user/sven/linux.git/kernel/time, branch v3.18.40

posix_cpu_timer: Exit early when process has been reaped

2016-08-08T01:47:27Z

[ Upstream commit 2c13ce8f6b2f6fd9ba2f9261b1939fc0f62d1307 ] Variable "now" seems to be genuinely used unintialized if branch if (CPUCLOCK_PERTHREAD(timer->it_clock)) { is not taken and branch if (unlikely(sighand == NULL)) { is taken. In this case the process has been reaped and the timer is marked as disarmed anyway. So none of the postprocessing of the sample is required. Return right away. Signed-off-by: Alexey Dobriyan Cc: stable@vger.kernel.org Link: http://lkml.kernel.org/r/20160707223911.GA26483@p183.telecom.by Signed-off-by: Thomas Gleixner Signed-off-by: Sasha Levin

timers: Use proper base migration in add_timer_on()

2016-05-16T13:29:12Z

[ Upstream commit 22b886dd1018093920c4250dee2a9a3cb7cff7b8 ] Regardless of the previous CPU a timer was on, add_timer_on() currently simply sets timer->flags to the new CPU. As the caller must be seeing the timer as idle, this is locally fine, but the timer leaving the old base while unlocked can lead to race conditions as follows. Let's say timer was on cpu 0. cpu 0 cpu 1 ----------------------------------------------------------------------------- del_timer(timer) succeeds del_timer(timer) lock_timer_base(timer) locks cpu_0_base add_timer_on(timer, 1) spin_lock(&cpu_1_base->lock) timer->flags set to cpu_1_base operates on @timer operates on @timer This triggered with mod_delayed_work_on() which contains "if (del_timer()) add_timer_on()" sequence eventually leading to the following oops. BUG: unable to handle kernel NULL pointer dereference at (null) IP: [] detach_if_pending+0x69/0x1a0 ... Workqueue: wqthrash wqthrash_workfunc [wqthrash] task: ffff8800172ca680 ti: ffff8800172d0000 task.ti: ffff8800172d0000 RIP: 0010:[] [] detach_if_pending+0x69/0x1a0 ... Call Trace: [] del_timer+0x44/0x60 [] try_to_grab_pending+0xb6/0x160 [] mod_delayed_work_on+0x33/0x80 [] wqthrash_workfunc+0x61/0x90 [wqthrash] [] process_one_work+0x1e8/0x650 [] worker_thread+0x4e/0x450 [] kthread+0xef/0x110 [] ret_from_fork+0x3f/0x70 Fix it by updating add_timer_on() to perform proper migration as __mod_timer() does. Reported-and-tested-by: Jeff Layton Signed-off-by: Tejun Heo Cc: Chris Worley Cc: bfields@fieldses.org Cc: Michael Skralivetsky Cc: Trond Myklebust Cc: Shaohua Li Cc: Jeff Layton Cc: kernel-team@fb.com Cc: stable@vger.kernel.org Link: http://lkml.kernel.org/r/20151029103113.2f893924@tlielax.poochiereds.net Link: http://lkml.kernel.org/r/20151104171533.GI5749@mtj.duckdns.org Signed-off-by: Thomas Gleixner Signed-off-by: Konstantin Khlebnikov ( backport for 3.18 ) Signed-off-by: Sasha Levin

posix-clock: Fix return code on the poll method's error path

2016-02-10T03:55:43Z

[ Upstream commit 1b9f23727abb92c5e58f139e7d180befcaa06fe0 ] The posix_clock_poll function is supposed to return a bit mask of POLLxxx values. However, in case the hardware has disappeared (due to hot plugging for example) this code returns -ENODEV in a futile attempt to throw an error at the file descriptor level. The kernel's file_operations interface does not accept such error codes from the poll method. Instead, this function aught to return POLLERR. The value -ENODEV does, in fact, contain the POLLERR bit (and almost all the other POLLxxx bits as well), but only by chance. This patch fixes code to return a proper bit mask. Credit goes to Markus Elfring for pointing out the suspicious signed/unsigned mismatch. Reported-by: Markus Elfring igned-off-by: Richard Cochran Cc: John Stultz Cc: Julia Lawall Link: http://lkml.kernel.org/r/1450819198-17420-1-git-send-email-richardcochran@gmail.com Cc: stable@vger.kernel.org Signed-off-by: Thomas Gleixner Signed-off-by: Sasha Levin

time: Avoid signed overflow in timekeeping_get_ns()

