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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * Context tracking: Probe on high level context boundaries such as kernel,
  * userspace, guest or idle.
  *
  * This is used by RCU to remove its dependency on the timer tick while a CPU
  * runs in idle, userspace or guest mode.
  *
  * User/guest tracking started by Frederic Weisbecker:
  *
  * Copyright (C) 2012 Red Hat, Inc., Frederic Weisbecker
  *
  * Many thanks to Gilad Ben-Yossef, Paul McKenney, Ingo Molnar, Andrew Morton,
  * Steven Rostedt, Peter Zijlstra for suggestions and improvements.
  *
  * RCU extended quiescent state bits imported from kernel/rcu/tree.c
  * where the relevant authorship may be found.
  */
 
 #include <linux/context_tracking.h>
 #include <linux/rcupdate.h>
 #include <linux/sched.h>
 #include <linux/hardirq.h>
 #include <linux/export.h>
 #include <linux/kprobes.h>
 #include <trace/events/rcu.h>
 
 
 DEFINE_PER_CPU(struct context_tracking, context_tracking) = {
 #ifdef CONFIG_CONTEXT_TRACKING_IDLE
     .dynticks_nesting = 1,
     .dynticks_nmi_nesting = DYNTICK_IRQ_NONIDLE,
 #endif
     .state = ATOMIC_INIT(RCU_DYNTICKS_IDX),
 };
 EXPORT_SYMBOL_GPL(context_tracking);
 
 #ifdef CONFIG_CONTEXT_TRACKING_IDLE
 #define TPS(x)  tracepoint_string(x)
 
 /* Record the current task on dyntick-idle entry. */
 static __always_inline void rcu_dynticks_task_enter(void)
 {
 #if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL)
     WRITE_ONCE(current->rcu_tasks_idle_cpu, smp_processor_id());
 #endif /* #if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL) */
 }
 
 /* Record no current task on dyntick-idle exit. */
 static __always_inline void rcu_dynticks_task_exit(void)
 {
 #if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL)
     WRITE_ONCE(current->rcu_tasks_idle_cpu, -1);
 #endif /* #if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL) */
 }
 
 /* Turn on heavyweight RCU tasks trace readers on idle/user entry. */
 static __always_inline void rcu_dynticks_task_trace_enter(void)
 {
 #ifdef CONFIG_TASKS_TRACE_RCU
     if (IS_ENABLED(CONFIG_TASKS_TRACE_RCU_READ_MB))
         current->trc_reader_special.b.need_mb = true;
 #endif /* #ifdef CONFIG_TASKS_TRACE_RCU */
 }
 
 /* Turn off heavyweight RCU tasks trace readers on idle/user exit. */
 static __always_inline void rcu_dynticks_task_trace_exit(void)
 {
 #ifdef CONFIG_TASKS_TRACE_RCU
     if (IS_ENABLED(CONFIG_TASKS_TRACE_RCU_READ_MB))
         current->trc_reader_special.b.need_mb = false;
 #endif /* #ifdef CONFIG_TASKS_TRACE_RCU */
 }
 
 /*
  * Record entry into an extended quiescent state.  This is only to be
  * called when not already in an extended quiescent state, that is,
  * RCU is watching prior to the call to this function and is no longer
  * watching upon return.
  */
 static noinstr void ct_kernel_exit_state(int offset)
 {
     int seq;
 
     /*
      * CPUs seeing atomic_add_return() must see prior RCU read-side
      * critical sections, and we also must force ordering with the
      * next idle sojourn.
      */
     rcu_dynticks_task_trace_enter();  // Before ->dynticks update!
     seq = ct_state_inc(offset);
     // RCU is no longer watching.  Better be in extended quiescent state!
     WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && (seq & RCU_DYNTICKS_IDX));
 }
 
 /*
  * Record exit from an extended quiescent state.  This is only to be
  * called from an extended quiescent state, that is, RCU is not watching
  * prior to the call to this function and is watching upon return.
  */
 static noinstr void ct_kernel_enter_state(int offset)
 {
     int seq;
 
