On Tue, May 05, 2020 at 03:16:27PM +0200, Thomas Gleixner wrote: > These functions are invoked from context tracking and other places in the > low level entry code. Move them into the .noinstr.text section to exclude > them from instrumentation. > > Mark the places which are safe to invoke traceable functions with > instr_begin/end() so objtool won't complain. > > Signed-off-by: Thomas Gleixner <[email protected]>
Acked-by: Paul E. McKenney <[email protected]> > --- > kernel/rcu/tree.c | 85 > +++++++++++++++++++++++++---------------------- > kernel/rcu/tree_plugin.h | 4 +- > kernel/rcu/update.c | 7 +-- > 3 files changed, 52 insertions(+), 44 deletions(-) > > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -75,9 +75,6 @@ > */ > #define RCU_DYNTICK_CTRL_MASK 0x1 > #define RCU_DYNTICK_CTRL_CTR (RCU_DYNTICK_CTRL_MASK + 1) > -#ifndef rcu_eqs_special_exit > -#define rcu_eqs_special_exit() do { } while (0) > -#endif Joel has a patch series doing a more thorough removal of this function, but sometimes it is necessary to remove the function twice, just to be sure. ;-) > static DEFINE_PER_CPU_SHARED_ALIGNED(struct rcu_data, rcu_data) = { > .dynticks_nesting = 1, > @@ -229,7 +226,7 @@ void rcu_softirq_qs(void) > * RCU is watching prior to the call to this function and is no longer > * watching upon return. > */ > -static void rcu_dynticks_eqs_enter(void) > +static noinstr void rcu_dynticks_eqs_enter(void) > { > struct rcu_data *rdp = this_cpu_ptr(&rcu_data); > int seq; > @@ -253,7 +250,7 @@ static void rcu_dynticks_eqs_enter(void) > * 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 void rcu_dynticks_eqs_exit(void) > +static noinstr void rcu_dynticks_eqs_exit(void) > { > struct rcu_data *rdp = this_cpu_ptr(&rcu_data); > int seq; > @@ -270,8 +267,6 @@ static void rcu_dynticks_eqs_exit(void) > if (seq & RCU_DYNTICK_CTRL_MASK) { > atomic_andnot(RCU_DYNTICK_CTRL_MASK, &rdp->dynticks); > smp_mb__after_atomic(); /* _exit after clearing mask. */ > - /* Prefer duplicate flushes to losing a flush. */ > - rcu_eqs_special_exit(); > } > } > > @@ -299,7 +294,7 @@ static void rcu_dynticks_eqs_online(void > * > * No ordering, as we are sampling CPU-local information. > */ > -static bool rcu_dynticks_curr_cpu_in_eqs(void) > +static __always_inline bool rcu_dynticks_curr_cpu_in_eqs(void) > { > struct rcu_data *rdp = this_cpu_ptr(&rcu_data); > > @@ -566,7 +561,7 @@ EXPORT_SYMBOL_GPL(rcutorture_get_gp_data > * the possibility of usermode upcalls having messed up our count > * of interrupt nesting level during the prior busy period. > */ > -static void rcu_eqs_enter(bool user) > +static noinstr void rcu_eqs_enter(bool user) > { > struct rcu_data *rdp = this_cpu_ptr(&rcu_data); > > @@ -581,12 +576,14 @@ static void rcu_eqs_enter(bool user) > } > > lockdep_assert_irqs_disabled(); > + instr_begin(); > trace_rcu_dyntick(TPS("Start"), rdp->dynticks_nesting, 0, > atomic_read(&rdp->dynticks)); > WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && > !is_idle_task(current)); > rdp = this_cpu_ptr(&rcu_data); > do_nocb_deferred_wakeup(rdp); > rcu_prepare_for_idle(); > rcu_preempt_deferred_qs(current); > + instr_end(); > WRITE_ONCE(rdp->dynticks_nesting, 0); /* Avoid irq-access tearing. */ > // RCU is watching here ... > rcu_dynticks_eqs_enter(); > @@ -623,7 +620,7 @@ void rcu_idle_enter(void) > * If you add or remove a call to rcu_user_enter(), be sure to test with > * CONFIG_RCU_EQS_DEBUG=y. > */ > -void rcu_user_enter(void) > +noinstr void rcu_user_enter(void) > { > lockdep_assert_irqs_disabled(); > rcu_eqs_enter(true); > @@ -656,19 +653,23 @@ static __always_inline void rcu_nmi_exit > * leave it in non-RCU-idle state. > */ > if (rdp->dynticks_nmi_nesting != 1) { > + instr_begin(); > trace_rcu_dyntick(TPS("--="), rdp->dynticks_nmi_nesting, > rdp->dynticks_nmi_nesting - 2, > atomic_read(&rdp->dynticks)); > WRITE_ONCE(rdp->dynticks_nmi_nesting, /* No