user/sven/linux.git/kernel/cpu.c, branch v4.14.16

timers: Reinitialize per cpu bases on hotplug

2018-01-02T19:31:15Z

commit 26456f87aca7157c057de65c9414b37f1ab881d1 upstream. The timer wheel bases are not (re)initialized on CPU hotplug. That leaves them with a potentially stale clk and next_expiry valuem, which can cause trouble then the CPU is plugged. Add a prepare callback which forwards the clock, sets next_expiry to far in the future and reset the control flags to a known state. Set base->must_forward_clk so the first timer which is queued will try to forward the clock to current jiffies. Fixes: 500462a9de65 ("timers: Switch to a non-cascading wheel") Reported-by: Paul E. McKenney Signed-off-by: Thomas Gleixner Cc: Peter Zijlstra Cc: Frederic Weisbecker Cc: Sebastian Siewior Cc: Anna-Maria Gleixner Link: https://lkml.kernel.org/r/alpine.DEB.2.20.1712272152200.2431@nanos Signed-off-by: Greg Kroah-Hartman

smp/hotplug: Move step CPUHP_AP_SMPCFD_DYING to the correct place

2017-12-14T08:52:56Z

commit 46febd37f9c758b05cd25feae8512f22584742fe upstream. Commit 31487f8328f2 ("smp/cfd: Convert core to hotplug state machine") accidently put this step on the wrong place. The step should be at the cpuhp_ap_states[] rather than the cpuhp_bp_states[]. grep smpcfd /sys/devices/system/cpu/hotplug/states 40: smpcfd:prepare 129: smpcfd:dying "smpcfd:dying" was missing before. So was the invocation of the function smpcfd_dying_cpu(). Fixes: 31487f8328f2 ("smp/cfd: Convert core to hotplug state machine") Signed-off-by: Lai Jiangshan Signed-off-by: Thomas Gleixner Cc: Peter Zijlstra Cc: Richard Weinberger Cc: Sebastian Andrzej Siewior Cc: Boris Ostrovsky Link: https://lkml.kernel.org/r/20171128131954.81229-1-jiangshanlai@gmail.com Signed-off-by: Greg Kroah-Hartman

cpu/hotplug: Reset node state after operation

2017-10-21T14:11:30Z

The recent rework of the cpu hotplug internals changed the usage of the per cpu state->node field, but missed to clean it up after usage. So subsequent hotplug operations use the stale pointer from a previous operation and hand it into the callback functions. The callbacks then dereference a pointer which either belongs to a different facility or points to freed and potentially reused memory. In either case data corruption and crashes are the obvious consequence. Reset the node and the last pointers in the per cpu state to NULL after the operation which set them has completed. Fixes: 96abb968549c ("smp/hotplug: Allow external multi-instance rollback") Reported-by: Tvrtko Ursulin Signed-off-by: Thomas Gleixner Cc: Peter Zijlstra Cc: Sebastian Andrzej Siewior Cc: Boris Ostrovsky Cc: "Paul E. McKenney" Link: https://lkml.kernel.org/r/alpine.DEB.2.20.1710211606130.3213@nanos

Merge branch 'core-watchdog-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2017-10-06T15:36:41Z