     /*
      * CPUs seeing atomic_add_return() must see prior idle sojourns,
      * and we also must force ordering with the next RCU read-side
      * critical section.
      */
     seq = ct_state_inc(offset);
     // RCU is now watching.  Better not be in an extended quiescent state!
     rcu_dynticks_task_trace_exit();  // After ->dynticks update!
     WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !(seq & RCU_DYNTICKS_IDX));
 }
 
 /*
  * Enter an RCU extended quiescent state, which can be either the
  * idle loop or adaptive-tickless usermode execution.
  *
  * We crowbar the ->dynticks_nmi_nesting field to zero to allow for
  * the possibility of usermode upcalls having messed up our count
  * of interrupt nesting level during the prior busy period.
  */
 static void noinstr ct_kernel_exit(bool user, int offset)
 {
     struct context_tracking *ct = this_cpu_ptr(&context_tracking);
 
     WARN_ON_ONCE(ct_dynticks_nmi_nesting() != DYNTICK_IRQ_NONIDLE);
     WRITE_ONCE(ct->dynticks_nmi_nesting, 0);
     WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) &&
              ct_dynticks_nesting() == 0);
     if (ct_dynticks_nesting() != 1) {
         // RCU will still be watching, so just do accounting and leave.
         ct->dynticks_nesting--;
         return;
     }
 
     instrumentation_begin();
     lockdep_assert_irqs_disabled();
     trace_rcu_dyntick(TPS("Start"), ct_dynticks_nesting(), 0, ct_dynticks());
     WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && !is_idle_task(current));
     rcu_preempt_deferred_qs(current);
 
     // instrumentation for the noinstr ct_kernel_exit_state()
     instrument_atomic_write(&ct->state, sizeof(ct->state));
 
     instrumentation_end();
     WRITE_ONCE(ct->dynticks_nesting, 0); /* Avoid irq-access tearing. */
     // RCU is watching here ...
     ct_kernel_exit_state(offset);
     // ... but is no longer watching here.
     rcu_dynticks_task_enter();
 }
 
 /*
  * Exit an RCU extended quiescent state, which can be either the
  * idle loop or adaptive-tickless usermode execution.
  *
  * We crowbar the ->dynticks_nmi_nesting field to DYNTICK_IRQ_NONIDLE to
  * allow for the possibility of usermode upcalls messing up our count of
  * interrupt nesting level during the busy period that is just now starting.
  */
 static void noinstr ct_kernel_enter(bool user, int offset)
 {
     struct context_tracking *ct = this_cpu_ptr(&context_tracking);
     long oldval;
 
     WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !raw_irqs_disabled());
     oldval = ct_dynticks_nesting();
     WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && oldval < 0);
     if (oldval) {
         // RCU was already watching, so just do accounting and leave.
         ct->dynticks_nesting++;
         return;
     }
     rcu_dynticks_task_exit();
     // RCU is not watching here ...
     ct_kernel_enter_state(offset);
     // ... but is watching here.
     instrumentation_begin();
 
     // instrumentation for the noinstr ct_kernel_enter_state()
     instrument_atomic_write(&ct->state, sizeof(ct->state));
 
     trace_rcu_dyntick(TPS("End"), ct_dynticks_nesting(), 1, ct_dynticks());
     WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && !is_idle_task(current));
     WRITE_ONCE(ct->dynticks_nesting, 1);
     WARN_ON_ONCE(ct_dynticks_nmi_nesting());
     WRITE_ONCE(ct->dynticks_nmi_nesting, DYNTICK_IRQ_NONIDLE);
     instrumentation_end();
 }
 