store tearing. */ > rdp->dynticks_nmi_nesting - 2); > + instr_end(); > return; > } > > + instr_begin(); > /* This NMI interrupted an RCU-idle CPU, restore RCU-idleness. */ > trace_rcu_dyntick(TPS("Startirq"), rdp->dynticks_nmi_nesting, 0, > atomic_read(&rdp->dynticks)); > WRITE_ONCE(rdp->dynticks_nmi_nesting, 0); /* Avoid store tearing. */ > > if (irq) > rcu_prepare_for_idle(); > + instr_end(); > > // RCU is watching here ... > rcu_dynticks_eqs_enter(); > @@ -684,7 +685,7 @@ static __always_inline void rcu_nmi_exit > * If you add or remove a call to rcu_nmi_exit(), be sure to test > * with CONFIG_RCU_EQS_DEBUG=y. > */ > -void rcu_nmi_exit(void) > +void noinstr rcu_nmi_exit(void) > { > rcu_nmi_exit_common(false); > } > @@ -708,7 +709,7 @@ void rcu_nmi_exit(void) > * If you add or remove a call to rcu_irq_exit(), be sure to test with > * CONFIG_RCU_EQS_DEBUG=y. > */ > -void rcu_irq_exit(void) > +void noinstr rcu_irq_exit(void) > { > lockdep_assert_irqs_disabled(); > rcu_nmi_exit_common(true); > @@ -737,7 +738,7 @@ void rcu_irq_exit_irqson(void) > * 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 rcu_eqs_exit(bool user) > +static void noinstr rcu_eqs_exit(bool user) > { > struct rcu_data *rdp; > long oldval; > @@ -755,12 +756,14 @@ static void rcu_eqs_exit(bool user) > // RCU is not watching here ... > rcu_dynticks_eqs_exit(); > // ... but is watching here. > + instr_begin(); > rcu_cleanup_after_idle(); > trace_rcu_dyntick(TPS("End"), rdp->dynticks_nesting, 1, > atomic_read(&rdp->dynticks)); > WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && > !is_idle_task(current)); > WRITE_ONCE(rdp->dynticks_nesting, 1); > WARN_ON_ONCE(rdp->dynticks_nmi_nesting); > WRITE_ONCE(rdp->dynticks_nmi_nesting, DYNTICK_IRQ_NONIDLE); > + instr_end(); > } > > /** > @@ -791,7 +794,7 @@ void rcu_idle_exit(void) > * If you add or remove a call to rcu_user_exit(), be sure to test with > * CONFIG_RCU_EQS_DEBUG=y. > */ > -void rcu_user_exit(void) > +void noinstr rcu_user_exit(void) > { > rcu_eqs_exit(1); > } > @@ -839,28 +842,35 @@ static __always_inline void rcu_nmi_ente > rcu_cleanup_after_idle(); > > incby = 1; > - } else if (irq && tick_nohz_full_cpu(rdp->cpu) && > - rdp->dynticks_nmi_nesting == DYNTICK_IRQ_NONIDLE && > - READ_ONCE(rdp->rcu_urgent_qs) && > - !READ_ONCE(rdp->rcu_forced_tick)) { > - // We get here only if we had already exited the extended > - // quiescent state and this was an interrupt (not an NMI). > - // Therefore, (1) RCU is already watching and (2) The fact > - // that we are in an interrupt handler and that the rcu_node > - // lock is an irq-disabled lock prevents self-deadlock. > - // So we can safely recheck under the lock. > - raw_spin_lock_rcu_node(rdp->mynode); > - if (rdp->rcu_urgent_qs && !rdp->rcu_forced_tick) { > - // A nohz_full CPU is in the kernel and RCU > - // needs a quiescent state. Turn on the tick! > - WRITE_ONCE(rdp->rcu_forced_tick, true); > - tick_dep_set_cpu(rdp->cpu, TICK_DEP_BIT_RCU); > + } else if (irq) { > + instr_begin(); > + if (tick_nohz_full_cpu(rdp->cpu) && > + rdp->dynticks_nmi_nesting == DYNTICK_IRQ_NONIDLE && > + READ_ONCE(rdp->rcu_urgent_qs) && > + !READ_ONCE(rdp->rcu_forced_tick)) { > + // We get here only if we had already exited the > + // extended quiescent state and this was an > + // interrupt (not an NMI). Therefore, (1) RCU is > + // already watching and (2) The fact that we are in > + // an interrupt handler and that the rcu_node lock > + // is an irq-disabled lock prevents self-deadlock. > + // So we can safely recheck under the lock. > + raw_spin_lock_rcu_node(rdp->mynode); > + if (rdp->rcu_urgent_qs && !rdp->rcu_forced_tick) { > + // A nohz_full CPU is in the kernel and RCU > + // needs a quiescent state. Turn on the