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

Pull cpu hotplug updates from Thomas Gleixner:
 "This is the first part of the ongoing cpu hotplug rework:

   - Initial implementation of the state machine

   - Runs all online and prepare down callbacks on the plugged cpu and
     not on some random processor

   - Replaces busy loop waiting with completions

   - Adds tracepoints so the states can be followed"

More detailed commentary on this work from an earlier email:
 "What's wrong with the current cpu hotplug infrastructure?

   - Asymmetry

     The hotplug notifier mechanism is asymmetric versus the bringup and
     teardown.  This is mostly caused by the notifier mechanism.

   - Largely undocumented dependencies

     While some notifiers use explicitely defined notifier priorities,
     we have quite some notifiers which use numerical priorities to
     express dependencies without any documentation why.

   - Control processor driven

     Most of the bringup/teardown of a cpu is driven by a control
     processor.  While it is understandable, that preperatory steps,
     like idle thread creation, memory allocation for and initialization
     of essential facilities needs to be done before a cpu can boot,
     there is no reason why everything else must run on a control
     processor.  Before this patch series, bringup looks like this:

       Control CPU                     Booting CPU

       do preparatory steps
       kick cpu into life

                                       do low level init

       sync with booting cpu           sync with control cpu

       bring the rest up

   - All or nothing approach

     There is no way to do partial bringups.  That's something which is
     really desired because we waste e.g.  at boot substantial amount of
     time just busy waiting that the cpu comes to life.  That's stupid
     as we could very well do preparatory steps and the initial IPI for
     other cpus and then go back and do the necessary low level
     synchronization with the freshly booted cpu.

   - Minimal debuggability

     Due to the notifier based design, it's impossible to switch between
     two stages of the bringup/teardown back and forth in order to test
     the correctness.  So in many hotplug notifiers the cancel
     mechanisms are either not existant or completely untested.

   - Notifier [un]registering is tedious

     To [un]register notifiers we need to protect against hotplug at
     every callsite.  There is no mechanism that bringup/teardown
     callbacks are issued on the online cpus, so every caller needs to
     do it itself.  That also includes error rollback.

  What's the new design?

     The base of the new design is a symmetric state machine, where both
     the control processor and the booting/dying cpu execute a well
     defined set of states.  Each state is symmetric in the end, except
     for some well defined exceptions, and the bringup/teardown can be
     stopped and reversed at almost all states.

     So the bringup of a cpu will look like this in the future:

       Control CPU                     Booting CPU

       do preparatory steps
       kick cpu into life

                                       do low level init

       sync with booting cpu           sync with control cpu

                                       bring itself up

     The synchronization step does not require the control cpu to wait.
     That mechanism can be done asynchronously via a worker or some
     other mechanism.

     The teardown can be made very similar, so that the dying cpu cleans
     up and brings itself down.  Cleanups which need to be done after
     the cpu is gone, can be scheduled asynchronously as well.

  There is a long way to this, as we need to refactor the notion when a
  cpu is available.  Today we set the cpu online right after it comes
  out of the low level bringup, which is not really correct.

  The proper mechanism is to set it to available, i.e. cpu local
  threads, like softirqd, hotplug thread etc. can be scheduled on that
  cpu, and once it finished all booting steps, it's set to online, so
  general workloads can be scheduled on it.  The reverse happens on
  teardown.  First thing to do is to forbid scheduling of general
  workloads, then teardown all the per cpu resources and finally shut it
  off completely.

  This patch series implements the basic infrastructure for this at the
  core level.  This includes the following:

   - Basic state machine implementation with well defined states, so
     ordering and prioritization can be expressed.

   - Interfaces to [un]register state callbacks

     This invokes the bringup/teardown callback on all online cpus with
     the proper protection in place and [un]installs the callbacks in
     the state machine array.

     For callbacks which have no particular ordering requirement we have
     a dynamic state space, so that drivers don't have to register an
     explicit hotplug state.

     If a callback fails, the code automatically does a rollback to the
     previous state.

   - Sysfs interface to drive the state machine to a particular step.

     This is only partially functional today.  Full functionality and
     therefor testability will be achieved once we converted all
     existing hotplug notifiers over to the new scheme.