 /**
  * ct_nmi_exit - inform RCU of exit from NMI context
  *
  * If we are returning from the outermost NMI handler that interrupted an
  * RCU-idle period, update ct->state and ct->dynticks_nmi_nesting
  * to let the RCU grace-period handling know that the CPU is back to
  * being RCU-idle.
  *
  * If you add or remove a call to ct_nmi_exit(), be sure to test
  * with CONFIG_RCU_EQS_DEBUG=y.
  */
 void noinstr ct_nmi_exit(void)
 {
     struct context_tracking *ct = this_cpu_ptr(&context_tracking);
 
     instrumentation_begin();
     /*
      * Check for ->dynticks_nmi_nesting underflow and bad ->dynticks.
      * (We are exiting an NMI handler, so RCU better be paying attention
      * to us!)
      */
     WARN_ON_ONCE(ct_dynticks_nmi_nesting() <= 0);
     WARN_ON_ONCE(rcu_dynticks_curr_cpu_in_eqs());
 
     /*
      * If the nesting level is not 1, the CPU wasn't RCU-idle, so
      * leave it in non-RCU-idle state.
      */
     if (ct_dynticks_nmi_nesting() != 1) {
         trace_rcu_dyntick(TPS("--="), ct_dynticks_nmi_nesting(), ct_dynticks_nmi_nesting() - 2,
                   ct_dynticks());
         WRITE_ONCE(ct->dynticks_nmi_nesting, /* No store tearing. */
                ct_dynticks_nmi_nesting() - 2);
         instrumentation_end();
         return;
     }
 
     /* This NMI interrupted an RCU-idle CPU, restore RCU-idleness. */
     trace_rcu_dyntick(TPS("Startirq"), ct_dynticks_nmi_nesting(), 0, ct_dynticks());
     WRITE_ONCE(ct->dynticks_nmi_nesting, 0); /* Avoid store tearing. */
 
     // instrumentation for the noinstr ct_kernel_exit_state()
     instrument_atomic_write(&ct->state, sizeof(ct->state));
     instrumentation_end();
 
     // RCU is watching here ...
     ct_kernel_exit_state(RCU_DYNTICKS_IDX);
     // ... but is no longer watching here.
 
     if (!in_nmi())
         rcu_dynticks_task_enter();
 }
 
 /**
  * ct_nmi_enter - inform RCU of entry to NMI context
  *
  * If the CPU was idle from RCU's viewpoint, update ct->state and
  * ct->dynticks_nmi_nesting to let the RCU grace-period handling know
  * that the CPU is active.  This implementation permits nested NMIs, as
  * long as the nesting level does not overflow an int.  (You will probably
  * run out of stack space first.)
  *
  * If you add or remove a call to ct_nmi_enter(), be sure to test
  * with CONFIG_RCU_EQS_DEBUG=y.
  */
 void noinstr ct_nmi_enter(void)
 {
     long incby = 2;
     struct context_tracking *ct = this_cpu_ptr(&context_tracking);
 
     /* Complain about underflow. */
     WARN_ON_ONCE(ct_dynticks_nmi_nesting() < 0);
 
     /*
      * If idle from RCU viewpoint, atomically increment ->dynticks
      * to mark non-idle and increment ->dynticks_nmi_nesting by one.
      * Otherwise, increment ->dynticks_nmi_nesting by two.  This means
      * if ->dynticks_nmi_nesting is equal to one, we are guaranteed
      * to be in the outermost NMI handler that interrupted an RCU-idle
      * period (observation due to Andy Lutomirski).
      */
     if (rcu_dynticks_curr_cpu_in_eqs()) {
 
         if (!in_nmi())
             rcu_dynticks_task_exit();
 
         // RCU is not watching here ...
         ct_kernel_enter_state(RCU_DYNTICKS_IDX);
         // ... but is watching here.
 