tick! > + WRITE_ONCE(rdp->rcu_forced_tick, true); > + tick_dep_set_cpu(rdp->cpu, TICK_DEP_BIT_RCU); > + } > + raw_spin_unlock_rcu_node(rdp->mynode); > } > - raw_spin_unlock_rcu_node(rdp->mynode); > + instr_end(); > } > + instr_begin(); > trace_rcu_dyntick(incby == 1 ? TPS("Endirq") : TPS("++="), > rdp->dynticks_nmi_nesting, > rdp->dynticks_nmi_nesting + incby, > atomic_read(&rdp->dynticks)); > + instr_end(); > WRITE_ONCE(rdp->dynticks_nmi_nesting, /* Prevent store tearing. */ > rdp->dynticks_nmi_nesting + incby); > barrier(); > @@ -869,11 +879,10 @@ static __always_inline void rcu_nmi_ente > /** > * rcu_nmi_enter - inform RCU of entry to NMI context > */ > -void rcu_nmi_enter(void) > +noinstr void rcu_nmi_enter(void) > { > rcu_nmi_enter_common(false); > } > -NOKPROBE_SYMBOL(rcu_nmi_enter); > > /** > * rcu_irq_enter - inform RCU that current CPU is entering irq away from idle > @@ -897,7 +906,7 @@ NOKPROBE_SYMBOL(rcu_nmi_enter); > * If you add or remove a call to rcu_irq_enter(), be sure to test with > * CONFIG_RCU_EQS_DEBUG=y. > */ > -void rcu_irq_enter(void) > +noinstr void rcu_irq_enter(void) > { > lockdep_assert_irqs_disabled(); > rcu_nmi_enter_common(true); > @@ -942,7 +951,7 @@ static void rcu_disable_urgency_upon_qs( > * if the current CPU is not in its idle loop or is in an interrupt or > * NMI handler, return true. > */ > -bool notrace rcu_is_watching(void) > +noinstr bool rcu_is_watching(void) > { > bool ret; > > @@ -986,7 +995,7 @@ void rcu_request_urgent_qs_task(struct t > * RCU on an offline processor during initial boot, hence the check for > * rcu_scheduler_fully_active. > */ > -bool rcu_lockdep_current_cpu_online(void) > +noinstr bool rcu_lockdep_current_cpu_online(void) > { > struct rcu_data *rdp; > struct rcu_node *rnp; > @@ -994,12 +1003,12 @@ bool rcu_lockdep_current_cpu_online(void > > if (in_nmi() || !rcu_scheduler_fully_active) > return true; > - preempt_disable(); > + preempt_disable_notrace(); > rdp = this_cpu_ptr(&rcu_data); > rnp = rdp->mynode; > if (rdp->grpmask & rcu_rnp_online_cpus(rnp)) > ret = true; > - preempt_enable(); > + preempt_enable_notrace(); > return ret; > } > EXPORT_SYMBOL_GPL(rcu_lockdep_current_cpu_online); > --- a/kernel/rcu/tree_plugin.h > +++ b/kernel/rcu/tree_plugin.h > @@ -2553,7 +2553,7 @@ static void rcu_bind_gp_kthread(void) > } > > /* Record the current task on dyntick-idle entry. */ > -static void rcu_dynticks_task_enter(void) > +static void noinstr 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()); > @@ -2561,7 +2561,7 @@ static void rcu_dynticks_task_enter(void > } > > /* Record no current task on dyntick-idle exit. */ > -static void rcu_dynticks_task_exit(void) > +static void noinstr rcu_dynticks_task_exit(void) > { > #if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL) > WRITE_ONCE(current->rcu_tasks_idle_cpu, -1); > --- a/kernel/rcu/update.c > +++ b/kernel/rcu/update.c > @@ -95,7 +95,7 @@ module_param(rcu_normal_after_boot, int, > * Similarly, we avoid claiming an RCU read lock held if the current > * CPU is offline. > */ > -static bool rcu_read_lock_held_common(bool *ret) > +static noinstr bool rcu_read_lock_held_common(bool *ret) > { > if (!debug_lockdep_rcu_enabled()) { > *ret = 1; > @@ -112,7 +112,7 @@ static bool rcu_read_lock_held_common(bo > return false; > } > > -int rcu_read_lock_sched_held(void) > +noinstr int rcu_read_lock_sched_held(void) > { > bool ret; > > @@ -270,13 +270,12 @@ struct lockdep_map rcu_callback_map = > STATIC_LOCKDEP_MAP_INIT("rcu_callback", &rcu_callback_key); > EXPORT_SYMBOL_GPL(rcu_callback_map); > > -int notrace debug_lockdep_rcu_enabled(void) > +noinstr int notrace debug_lockdep_rcu_enabled(void) > { > return rcu_scheduler_active != RCU_SCHEDULER_INACTIVE && debug_locks && > current->lockdep_recursion == 0; > } > EXPORT_SYMBOL_GPL(debug_lockdep_rcu_enabled); > -NOKPROBE_SYMBOL(debug_lockdep_rcu_enabled); > > /** > * rcu_read_lock_held() - might we be in RCU read-side critical section? >