   - Run all CPU_ONLINE/DOWN_PREPARE notifiers on the booting/dying
     processor:

       Control CPU                     Booting CPU

       do preparatory steps
       kick cpu into life

                                       do low level init

       sync with booting cpu           sync with control cpu
       wait for boot
                                       bring itself up

                                       Signal completion to control cpu

     In a previous step of this work we've done a full tree mechanical
     conversion of all hotplug notifiers to the new scheme.  The balance
     is a net removal of about 4000 lines of code.

     This is not included in this series, as we decided to take a
     different approach.  Instead of mechanically converting everything
     over, we will do a proper overhaul of the usage sites one by one so
     they nicely fit into the symmetric callback scheme.

     I decided to do that after I looked at the ugliness of some of the
     converted sites and figured out that their hotplug mechanism is
     completely buggered anyway.  So there is no point to do a
     mechanical conversion first as we need to go through the usage
     sites one by one again in order to achieve a full symmetric and
     testable behaviour"

* 'smp-hotplug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (23 commits)
  cpu/hotplug: Document states better
  cpu/hotplug: Fix smpboot thread ordering
  cpu/hotplug: Remove redundant state check
  cpu/hotplug: Plug death reporting race
  rcu: Make CPU_DYING_IDLE an explicit call
  cpu/hotplug: Make wait for dead cpu completion based
  cpu/hotplug: Let upcoming cpu bring itself fully up
  arch/hotplug: Call into idle with a proper state
  cpu/hotplug: Move online calls to hotplugged cpu
  cpu/hotplug: Create hotplug threads
  cpu/hotplug: Split out the state walk into functions
  cpu/hotplug: Unpark smpboot threads from the state machine
  cpu/hotplug: Move scheduler cpu_online notifier to hotplug core
  cpu/hotplug: Implement setup/removal interface
  cpu/hotplug: Make target state writeable
  cpu/hotplug: Add sysfs state interface
  cpu/hotplug: Hand in target state to _cpu_up/down
  cpu/hotplug: Convert the hotplugged cpu work to a state machine
  cpu/hotplug: Convert to a state machine for the control processor
  cpu/hotplug: Add tracepoints
  ...

21 files changed, 21 insertions, 21 deletions

diff --git a/arch/alpha/kernel/smp.c b/arch/alpha/kernel/smp.c
index 2f24447fef92..46bf263c3153 100644
--- a/arch/alpha/kernel/smp.c
+++ b/arch/alpha/kernel/smp.c
@@ -168,7 +168,7 @@ smp_callin(void)
 	      cpuid, current, current->active_mm));
 
 	preempt_disable();
-	cpu_startup_entry(CPUHP_ONLINE);
+	cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
 }
 
 /* Wait until hwrpb->txrdy is clear for cpu.  Return -1 on timeout.  */
diff --git a/arch/arc/kernel/smp.c b/arch/arc/kernel/smp.c
index 424e937da5c8..4cb3add77c75 100644
--- a/arch/arc/kernel/smp.c
+++ b/arch/arc/kernel/smp.c
@@ -142,7 +142,7 @@ void start_kernel_secondary(void)
 
 	local_irq_enable();
 	preempt_disable();
-	cpu_startup_entry(CPUHP_ONLINE);
+	cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
 }
 
 /*
diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
index 37312f6749f3..baee70267f29 100644
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -409,7 +409,7 @@ asmlinkage void secondary_start_kernel(void)
 	/*
 	 * OK, it's off to the idle thread for us
 	 */
-	cpu_startup_entry(CPUHP_ONLINE);
+	cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
 }
 
 void __init smp_cpus_done(unsigned int max_cpus)
diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index b1adc51b2c2e..460765799c64 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -195,7 +195,7 @@ asmlinkage void secondary_start_kernel(void)
 	/*
 	 * OK, it's off to the idle thread for us
 	 */
-	cpu_startup_entry(CPUHP_ONLINE);
+	cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
 }
 
 #ifdef CONFIG_HOTPLUG_CPU
diff --git a/arch/blackfin/mach-common/smp.c b/arch/blackfin/mach-common/smp.c
index 0030e21cfceb..23c4ef5f8bdc 100644
--- a/arch/blackfin/mach-common/smp.c
+++ b/arch/blackfin/mach-common/smp.c
@@ -333,7 +333,7 @@ void secondary_start_kernel(void)
 
