugly and caused many long lines that had to be broken up. He recommended replacing timekeeper.value references with tk->value. This patch provides a local tk value for all top level time functions and sets it to &timekeeper. Then all timekeeper access is done via a tk pointer. Signed-off-by: John Stultz Cc: Prarit Bhargava Link: http://lkml.kernel.org/r/1343414893-45779-6-git-send-email-john.stultz@linaro.org Signed-off-by: Ingo Molnar

time: Clean up offs_real/wall_to_mono and offs_boot/total_sleep_time updates

2012-07-31T15:09:14Z

For performance reasons, we maintain ktime_t based duplicates of wall_to_monotonic (offs_real) and total_sleep_time (offs_boot). Since large problems could occur (such as the resume regression on 3.5-rc7, or the leapsecond hrtimer issue) if these value pairs were to be inconsistently updated, this patch this cleans up how we modify these value pairs to ensure we are always consistent. As a side-effect this is also more efficient as we only caulculate the duplicate values when they are changed, rather then every update_wall_time call. This also provides WARN_ONs to detect if future changes break the invariants. Signed-off-by: John Stultz Cc: Peter Zijlstra Cc: Richard Cochran Cc: Prarit Bhargava Link: http://lkml.kernel.org/r/1343414893-45779-5-git-send-email-john.stultz@linaro.org [ Cleaned up minor style issues. ] Signed-off-by: Ingo Molnar