2016-02-02T18:53:36Z

[ Upstream commit 35a4933a895927990772ae96fdcfd2f806929ee2 ] 1e75fa8 "time: Condense timekeeper.xtime into xtime_sec" replaced a call to clocksource_cyc2ns() from timekeeping_get_ns() with an open-coded version of the same logic to avoid keeping a semi-redundant struct timespec in struct timekeeper. However, the commit also introduced a subtle semantic change - where clocksource_cyc2ns() uses purely unsigned math, the new version introduces a signed temporary, meaning that if (delta * tk->mult) has a 63-bit overflow the following shift will still give a negative result. The choice of 'maxsec' in __clocksource_updatefreq_scale() means this will generally happen if there's a ~10 minute pause in examining the clocksource. This can be triggered on a powerpc KVM guest by stopping it from qemu for a bit over 10 minutes. After resuming time has jumped backwards several minutes causing numerous problems (jiffies does not advance, msleep()s can be extended by minutes..). It doesn't happen on x86 KVM guests, because the guest TSC is effectively frozen while the guest is stopped, which is not the case for the powerpc timebase. Obviously an unsigned (64 bit) overflow will only take twice as long as a signed, 63-bit overflow. I don't know the time code well enough to know if that will still cause incorrect calculations, or if a 64-bit overflow is avoided elsewhere. Still, an incorrect forwards clock adjustment will cause less trouble than time going backwards. So, this patch removes the potential for intermediate signed overflow. Cc: stable@vger.kernel.org (3.7+) Suggested-by: Laurent Vivier Tested-by: Laurent Vivier Signed-off-by: David Gibson Signed-off-by: John Stultz Signed-off-by: Sasha Levin

time: Fix timekeeping_freqadjust()'s incorrect use of abs() instead of abs64()

2015-10-28T02:12:51Z

[ Upstream commit 2619d7e9c92d524cb155ec89fd72875321512e5b ] The internal clocksteering done for fine-grained error correction uses a logarithmic approximation, so any time adjtimex() adjusts the clock steering, timekeeping_freqadjust() quickly approximates the correct clock frequency over a series of ticks. Unfortunately, the logic in timekeeping_freqadjust(), introduced in commit: dc491596f639 ("timekeeping: Rework frequency adjustments to work better w/ nohz") used the abs() function with a s64 error value to calculate the size of the approximated adjustment to be made. Per include/linux/kernel.h: "abs() should not be used for 64-bit types (s64, u64, long long) - use abs64()". Thus on 32-bit platforms, this resulted in the clocksteering to take a quite dampended random walk trying to converge on the proper frequency, which caused the adjustments to be made much slower then intended (most easily observed when large adjustments are made). This patch fixes the issue by using abs64() instead. Reported-by: Nuno Gonçalves Tested-by: Nuno Goncalves Signed-off-by: John Stultz Cc: # v3.17+ Cc: Linus Torvalds Cc: Miroslav Lichvar Cc: Peter Zijlstra Cc: Prarit Bhargava Cc: Richard Cochran Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1441840051-20244-1-git-send-email-john.stultz@linaro.org Signed-off-by: Ingo Molnar Signed-off-by: Sasha Levin

ktime: Fix ktime_divns to do signed division

2015-06-09T17:43:50Z

[ Upstream commit f7bcb70ebae0dcdb5a2d859b09e4465784d99029 ] It was noted that the 32bit implementation of ktime_divns() was doing unsigned division and didn't properly handle negative values. And when a ktime helper was changed to utilize ktime_divns, it caused a regression on some IR blasters. See the following bugzilla for details: https://bugzilla.redhat.com/show_bug.cgi?id=1200353 This patch fixes the problem in ktime_divns by checking and preserving the sign bit, and then reapplying it if appropriate after the division, it also changes the return type to a s64 to make it more obvious this is expected. Nicolas also pointed out that negative dividers would cause infinite loops on 32bit systems, negative dividers is unlikely for users of this function, but out of caution this patch adds checks for negative dividers for both 32-bit (BUG_ON) and 64-bit(WARN_ON) versions to make sure no such use cases creep in. [ tglx: Hand an u64 to do_div() to avoid the compiler warning ] Fixes: 166afb64511e 'ktime: Sanitize ktime_to_us/ms conversion' Reported-and-tested-by: Trevor Cordes Signed-off-by: John Stultz Acked-by: Nicolas Pitre Cc: Ingo Molnar Cc: Josh Boyer Cc: One Thousand Gnomes Cc: Link: http://lkml.kernel.org/r/1431118043-23452-1-git-send-email-john.stultz@linaro.org Signed-off-by: Thomas Gleixner Signed-off-by: Sasha Levin