 	/* We are done with local CPU inits, unblock the boot CPU. */
 	set_cpu_online(cpu, true);
-	cpu_startup_entry(CPUHP_ONLINE);
+	cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
 }
 
 void __init smp_prepare_boot_cpu(void)
diff --git a/arch/hexagon/kernel/smp.c b/arch/hexagon/kernel/smp.c
index ff759f26b96a..983bae7d2665 100644
--- a/arch/hexagon/kernel/smp.c
+++ b/arch/hexagon/kernel/smp.c
@@ -180,7 +180,7 @@ void start_secondary(void)
 
 	local_irq_enable();
 
-	cpu_startup_entry(CPUHP_ONLINE);
+	cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
 }
 
 
diff --git a/arch/ia64/kernel/smpboot.c b/arch/ia64/kernel/smpboot.c
index 0e76fad27975..74fe317477e6 100644
--- a/arch/ia64/kernel/smpboot.c
+++ b/arch/ia64/kernel/smpboot.c
@@ -454,7 +454,7 @@ start_secondary (void *unused)
 	preempt_disable();
 	smp_callin();
 
-	cpu_startup_entry(CPUHP_ONLINE);
+	cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
 	return 0;
 }
 
diff --git a/arch/m32r/kernel/smpboot.c b/arch/m32r/kernel/smpboot.c
index a468467542f4..f98d2f6519d6 100644
--- a/arch/m32r/kernel/smpboot.c
+++ b/arch/m32r/kernel/smpboot.c
@@ -432,7 +432,7 @@ int __init start_secondary(void *unused)
 	 */
 	local_flush_tlb_all();
 
-	cpu_startup_entry(CPUHP_ONLINE);
+	cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
 	return 0;
 }
 
diff --git a/arch/metag/kernel/smp.c b/arch/metag/kernel/smp.c
index c3c6f0864881..bad13232de51 100644
--- a/arch/metag/kernel/smp.c
+++ b/arch/metag/kernel/smp.c
@@ -396,7 +396,7 @@ asmlinkage void secondary_start_kernel(void)
 	/*
 	 * OK, it's off to the idle thread for us
 	 */
-	cpu_startup_entry(CPUHP_ONLINE);
+	cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
 }
 
 void __init smp_cpus_done(unsigned int max_cpus)
diff --git a/arch/mips/kernel/smp.c b/arch/mips/kernel/smp.c
index 8b687fee0cb0..37708d9af638 100644
--- a/arch/mips/kernel/smp.c
+++ b/arch/mips/kernel/smp.c
@@ -328,7 +328,7 @@ asmlinkage void start_secondary(void)
 	WARN_ON_ONCE(!irqs_disabled());
 	mp_ops->smp_finish();
 
-	cpu_startup_entry(CPUHP_ONLINE);
+	cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
 }
 
 static void stop_this_cpu(void *dummy)
diff --git a/arch/mn10300/kernel/smp.c b/arch/mn10300/kernel/smp.c
index f984193718b1..426173c4b0b9 100644
--- a/arch/mn10300/kernel/smp.c
+++ b/arch/mn10300/kernel/smp.c
@@ -675,7 +675,7 @@ int __init start_secondary(void *unused)
 #ifdef CONFIG_GENERIC_CLOCKEVENTS
 	init_clockevents();
 #endif
-	cpu_startup_entry(CPUHP_ONLINE);
+	cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
 	return 0;
 }
 
diff --git a/arch/parisc/kernel/smp.c b/arch/parisc/kernel/smp.c
index 52e85973a283..c2a9cc55a62f 100644
--- a/arch/parisc/kernel/smp.c
+++ b/arch/parisc/kernel/smp.c
@@ -305,7 +305,7 @@ void __init smp_callin(void)
 
 	local_irq_enable();  /* Interrupts have been off until now */
 
-	cpu_startup_entry(CPUHP_ONLINE);
+	cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
 
 	/* NOTREACHED */
 	panic("smp_callin() AAAAaaaaahhhh....\n");
diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index ec9ec2058d2d..cc13d4c83291 100644
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -727,7 +727,7 @@ void start_secondary(void *unused)
 
 	local_irq_enable();
 
