linux/kernel/cpu.c, branch v4.18

init: rename and re-order boot_cpu_state_init()

2018-08-12T19:19:42Z

This is purely a preparatory patch for upcoming changes during the 4.19 merge window. We have a function called "boot_cpu_state_init()" that isn't really about the bootup cpu state: that is done much earlier by the similarly named "boot_cpu_init()" (note lack of "state" in name). This function initializes some hotplug CPU state, and needs to run after the percpu data has been properly initialized. It even has a comment to that effect. Except it _doesn't_ actually run after the percpu data has been properly initialized. On x86 it happens to do that, but on at least arm and arm64, the percpu base pointers are initialized by the arch-specific 'smp_prepare_boot_cpu()' hook, which ran _after_ boot_cpu_state_init(). This had some unexpected results, and in particular we have a patch pending for the merge window that did the obvious cleanup of using 'this_cpu_write()' in the cpu hotplug init code: - per_cpu_ptr(&cpuhp_state, smp_processor_id())->state = CPUHP_ONLINE; + this_cpu_write(cpuhp_state.state, CPUHP_ONLINE); which is obviously the right thing to do. Except because of the ordering issue, it actually failed miserably and unexpectedly on arm64. So this just fixes the ordering, and changes the name of the function to be 'boot_cpu_hotplug_init()' to make it obvious that it's about cpu hotplug state, because the core CPU state was supposed to have already been done earlier. Marked for stable, since the (not yet merged) patch that will show this problem is marked for stable. Reported-by: Vlastimil Babka Reported-by: Mian Yousaf Kaukab Suggested-by: Catalin Marinas Acked-by: Thomas Gleixner Cc: Will Deacon Cc: stable@kernel.org Signed-off-by: Linus Torvalds

cpu/hotplug: Fix unused function warning

2018-03-15T19:34:40Z

The cpuhp_is_ap_state() function is no longer called outside of the CONFIG_SMP #ifdef section, causing a harmless warning: kernel/cpu.c:129:13: error: 'cpuhp_is_ap_state' defined but not used [-Werror=unused-function] This moves the function into the #ifdef to get a clean build again. Fixes: 17a2f1ced028 ("cpu/hotplug: Merge cpuhp_bp_states and cpuhp_ap_states") Signed-off-by: Arnd Bergmann Signed-off-by: Thomas Gleixner Cc: Peter Zijlstra Cc: Sebastian Andrzej Siewior Cc: Lai Jiangshan Cc: "Paul E. McKenney" Link: https://lkml.kernel.org/r/20180315153829.3819606-1-arnd@arndb.de

cpu/hotplug: Merge cpuhp_bp_states and cpuhp_ap_states

2018-03-14T15:38:43Z

cpuhp_bp_states and cpuhp_ap_states have different set of steps without any conflicting steps, so that they can be merged. The original `[CPUHP_BRINGUP_CPU] = { },` is removed, because the new cpuhp_hp_states has CPUHP_ONLINE index which is larger than CPUHP_BRINGUP_CPU. Signed-off-by: Lai Jiangshan 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/20171201135008.21633-1-jiangshanlai@gmail.com

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

2017-12-31T20:30:34Z

Pull timer fixes from Thomas Gleixner: "A pile of fixes for long standing issues with the timer wheel and the NOHZ code: - Prevent timer base confusion accross the nohz switch, which can cause unlocked access and data corruption - Reinitialize the stale base clock on cpu hotplug to prevent subtle side effects including rollovers on 32bit - Prevent an interrupt storm when the timer softirq is already pending caused by tick_nohz_stop_sched_tick() - Move the timer start tracepoint to a place where it actually makes sense - Add documentation to timerqueue functions as they caused confusion several times now" * 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: timerqueue: Document return values of timerqueue_add/del() timers: Invoke timer_start_debug() where it makes sense nohz: Prevent a timer interrupt storm in tick_nohz_stop_sched_tick() timers: Reinitialize per cpu bases on hotplug timers: Use deferrable base independent of base::nohz_active

timers: Reinitialize per cpu bases on hotplug

2017-12-29T22:13:09Z

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 Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/alpine.DEB.2.20.1712272152200.2431@nanos

cpu/hotplug: Move inline keyword at the beginning of declaration

2017-12-27T18:41:04Z

Fix non-fatal warnings such as: kernel/cpu.c:95:1: warning: ‘inline’ is not at beginning of declaration [-Wold-style-declaration] static void inline cpuhp_lock_release(bool bringup) { } ^~~~~~ Signed-off-by: Mathieu Malaterre Signed-off-by: Thomas Gleixner Cc: Arnd Bergmann Cc: Sebastian Andrzej Siewior Cc: Peter Zijlstra Cc: "Paul E. McKenney" Link: https://lkml.kernel.org/r/20171226140855.16583-1-malat@debian.org

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

2017-12-07T01:45:36Z

Pull CPU hotplug fix from Ingo Molnar: "A single fix moving the smp-call queue flush step to the intended point in the state machine" * 'smp-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: smp/hotplug: Move step CPUHP_AP_SMPCFD_DYING to the correct place

cpu/hotplug: Fix state name in takedown_cpu() comment

2017-12-06T18:28:45Z

CPUHP_AP_SCHED_MIGRATE_DYING doesn't exist, it looks like this was supposed to refer to CPUHP_AP_SCHED_STARTING's teardown callback, i.e. sched_cpu_dying(). Signed-off-by: Brendan Jackman Cc: Boris Ostrovsky Cc: Dietmar Eggemann Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Quentin Perret Cc: Sebastian Andrzej Siewior Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/20171206105911.28093-1-brendan.jackman@arm.com Signed-off-by: Ingo Molnar

smp/hotplug: Move step CPUHP_AP_SMPCFD_DYING to the correct place

2017-11-28T13:40:23Z

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: stable@vger.kernel.org Cc: Boris Ostrovsky Link: https://lkml.kernel.org/r/20171128131954.81229-1-jiangshanlai@gmail.com

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