         instrumentation_begin();
         // instrumentation for the noinstr rcu_dynticks_curr_cpu_in_eqs()
         instrument_atomic_read(&ct->state, sizeof(ct->state));
         // instrumentation for the noinstr ct_kernel_enter_state()
         instrument_atomic_write(&ct->state, sizeof(ct->state));
 
         incby = 1;
     } else if (!in_nmi()) {
         instrumentation_begin();
         rcu_irq_enter_check_tick();
     } else  {
         instrumentation_begin();
     }
 
     trace_rcu_dyntick(incby == 1 ? TPS("Endirq") : TPS("++="),
               ct_dynticks_nmi_nesting(),
               ct_dynticks_nmi_nesting() + incby, ct_dynticks());
     instrumentation_end();
     WRITE_ONCE(ct->dynticks_nmi_nesting, /* Prevent store tearing. */
            ct_dynticks_nmi_nesting() + incby);
     barrier();
 }
 
 /**
  * ct_idle_enter - inform RCU that current CPU is entering idle
  *
  * Enter idle mode, in other words, -leave- the mode in which RCU
  * read-side critical sections can occur.  (Though RCU read-side
  * critical sections can occur in irq handlers in idle, a possibility
  * handled by irq_enter() and irq_exit().)
  *
  * If you add or remove a call to ct_idle_enter(), be sure to test with
  * CONFIG_RCU_EQS_DEBUG=y.
  */
 void noinstr ct_idle_enter(void)
 {
     WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !raw_irqs_disabled());
     ct_kernel_exit(false, RCU_DYNTICKS_IDX + CONTEXT_IDLE);
 }
 EXPORT_SYMBOL_GPL(ct_idle_enter);
 
 /**
  * ct_idle_exit - inform RCU that current CPU is leaving idle
  *
  * Exit idle mode, in other words, -enter- the mode in which RCU
  * read-side critical sections can occur.
  *
  * If you add or remove a call to ct_idle_exit(), be sure to test with
  * CONFIG_RCU_EQS_DEBUG=y.
  */
 void noinstr ct_idle_exit(void)
 {
     unsigned long flags;
 
     raw_local_irq_save(flags);
     ct_kernel_enter(false, RCU_DYNTICKS_IDX - CONTEXT_IDLE);
     raw_local_irq_restore(flags);
 }
 EXPORT_SYMBOL_GPL(ct_idle_exit);
 
 /**
  * ct_irq_enter - inform RCU that current CPU is entering irq away from idle
  *
  * Enter an interrupt handler, which might possibly result in exiting
  * idle mode, in other words, entering the mode in which read-side critical
  * sections can occur.  The caller must have disabled interrupts.
  *
  * Note that the Linux kernel is fully capable of entering an interrupt
  * handler that it never exits, for example when doing upcalls to user mode!
  * This code assumes that the idle loop never does upcalls to user mode.
  * If your architecture's idle loop does do upcalls to user mode (or does
  * anything else that results in unbalanced calls to the irq_enter() and
  * irq_exit() functions), RCU will give you what you deserve, good and hard.
  * But very infrequently and irreproducibly.
  *
  * Use things like work queues to work around this limitation.
  *
  * You have been warned.
  *
  * If you add or remove a call to ct_irq_enter(), be sure to test with
  * CONFIG_RCU_EQS_DEBUG=y.
  */
 noinstr void ct_irq_enter(void)
 {
     lockdep_assert_irqs_disabled();
     ct_nmi_enter();
 }
 
 /**
  * ct_irq_exit - inform RCU that current CPU is exiting irq towards idle
  *
  * Exit from an interrupt handler, which might possibly result in entering
  * idle mode, in other words, leaving the mode in which read-side critical
  * sections can occur.  The caller must have disabled interrupts.
  *
  * This code assumes that the idle loop never does anything that might
  * result in unbalanced calls to irq_enter() and irq_exit().  If your
  * architecture's idle loop violates this assumption, RCU will give you what
  * you deserve, good and hard.  But very infrequently and irreproducibly.
  *
  * Use things like work queues to work around this limitation.
  *
  * You have been warned.
  *
  * If you add or remove a call to ct_irq_exit(), be sure to test with
  * CONFIG_RCU_EQS_DEBUG=y.
  */
 noinstr void ct_irq_exit(void)
 {
     lockdep_assert_irqs_disabled();
     ct_nmi_exit();
 }
 