-	cpu_startup_entry(CPUHP_ONLINE);
+	cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
 
 	BUG();
 }
diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index 3c65a8eae34d..40a6b4f9c36c 100644
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -798,7 +798,7 @@ static void smp_start_secondary(void *cpuvoid)
 	set_cpu_online(smp_processor_id(), true);
 	inc_irq_stat(CPU_RST);
 	local_irq_enable();
-	cpu_startup_entry(CPUHP_ONLINE);
+	cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
 }
 
 /* Upping and downing of CPUs */
diff --git a/arch/sh/kernel/smp.c b/arch/sh/kernel/smp.c
index de6be008fc01..13f633add29a 100644
--- a/arch/sh/kernel/smp.c
+++ b/arch/sh/kernel/smp.c
@@ -203,7 +203,7 @@ asmlinkage void start_secondary(void)
 	set_cpu_online(cpu, true);
 	per_cpu(cpu_state, cpu) = CPU_ONLINE;
 
-	cpu_startup_entry(CPUHP_ONLINE);
+	cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
 }
 
 extern struct {
diff --git a/arch/sparc/kernel/smp_32.c b/arch/sparc/kernel/smp_32.c
index b3a5d81b20f0..fb30e7c6a5b1 100644
--- a/arch/sparc/kernel/smp_32.c
+++ b/arch/sparc/kernel/smp_32.c
@@ -364,7 +364,7 @@ static void sparc_start_secondary(void *arg)
 	local_irq_enable();
 
 	wmb();
-	cpu_startup_entry(CPUHP_ONLINE);
+	cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
 
 	/* We should never reach here! */
 	BUG();
diff --git a/arch/sparc/kernel/smp_64.c b/arch/sparc/kernel/smp_64.c
index 19cd08d18672..8a6151a628ce 100644
--- a/arch/sparc/kernel/smp_64.c
+++ b/arch/sparc/kernel/smp_64.c
@@ -134,7 +134,7 @@ void smp_callin(void)
 
 	local_irq_enable();
 
-	cpu_startup_entry(CPUHP_ONLINE);
+	cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
 }
 
 void cpu_panic(void)
diff --git a/arch/tile/kernel/smpboot.c b/arch/tile/kernel/smpboot.c
index 20d52a98e171..6c0abaacec33 100644
--- a/arch/tile/kernel/smpboot.c
+++ b/arch/tile/kernel/smpboot.c
@@ -208,7 +208,7 @@ void online_secondary(void)
 	/* Set up tile-timer clock-event device on this cpu */
 	setup_tile_timer();
 
-	cpu_startup_entry(CPUHP_ONLINE);
+	cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
 }
 
 int __cpu_up(unsigned int cpu, struct task_struct *tidle)
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 3bf1e0b5f827..643dbdccf4bc 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -256,7 +256,7 @@ static void notrace start_secondary(void *unused)
 	x86_cpuinit.setup_percpu_clockev();
 
 	wmb();
-	cpu_startup_entry(CPUHP_ONLINE);
+	cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
 }
 
 int topology_update_package_map(unsigned int apicid, unsigned int cpu)
diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
index 3f4ebf0261f2..3c6d17fd423a 100644
--- a/arch/x86/xen/smp.c
+++ b/arch/x86/xen/smp.c
@@ -112,7 +112,7 @@ asmlinkage __visible void cpu_bringup_and_idle(int cpu)
 		xen_pvh_secondary_vcpu_init(cpu);
 #endif
 	cpu_bringup();
-	cpu_startup_entry(CPUHP_ONLINE);
+	cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
 }
 
 static void xen_smp_intr_free(unsigned int cpu)
diff --git a/arch/xtensa/kernel/smp.c b/arch/xtensa/kernel/smp.c
index 4d02e38514f5..fc4ad21a5ed4 100644
--- a/arch/xtensa/kernel/smp.c
+++ b/arch/xtensa/kernel/smp.c
@@ -157,7 +157,7 @@ void secondary_start_kernel(void)
 
 	complete(&cpu_running);
 
-	cpu_startup_entry(CPUHP_ONLINE);
+	cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
 }
 
 static void mx_cpu_start(void *p)