Pull watchddog clean-up and fixes from Thomas Gleixner: "The watchdog (hard/softlockup detector) code is pretty much broken in its current state. The patch series addresses this by removing all duct tape and refactoring it into a workable state. The reasons why I ask for inclusion that late in the cycle are: 1) The code causes lockdep splats vs. hotplug locking which get reported over and over. Unfortunately there is no easy fix. 2) The risk of breakage is minimal because it's already broken 3) As 4.14 is a long term stable kernel, I prefer to have working watchdog code in that and the lockdep issues resolved. I wouldn't ask you to pull if 4.14 wouldn't be a LTS kernel or if the solution would be easy to backport. 4) The series was around before the merge window opened, but then got delayed due to the UP failure caused by the for_each_cpu() surprise which we discussed recently. Changes vs. V1: - Addressed your review points - Addressed the warning in the powerpc code which was discovered late - Changed two function names which made sense up to a certain point in the series. Now they match what they do in the end. - Fixed a 'unused variable' warning, which got not detected by the intel robot. I triggered it when trying all possible related config combinations manually. Randconfig testing seems not random enough. The changes have been tested by and reviewed by Don Zickus and tested and acked by Micheal Ellerman for powerpc" * 'core-watchdog-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (36 commits) watchdog/core: Put softlockup_threads_initialized under ifdef guard watchdog/core: Rename some softlockup_* functions powerpc/watchdog: Make use of watchdog_nmi_probe() watchdog/core, powerpc: Lock cpus across reconfiguration watchdog/core, powerpc: Replace watchdog_nmi_reconfigure() watchdog/hardlockup/perf: Fix spelling mistake: "permanetely" -> "permanently" watchdog/hardlockup/perf: Cure UP damage watchdog/hardlockup: Clean up hotplug locking mess watchdog/hardlockup/perf: Simplify deferred event destroy watchdog/hardlockup/perf: Use new perf CPU enable mechanism watchdog/hardlockup/perf: Implement CPU enable replacement watchdog/hardlockup/perf: Implement init time detection of perf watchdog/hardlockup/perf: Implement init time perf validation watchdog/core: Get rid of the racy update loop watchdog/core, powerpc: Make watchdog_nmi_reconfigure() two stage watchdog/sysctl: Clean up sysctl variable name space watchdog/sysctl: Get rid of the #ifdeffery watchdog/core: Clean up header mess watchdog/core: Further simplify sysctl handling watchdog/core: Get rid of the thread teardown/setup dance ...

smp/hotplug: Hotplug state fail injection

2017-09-25T20:11:44Z

Add a sysfs file to one-time fail a specific state. This can be used to test the state rollback code paths. Something like this (hotplug-up.sh): #!/bin/bash echo 0 > /debug/sched_debug echo 1 > /debug/tracing/events/cpuhp/enable ALL_STATES=`cat /sys/devices/system/cpu/hotplug/states | cut -d':' -f1` STATES=${1:-$ALL_STATES} for state in $STATES do echo 0 > /sys/devices/system/cpu/cpu1/online echo 0 > /debug/tracing/trace echo Fail state: $state echo $state > /sys/devices/system/cpu/cpu1/hotplug/fail cat /sys/devices/system/cpu/cpu1/hotplug/fail echo 1 > /sys/devices/system/cpu/cpu1/online cat /debug/tracing/trace > hotfail-${state}.trace sleep 1 done Can be used to test for all possible rollback (barring multi-instance) scenarios on CPU-up, CPU-down is a trivial modification of the above. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Thomas Gleixner Cc: bigeasy@linutronix.de Cc: efault@gmx.de Cc: rostedt@goodmis.org Cc: max.byungchul.park@gmail.com Link: https://lkml.kernel.org/r/20170920170546.972581715@infradead.org

smp/hotplug: Differentiate the AP completion between up and down

2017-09-25T20:11:43Z

With lockdep-crossrelease we get deadlock reports that span cpu-up and cpu-down chains. Such deadlocks cannot possibly happen because cpu-up and cpu-down are globally serialized. takedown_cpu() irq_lock_sparse() wait_for_completion(&st->done) cpuhp_thread_fun cpuhp_up_callback cpuhp_invoke_callback irq_affinity_online_cpu irq_local_spare() irq_unlock_sparse() complete(&st->done) Now that we have consistent AP state, we can trivially separate the AP completion between up and down using st->bringup. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Thomas Gleixner Acked-by: max.byungchul.park@gmail.com Cc: bigeasy@linutronix.de Cc: efault@gmx.de Cc: rostedt@goodmis.org Link: https://lkml.kernel.org/r/20170920170546.872472799@infradead.org