 /*
  * Wrapper for ct_irq_enter() where interrupts are enabled.
  *
  * If you add or remove a call to ct_irq_enter_irqson(), be sure to test
  * with CONFIG_RCU_EQS_DEBUG=y.
  */
 void ct_irq_enter_irqson(void)
 {
     unsigned long flags;
 
     local_irq_save(flags);
     ct_irq_enter();
     local_irq_restore(flags);
 }
 
 /*
  * Wrapper for ct_irq_exit() where interrupts are enabled.
  *
  * If you add or remove a call to ct_irq_exit_irqson(), be sure to test
  * with CONFIG_RCU_EQS_DEBUG=y.
  */
 void ct_irq_exit_irqson(void)
 {
     unsigned long flags;
 
     local_irq_save(flags);
     ct_irq_exit();
     local_irq_restore(flags);
 }
 #else
 static __always_inline void ct_kernel_exit(bool user, int offset) { }
 static __always_inline void ct_kernel_enter(bool user, int offset) { }
 #endif /* #ifdef CONFIG_CONTEXT_TRACKING_IDLE */
 
 #ifdef CONFIG_CONTEXT_TRACKING_USER
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/context_tracking.h>
 
 DEFINE_STATIC_KEY_FALSE(context_tracking_key);
 EXPORT_SYMBOL_GPL(context_tracking_key);
 
 static noinstr bool context_tracking_recursion_enter(void)
 {
     int recursion;
 
     recursion = __this_cpu_inc_return(context_tracking.recursion);
     if (recursion == 1)
         return true;
 
     WARN_ONCE((recursion < 1), "Invalid context tracking recursion value %d\n", recursion);
     __this_cpu_dec(context_tracking.recursion);
 
     return false;
 }
 
 static __always_inline void context_tracking_recursion_exit(void)
 {
     __this_cpu_dec(context_tracking.recursion);
 }
 
 /**
  * __ct_user_enter - Inform the context tracking that the CPU is going
  *           to enter user or guest space mode.
  *
  * This function must be called right before we switch from the kernel
  * to user or guest space, when it's guaranteed the remaining kernel
  * instructions to execute won't use any RCU read side critical section
  * because this function sets RCU in extended quiescent state.
  */
 void noinstr __ct_user_enter(enum ctx_state state)
 {
     struct context_tracking *ct = this_cpu_ptr(&context_tracking);
     lockdep_assert_irqs_disabled();
 
     /* Kernel threads aren't supposed to go to userspace */
     WARN_ON_ONCE(!current->mm);
 
     if (!context_tracking_recursion_enter())
         return;
 
     if (__ct_state() != state) {
         if (ct->active) {
             /*
              * At this stage, only low level arch entry code remains and
              * then we'll run in userspace. We can assume there won't be
              * any RCU read-side critical section until the next call to
              * user_exit() or ct_irq_enter(). Let's remove RCU's dependency
              * on the tick.
              */
             if (state == CONTEXT_USER) {
                 instrumentation_begin();
                 trace_user_enter(0);
                 vtime_user_enter(current);
                 instrumentation_end();
             }
             /*
              * Other than generic entry implementation, we may be past the last
              * rescheduling opportunity in the entry code. Trigger a self IPI
              * that will fire and reschedule once we resume in user/guest mode.
              */
             rcu_irq_work_resched();
 
             /*
              * Enter RCU idle mode right before resuming userspace.  No use of RCU
              * is permitted between this call and rcu_eqs_exit(). This way the
              * CPU doesn't need to maintain the tick for RCU maintenance purposes
              * when the CPU runs in userspace.
              */
             ct_kernel_exit(true, RCU_DYNTICKS_IDX + state);
 
