diff options
Diffstat (limited to 'kernel/rcu')
| -rw-r--r-- | kernel/rcu/rcu.h | 27 | ||||
| -rw-r--r-- | kernel/rcu/tree.c | 40 | ||||
| -rw-r--r-- | kernel/rcu/tree.h | 1 |
3 files changed, 21 insertions, 47 deletions
diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h index f4a411964c41..afe0559d1867 100644 --- a/kernel/rcu/rcu.h +++ b/kernel/rcu/rcu.h @@ -30,32 +30,7 @@ #define RCU_TRACE(stmt) #endif /* #else #ifdef CONFIG_RCU_TRACE */ -/* - * Process-level increment to ->dynticks_nesting field. This allows for - * architectures that use half-interrupts and half-exceptions from - * process context. - * - * DYNTICK_TASK_NEST_MASK defines a field of width DYNTICK_TASK_NEST_WIDTH - * that counts the number of process-based reasons why RCU cannot - * consider the corresponding CPU to be idle, and DYNTICK_TASK_NEST_VALUE - * is the value used to increment or decrement this field. - * - * The rest of the bits could in principle be used to count interrupts, - * but this would mean that a negative-one value in the interrupt - * field could incorrectly zero out the DYNTICK_TASK_NEST_MASK field. - * We therefore provide a two-bit guard field defined by DYNTICK_TASK_MASK - * that is set to DYNTICK_TASK_FLAG upon initial exit from idle. - * The DYNTICK_TASK_EXIT_IDLE value is thus the combined value used upon - * initial exit from idle. - */ -#define DYNTICK_TASK_NEST_WIDTH 7 -#define DYNTICK_TASK_NEST_VALUE ((LLONG_MAX >> DYNTICK_TASK_NEST_WIDTH) + 1) -#define DYNTICK_TASK_NEST_MASK (LLONG_MAX - DYNTICK_TASK_NEST_VALUE + 1) -#define DYNTICK_TASK_FLAG ((DYNTICK_TASK_NEST_VALUE / 8) * 2) -#define DYNTICK_TASK_MASK ((DYNTICK_TASK_NEST_VALUE / 8) * 3) -#define DYNTICK_TASK_EXIT_IDLE (DYNTICK_TASK_NEST_VALUE + \ - DYNTICK_TASK_FLAG) - +/* Offset to allow for unmatched rcu_irq_{enter,exit}(). */ #define DYNTICK_IRQ_NONIDLE ((INT_MAX / 2) + 1) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index fde0e840563f..d123474fe829 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -265,7 +265,7 @@ void rcu_bh_qs(void) #endif static DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = { - .dynticks_nesting = DYNTICK_TASK_EXIT_IDLE, + .dynticks_nesting = 1, .dynticks_nmi_nesting = DYNTICK_IRQ_NONIDLE, .dynticks = ATOMIC_INIT(RCU_DYNTICK_CTRL_CTR), }; @@ -813,6 +813,10 @@ static void rcu_eqs_enter_common(bool user) /* * 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 rcu_eqs_enter(bool user) { @@ -821,11 +825,11 @@ static void rcu_eqs_enter(bool user) rdtp = this_cpu_ptr(&rcu_dynticks); WRITE_ONCE(rdtp->dynticks_nmi_nesting, 0); WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && - (rdtp->dynticks_nesting & DYNTICK_TASK_NEST_MASK) == 0); - if ((rdtp->dynticks_nesting & DYNTICK_TASK_NEST_MASK) == DYNTICK_TASK_NEST_VALUE) + rdtp->dynticks_nesting == 0); + if (rdtp->dynticks_nesting == 1) rcu_eqs_enter_common(user); else - rdtp->dynticks_nesting -= DYNTICK_TASK_NEST_VALUE; + rdtp->dynticks_nesting--; } /** @@ -836,10 +840,6 @@ static void rcu_eqs_enter(bool user) * critical sections can occur in irq handlers in idle, a possibility * handled by irq_enter() and irq_exit().) * - * We crowbar the ->dynticks_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. - * * If you add or remove a call to rcu_idle_enter(), be sure to test with * CONFIG_RCU_EQS_DEBUG=y. */ @@ -984,6 +984,10 @@ static void rcu_eqs_exit_common(long long newval, int user) /* * 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 rcu_eqs_exit(bool user) { @@ -994,12 +998,12 @@ static void rcu_eqs_exit(bool user) rdtp = this_cpu_ptr(&rcu_dynticks); oldval = rdtp->dynticks_nesting; WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && oldval < 0); - if (oldval & DYNTICK_TASK_NEST_MASK) { - rdtp->dynticks_nesting += DYNTICK_TASK_NEST_VALUE; + if (oldval) { + rdtp->dynticks_nesting++; } else { __this_cpu_inc(disable_rcu_irq_enter); - rcu_eqs_exit_common(DYNTICK_TASK_EXIT_IDLE, user); - rdtp->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE; + rcu_eqs_exit_common(1, user); + rdtp->dynticks_nesting = 1; __this_cpu_dec(disable_rcu_irq_enter); WRITE_ONCE(rdtp->dynticks_nmi_nesting, DYNTICK_IRQ_NONIDLE); } @@ -1011,11 +1015,6 @@ static void rcu_eqs_exit(bool user) * Exit idle mode, in other words, -enter- the mode in which RCU * read-side critical sections can occur. * - * We crowbar the ->dynticks_nesting field to DYNTICK_TASK_NEST 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. - * * If you add or remove a call to rcu_idle_exit(), be sure to test with * CONFIG_RCU_EQS_DEBUG=y. */ @@ -1219,7 +1218,8 @@ EXPORT_SYMBOL_GPL(rcu_lockdep_current_cpu_online); */ static int rcu_is_cpu_rrupt_from_idle(void) { - return __this_cpu_read(rcu_dynticks.dynticks_nesting) <= 1; + return __this_cpu_read(rcu_dynticks.dynticks_nesting) <= 0 && + __this_cpu_read(rcu_dynticks.dynticks_nmi_nesting) <= 1; } /* @@ -3709,7 +3709,7 @@ rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp) raw_spin_lock_irqsave_rcu_node(rnp, flags); rdp->grpmask = leaf_node_cpu_bit(rdp->mynode, cpu); rdp->dynticks = &per_cpu(rcu_dynticks, cpu); - WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != DYNTICK_TASK_EXIT_IDLE); + WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != 1); WARN_ON_ONCE(rcu_dynticks_in_eqs(rcu_dynticks_snap(rdp->dynticks))); rdp->cpu = cpu; rdp->rsp = rsp; @@ -3738,7 +3738,7 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp) if (rcu_segcblist_empty(&rdp->cblist) && /* No early-boot CBs? */ !init_nocb_callback_list(rdp)) rcu_segcblist_init(&rdp->cblist); /* Re-enable callbacks. */ - rdp->dynticks->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE; + rdp->dynticks->dynticks_nesting = 1; rcu_dynticks_eqs_online(); raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */ diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h index 46a5d1991450..dbd7e3753bed 100644 --- a/kernel/rcu/tree.h +++ b/kernel/rcu/tree.h @@ -39,7 +39,6 @@ */ struct rcu_dynticks { long long dynticks_nesting; /* Track irq/process nesting level. */ - /* Process level is worth LLONG_MAX/2. */ int dynticks_nmi_nesting; /* Track NMI nesting level. */ atomic_t dynticks; /* Even value for idle, else odd. */ bool rcu_need_heavy_qs; /* GP old, need heavy quiescent state. */ |