smp/hotplug: Differentiate the AP-work lockdep class between up and down

2017-09-25T20:11:43Z

With lockdep-crossrelease we get deadlock reports that span cpu-up and cpu-down chains. Such deadlocks cannot possibly happen because cpu-up and cpu-down are globally serialized. CPU0 CPU1 CPU2 cpuhp_up_callbacks: takedown_cpu: cpuhp_thread_fun: cpuhp_state irq_lock_sparse() irq_lock_sparse() wait_for_completion() cpuhp_state complete() Now that we have consistent AP state, we can trivially separate the AP-work class between up and down using st->bringup. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Thomas Gleixner Cc: max.byungchul.park@gmail.com Cc: bigeasy@linutronix.de Cc: efault@gmx.de Cc: rostedt@goodmis.org Link: https://lkml.kernel.org/r/20170920170546.922524234@infradead.org

smp/hotplug: Callback vs state-machine consistency

2017-09-25T20:11:43Z

While the generic callback functions have an 'int' return and thus appear to be allowed to return error, this is not true for all states. Specifically, what used to be STARTING/DYING are ran with IRQs disabled from critical parts of CPU bringup/teardown and are not allowed to fail. Add WARNs to enforce this rule. But since some callbacks are indeed allowed to fail, we have the situation where a state-machine rollback encounters a failure, in this case we're stuck, we can't go forward and we can't go back. Also add a WARN for that case. AFAICT this is a fundamental 'problem' with no real obvious solution. We want the 'prepare' callbacks to allow failure on either up or down. Typically on prepare-up this would be things like -ENOMEM from resource allocations, and the typical usage in prepare-down would be something like -EBUSY to avoid CPUs being taken away. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Thomas Gleixner Cc: bigeasy@linutronix.de Cc: efault@gmx.de Cc: rostedt@goodmis.org Cc: max.byungchul.park@gmail.com Link: https://lkml.kernel.org/r/20170920170546.819539119@infradead.org

smp/hotplug: Rewrite AP state machine core

2017-09-25T20:11:42Z

There is currently no explicit state change on rollback. That is, st->bringup, st->rollback and st->target are not consistent when doing the rollback. Rework the AP state handling to be more coherent. This does mean we have to do a second AP kick-and-wait for rollback, but since rollback is the slow path of a slowpath, this really should not matter. Take this opportunity to simplify the AP thread function to only run a single callback per invocation. This unifies the three single/up/down modes is supports. The looping it used to do for up/down are achieved by retaining should_run and relying on the main smpboot_thread_fn() loop. (I have most of a patch that does the same for the BP state handling, but that's not critical and gets a little complicated because CPUHP_BRINGUP_CPU does the AP handoff from a callback, which gets recursive @st usage, I still have de-fugly that.) [ tglx: Move cpuhp_down_callbacks() et al. into the HOTPLUG_CPU section to avoid gcc complaining about unused functions. Make the HOTPLUG_CPU one piece instead of having two consecutive ifdef sections of the same type. ] Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Thomas Gleixner Cc: bigeasy@linutronix.de Cc: efault@gmx.de Cc: rostedt@goodmis.org Cc: max.byungchul.park@gmail.com Link: https://lkml.kernel.org/r/20170920170546.769658088@infradead.org

smp/hotplug: Allow external multi-instance rollback

2017-09-25T20:11:42Z

Currently the rollback of multi-instance states is handled inside cpuhp_invoke_callback(). The problem is that when we want to allow an explicit state change for rollback, we need to return from the function without doing the rollback. Change cpuhp_invoke_callback() to optionally return the multi-instance state, such that rollback can be done from a subsequent call. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Thomas Gleixner Cc: bigeasy@linutronix.de Cc: efault@gmx.de Cc: rostedt@goodmis.org Cc: max.byungchul.park@gmail.com Link: https://lkml.kernel.org/r/20170920170546.720361181@infradead.org