             /*
              * Special case if we only track user <-> kernel transitions for tickless
              * cputime accounting but we don't support RCU extended quiescent state.
              * In this we case we don't care about any concurrency/ordering.
              */
             if (!IS_ENABLED(CONFIG_CONTEXT_TRACKING_IDLE))
                 atomic_set(&ct->state, state);
         } else {
             /*
              * Even if context tracking is disabled on this CPU, because it's outside
              * the full dynticks mask for example, we still have to keep track of the
              * context transitions and states to prevent inconsistency on those of
              * other CPUs.
              * If a task triggers an exception in userspace, sleep on the exception
              * handler and then migrate to another CPU, that new CPU must know where
              * the exception returns by the time we call exception_exit().
              * This information can only be provided by the previous CPU when it called
              * exception_enter().
              * OTOH we can spare the calls to vtime and RCU when context_tracking.active
              * is false because we know that CPU is not tickless.
              */
             if (!IS_ENABLED(CONFIG_CONTEXT_TRACKING_IDLE)) {
                 /* Tracking for vtime only, no concurrent RCU EQS accounting */
                 atomic_set(&ct->state, state);
             } else {
                 /*
                  * Tracking for vtime and RCU EQS. Make sure we don't race
                  * with NMIs. OTOH we don't care about ordering here since
                  * RCU only requires RCU_DYNTICKS_IDX increments to be fully
                  * ordered.
                  */
                 atomic_add(state, &ct->state);
             }
         }
     }
     context_tracking_recursion_exit();
 }
 EXPORT_SYMBOL_GPL(__ct_user_enter);
 
 /*
  * OBSOLETE:
  * This function should be noinstr but the below local_irq_restore() is
  * unsafe because it involves illegal RCU uses through tracing and lockdep.
  * This is unlikely to be fixed as this function is obsolete. The preferred
  * way is to call __context_tracking_enter() through user_enter_irqoff()
  * or context_tracking_guest_enter(). It should be the arch entry code
  * responsibility to call into context tracking with IRQs disabled.
  */
 void ct_user_enter(enum ctx_state state)
 {
     unsigned long flags;
 
     /*
      * Some contexts may involve an exception occuring in an irq,
      * leading to that nesting:
      * ct_irq_enter() rcu_eqs_exit(true) rcu_eqs_enter(true) ct_irq_exit()
      * This would mess up the dyntick_nesting count though. And rcu_irq_*()
      * helpers are enough to protect RCU uses inside the exception. So
      * just return immediately if we detect we are in an IRQ.
      */
     if (in_interrupt())
         return;
 
     local_irq_save(flags);
     __ct_user_enter(state);
     local_irq_restore(flags);
 }
 NOKPROBE_SYMBOL(ct_user_enter);
 EXPORT_SYMBOL_GPL(ct_user_enter);
 
 /**
  * user_enter_callable() - Unfortunate ASM callable version of user_enter() for
  *             archs that didn't manage to check the context tracking
  *             static key from low level code.
  *
  * This OBSOLETE function should be noinstr but it unsafely calls
  * local_irq_restore(), involving illegal RCU uses through tracing and lockdep.
  * This is unlikely to be fixed as this function is obsolete. The preferred
  * way is to call user_enter_irqoff(). It should be the arch entry code
  * responsibility to call into context tracking with IRQs disabled.
  */
 void user_enter_callable(void)
 {
     user_enter();
 }
 NOKPROBE_SYMBOL(user_enter_callable);
 
 /**
  * __ct_user_exit - Inform the context tracking that the CPU is
  *          exiting user or guest mode and entering the kernel.
  *
  * This function must be called after we entered the kernel from user or
  * guest space before any use of RCU read side critical section. This
  * potentially include any high level kernel code like syscalls, exceptions,
  * signal handling, etc...
  *
  * This call supports re-entrancy. This way it can be called from any exception
  * handler without needing to know if we came from userspace or not.
  */
 void noinstr __ct_user_exit(enum ctx_state state)
 {
     struct context_tracking *ct = this_cpu_ptr(&context_tracking);
 
     if (!context_tracking_recursion_enter())
         return;
 
     if (__ct_state() == state) {
         if (ct->active) {
             /*
              * Exit RCU idle mode while entering the kernel because it can
              * run a RCU read side critical section anytime.
              */
             ct_kernel_enter(true, RCU_DYNTICKS_IDX - state);
             if (state == CONTEXT_USER) {
                 instrumentation_begin();
                 vtime_user_exit(current);
                 trace_user_exit(0);
                 instrumentation_end();
             }
 
             /*
              * Special case if we only track user <-> kernel transitions for tickless
              * cputime accounting but we don't support RCU extended quiescent state.
              * In this we case we don't care about any concurrency/ordering.
              */
             if (!IS_ENABLED(CONFIG_CONTEXT_TRACKING_IDLE))
                 atomic_set(&ct->state, CONTEXT_KERNEL);
 
         } else {
             if (!IS_ENABLED(CONFIG_CONTEXT_TRACKING_IDLE)) {
                 /* Tracking for vtime only, no concurrent RCU EQS accounting */
                 atomic_set(&ct->state, CONTEXT_KERNEL);
             } else {
                 /*
                  * Tracking for vtime and RCU EQS. Make sure we don't race
                  * with NMIs. OTOH we don't care about ordering here since
                  * RCU only requires RCU_DYNTICKS_IDX increments to be fully
                  * ordered.
                  */
                 atomic_sub(state, &ct->state);
             }
         }
     }
     context_tracking_recursion_exit();
 }
 EXPORT_SYMBOL_GPL(__ct_user_exit);
 
 /*
  * OBSOLETE:
  * This function should be noinstr but the below local_irq_save() is
  * unsafe because it involves illegal RCU uses through tracing and lockdep.
  * This is unlikely to be fixed as this function is obsolete. The preferred
  * way is to call __context_tracking_exit() through user_exit_irqoff()
  * or context_tracking_guest_exit(). It should be the arch entry code
  * responsibility to call into context tracking with IRQs disabled.
  */
 void ct_user_exit(enum ctx_state state)
 {
     unsigned long flags;
 
     if (in_interrupt())
         return;
 
     local_irq_save(flags);
     __ct_user_exit(state);
     local_irq_restore(flags);
 }
 NOKPROBE_SYMBOL(ct_user_exit);
 EXPORT_SYMBOL_GPL(ct_user_exit);
 
 /**
  * user_exit_callable() - Unfortunate ASM callable version of user_exit() for
  *            archs that didn't manage to check the context tracking
  *            static key from low level code.
  *
  * This OBSOLETE function should be noinstr but it unsafely calls local_irq_save(),
  * involving illegal RCU uses through tracing and lockdep. This is unlikely
  * to be fixed as this function is obsolete. The preferred way is to call
  * user_exit_irqoff(). It should be the arch entry code responsibility to
  * call into context tracking with IRQs disabled.
  */
 void user_exit_callable(void)
 {
     user_exit();
 }
 NOKPROBE_SYMBOL(user_exit_callable);
 
 void __init ct_cpu_track_user(int cpu)
 {
     static __initdata bool initialized = false;
 
     if (!per_cpu(context_tracking.active, cpu)) {
         per_cpu(context_tracking.active, cpu) = true;
         static_branch_inc(&context_tracking_key);
     }
 
     if (initialized)
         return;
 
 #ifdef CONFIG_HAVE_TIF_NOHZ
     /*
      * Set TIF_NOHZ to init/0 and let it propagate to all tasks through fork
      * This assumes that init is the only task at this early boot stage.
      */
     set_tsk_thread_flag(&init_task, TIF_NOHZ);
 #endif
     WARN_ON_ONCE(!tasklist_empty());
 
     initialized = true;
 }
 
 #ifdef CONFIG_CONTEXT_TRACKING_USER_FORCE
 void __init context_tracking_init(void)
 {
     int cpu;
 
     for_each_possible_cpu(cpu)
         ct_cpu_track_user(cpu);
 }
 #endif
 
 #endif /* #ifdef CONFIG_CONTEXT_TRACKING_USER */

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