ktime: Optimize ktime_divns for constant divisors

2015-06-09T17:43:49Z

[ Upstream commit 8b618628b2bf83512fc8df5e8672619d65adfdfb ] At least on ARM, do_div() is optimized to turn constant divisors into an inline multiplication by the reciprocal value at compile time. However this optimization is missed entirely whenever ktime_divns() is used and the slow out-of-line division code is used all the time. Let ktime_divns() use do_div() inline whenever the divisor is constant and small enough. This will make things like ktime_to_us() and ktime_to_ms() much faster. Cc: Arnd Bergmann Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Nicolas Pitre Acked-by: Arnd Bergmann Signed-off-by: Nicolas Pitre Signed-off-by: John Stultz Signed-off-by: Sasha Levin

timers/tick/broadcast-hrtimer: Fix suspicious RCU usage in idle loop

2015-04-24T21:14:12Z

[ Upstream commit a127d2bcf1fbc8c8e0b5cf0dab54f7d3ff50ce47 ] The hrtimer mode of broadcast queues hrtimers in the idle entry path so as to wakeup cpus in deep idle states. The associated call graph is : cpuidle_idle_call() |____ clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, ....)) |_____tick_broadcast_set_event() |____clockevents_program_event() |____bc_set_next() The hrtimer_{start/cancel} functions call into tracing which uses RCU. But it is not legal to call into RCU in cpuidle because it is one of the quiescent states. Hence protect this region with RCU_NONIDLE which informs RCU that the cpu is momentarily non-idle. As an aside it is helpful to point out that the clock event device that is programmed here is not a per-cpu clock device; it is a pseudo clock device, used by the broadcast framework alone. The per-cpu clock device programming never goes through bc_set_next(). Signed-off-by: Preeti U Murthy Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Paul E. McKenney Cc: linuxppc-dev@ozlabs.org Cc: mpe@ellerman.id.au Cc: tglx@linutronix.de Link: http://lkml.kernel.org/r/20150318104705.17763.56668.stgit@preeti.in.ibm.com Signed-off-by: Ingo Molnar Signed-off-by: Sasha Levin

ntp: Fixup adjtimex freq validation on 32-bit systems

2015-03-06T22:53:01Z

commit 29183a70b0b828500816bd794b3fe192fce89f73 upstream. Additional validation of adjtimex freq values to avoid potential multiplication overflows were added in commit 5e5aeb4367b (time: adjtimex: Validate the ADJ_FREQUENCY values) Unfortunately the patch used LONG_MAX/MIN instead of LLONG_MAX/MIN, which was fine on 64-bit systems, but being much smaller on 32-bit systems caused false positives resulting in most direct frequency adjustments to fail w/ EINVAL. ntpd only does direct frequency adjustments at startup, so the issue was not as easily observed there, but other time sync applications like ptpd and chrony were more effected by the bug. See bugs: https://bugzilla.kernel.org/show_bug.cgi?id=92481 https://bugzilla.redhat.com/show_bug.cgi?id=1188074 This patch changes the checks to use LLONG_MAX for clarity, and additionally the checks are disabled on 32-bit systems since LLONG_MAX/PPM_SCALE is always larger then the 32-bit long freq value, so multiplication overflows aren't possible there. Reported-by: Josh Boyer Reported-by: George Joseph Tested-by: George Joseph Signed-off-by: John Stultz Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Sasha Levin Link: http://lkml.kernel.org/r/1423553436-29747-1-git-send-email-john.stultz@linaro.org [ Prettified the changelog and the comments a bit. ] Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman

hrtimer: Fix incorrect tai offset calculation for non high-res timer systems

2015-02-11T07:00:56Z

commit 2d926c15d629a13914ce3e5f26354f6a0ac99e70 upstream. I noticed some CLOCK_TAI timer test failures on one of my less-frequently used configurations. And after digging in I found in 76f4108892d9 (Cleanup hrtimer accessors to the timekepeing state), the hrtimer_get_softirq_time tai offset calucation was incorrectly rewritten, as the tai offset we return shold be from CLOCK_MONOTONIC, and not CLOCK_REALTIME. This results in CLOCK_TAI timers expiring early on non-highres capable machines. This patch fixes the issue, calculating the tai time properly from the monotonic base. Signed-off-by: John Stultz Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1423097126-10236-1-git-send-email-john.stultz@linaro.org Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman