diff options
| -rw-r--r-- | Documentation/RCU/trace.txt | 17 | ||||
| -rw-r--r-- | kernel/rcutree.c | 130 | ||||
| -rw-r--r-- | kernel/rcutree.h | 9 | ||||
| -rw-r--r-- | kernel/rcutree_plugin.h | 7 | ||||
| -rw-r--r-- | kernel/rcutree_trace.c | 12 | ||||
| -rw-r--r-- | lib/locking-selftest.c | 2 |
6 files changed, 74 insertions, 103 deletions
diff --git a/Documentation/RCU/trace.txt b/Documentation/RCU/trace.txt index c078ad48f7a1..8173cec473aa 100644 --- a/Documentation/RCU/trace.txt +++ b/Documentation/RCU/trace.txt @@ -99,18 +99,11 @@ o "qp" indicates that RCU still expects a quiescent state from o "dt" is the current value of the dyntick counter that is incremented when entering or leaving dynticks idle state, either by the - scheduler or by irq. The number after the "/" is the interrupt - nesting depth when in dyntick-idle state, or one greater than - the interrupt-nesting depth otherwise. - - This field is displayed only for CONFIG_NO_HZ kernels. - -o "dn" is the current value of the dyntick counter that is incremented - when entering or leaving dynticks idle state via NMI. If both - the "dt" and "dn" values are even, then this CPU is in dynticks - idle mode and may be ignored by RCU. If either of these two - counters is odd, then RCU must be alert to the possibility of - an RCU read-side critical section running on this CPU. + scheduler or by irq. This number is even if the CPU is in + dyntick idle mode and odd otherwise. The number after the first + "/" is the interrupt nesting depth when in dyntick-idle state, + or one greater than the interrupt-nesting depth otherwise. + The number after the second "/" is the NMI nesting depth. This field is displayed only for CONFIG_NO_HZ kernels. diff --git a/kernel/rcutree.c b/kernel/rcutree.c index f07d2f03181a..8154a4a3491c 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -163,7 +163,7 @@ EXPORT_SYMBOL_GPL(rcu_note_context_switch); #ifdef CONFIG_NO_HZ DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = { .dynticks_nesting = 1, - .dynticks = 1, + .dynticks = ATOMIC_INIT(1), }; #endif /* #ifdef CONFIG_NO_HZ */ @@ -322,13 +322,25 @@ void rcu_enter_nohz(void) unsigned long flags; struct rcu_dynticks *rdtp; - smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */ local_irq_save(flags); rdtp = &__get_cpu_var(rcu_dynticks); - rdtp->dynticks++; - rdtp->dynticks_nesting--; - WARN_ON_ONCE(rdtp->dynticks & 0x1); + if (--rdtp->dynticks_nesting) { + local_irq_restore(flags); + return; + } + /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */ + smp_mb__before_atomic_inc(); /* See above. */ + atomic_inc(&rdtp->dynticks); + smp_mb__after_atomic_inc(); /* Force ordering with next sojourn. */ + WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1); local_irq_restore(flags); + + /* If the interrupt queued a callback, get out of dyntick mode. */ + if (in_irq() && + (__get_cpu_var(rcu_sched_data).nxtlist || + __get_cpu_var(rcu_bh_data).nxtlist || + rcu_preempt_needs_cpu(smp_processor_id()))) + set_need_resched(); } /* @@ -344,11 +356,16 @@ void rcu_exit_nohz(void) local_irq_save(flags); rdtp = &__get_cpu_var(rcu_dynticks); - rdtp->dynticks++; - rdtp->dynticks_nesting++; - WARN_ON_ONCE(!(rdtp->dynticks & 0x1)); + if (rdtp->dynticks_nesting++) { + local_irq_restore(flags); + return; + } + smp_mb__before_atomic_inc(); /* Force ordering w/previous sojourn. */ + atomic_inc(&rdtp->dynticks); + /* CPUs seeing atomic_inc() must see later RCU read-side crit sects */ + smp_mb__after_atomic_inc(); /* See above. */ + WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1)); local_irq_restore(flags); - smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */ } /** @@ -362,11 +379,15 @@ void rcu_nmi_enter(void) { struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); - if (rdtp->dynticks & 0x1) + if (rdtp->dynticks_nmi_nesting == 0 && + (atomic_read(&rdtp->dynticks) & 0x1)) return; - rdtp->dynticks_nmi++; - WARN_ON_ONCE(!(rdtp->dynticks_nmi & 0x1)); - smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */ + rdtp->dynticks_nmi_nesting++; + smp_mb__before_atomic_inc(); /* Force delay from prior write. */ + atomic_inc(&rdtp->dynticks); + /* CPUs seeing atomic_inc() must see later RCU read-side crit sects */ + smp_mb__after_atomic_inc(); /* See above. */ + WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1)); } /** @@ -380,11 +401,14 @@ void rcu_nmi_exit(void) { struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); - if (rdtp->dynticks & 0x1) + if (rdtp->dynticks_nmi_nesting == 0 || + --rdtp->dynticks_nmi_nesting != 0) return; - smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */ - rdtp->dynticks_nmi++; - WARN_ON_ONCE(rdtp->dynticks_nmi & 0x1); + /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */ + smp_mb__before_atomic_inc(); /* See above. */ + atomic_inc(&rdtp->dynticks); + smp_mb__after_atomic_inc(); /* Force delay to next write. */ + WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1); } /** @@ -395,13 +419,7 @@ void rcu_nmi_exit(void) */ void rcu_irq_enter(void) { - struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); - - if (rdtp->dynticks_nesting++) - return; - rdtp->dynticks++; - WARN_ON_ONCE(!(rdtp->dynticks & 0x1)); - smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */ + rcu_exit_nohz(); } /** @@ -413,18 +431,7 @@ void rcu_irq_enter(void) */ void rcu_irq_exit(void) { - struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); - - if (--rdtp->dynticks_nesting) - return; - smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */ - rdtp->dynticks++; - WARN_ON_ONCE(rdtp->dynticks & 0x1); - - /* If the interrupt queued a callback, get out of dyntick mode. */ - if (__this_cpu_read(rcu_sched_data.nxtlist) || - __this_cpu_read(rcu_bh_data.nxtlist)) - set_need_resched(); + rcu_enter_nohz(); } #ifdef CONFIG_SMP @@ -436,19 +443,8 @@ void rcu_irq_exit(void) */ static int dyntick_save_progress_counter(struct rcu_data *rdp) { - int ret; - int snap; - int snap_nmi; - - snap = rdp->dynticks->dynticks; - snap_nmi = rdp->dynticks->dynticks_nmi; - smp_mb(); /* Order sampling of snap with end of grace period. */ - rdp->dynticks_snap = snap; - rdp->dynticks_nmi_snap = snap_nmi; - ret = ((snap & 0x1) == 0) && ((snap_nmi & 0x1) == 0); - if (ret) - rdp->dynticks_fqs++; - return ret; + rdp->dynticks_snap = atomic_add_return(0, &rdp->dynticks->dynticks); + return 0; } /* @@ -459,16 +455,11 @@ static int dyntick_save_progress_counter(struct rcu_data *rdp) */ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) { - long curr; - long curr_nmi; - long snap; - long snap_nmi; + unsigned long curr; + unsigned long snap; - curr = rdp->dynticks->dynticks; - snap = rdp->dynticks_snap; - curr_nmi = rdp->dynticks->dynticks_nmi; - snap_nmi = rdp->dynticks_nmi_snap; - smp_mb(); /* force ordering with cpu entering/leaving dynticks. */ + curr = (unsigned long)atomic_add_return(0, &rdp->dynticks->dynticks); + snap = (unsigned long)rdp->dynticks_snap; /* * If the CPU passed through or entered a dynticks idle phase with @@ -478,8 +469,7 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) * read-side critical section that started before the beginning * of the current RCU grace period. */ - if ((curr != snap || (curr & 0x1) == 0) && - (curr_nmi != snap_nmi || (curr_nmi & 0x1) == 0)) { + if ((curr & 0x1) == 0 || ULONG_CMP_GE(curr, snap + 2)) { rdp->dynticks_fqs++; return 1; } @@ -908,6 +898,12 @@ static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags) unsigned long gp_duration; WARN_ON_ONCE(!rcu_gp_in_progress(rsp)); + + /* + * Ensure that all grace-period and pre-grace-period activity + * is seen before the assignment to rsp->completed. + */ + smp_mb(); /* See above block comment. */ gp_duration = jiffies - rsp->gp_start; if (gp_duration > rsp->gp_max) rsp->gp_max = gp_duration; @@ -1455,25 +1451,11 @@ __rcu_process_callbacks(struct rcu_state *rsp, struct rcu_data *rdp) */ static void rcu_process_callbacks(void) { - /* - * Memory references from any prior RCU read-side critical sections - * executed by the interrupted code must be seen before any RCU - * grace-period manipulations below. - */ - smp_mb(); /* See above block comment. */ - __rcu_process_callbacks(&rcu_sched_state, &__get_cpu_var(rcu_sched_data)); __rcu_process_callbacks(&rcu_bh_state, &__get_cpu_var(rcu_bh_data)); rcu_preempt_process_callbacks(); - /* - * Memory references from any later RCU read-side critical sections - * executed by the interrupted code must be seen after any RCU - * grace-period manipulations above. - */ - smp_mb(); /* See above block comment. */ - /* If we are last CPU on way to dyntick-idle mode, accelerate it. */ rcu_needs_cpu_flush(); } diff --git a/kernel/rcutree.h b/kernel/rcutree.h index 257664815d5d..93d4a1c2e88b 100644 --- a/kernel/rcutree.h +++ b/kernel/rcutree.h @@ -84,11 +84,9 @@ * Dynticks per-CPU state. */ struct rcu_dynticks { - int dynticks_nesting; /* Track nesting level, sort of. */ - int dynticks; /* Even value for dynticks-idle, else odd. */ - int dynticks_nmi; /* Even value for either dynticks-idle or */ - /* not in nmi handler, else odd. So this */ - /* remains even for nmi from irq handler. */ + int dynticks_nesting; /* Track irq/process nesting level. */ + int dynticks_nmi_nesting; /* Track NMI nesting level. */ + atomic_t dynticks; /* Even value for dynticks-idle, else odd. */ }; /* RCU's kthread states for tracing. */ @@ -284,7 +282,6 @@ struct rcu_data { /* 3) dynticks interface. */ struct rcu_dynticks *dynticks; /* Shared per-CPU dynticks state. */ int dynticks_snap; /* Per-GP tracking for dynticks. */ - int dynticks_nmi_snap; /* Per-GP tracking for dynticks_nmi. */ #endif /* #ifdef CONFIG_NO_HZ */ /* 4) reasons this CPU needed to be kicked by force_quiescent_state */ diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h index 3f6559a5f5cd..ed339702481d 100644 --- a/kernel/rcutree_plugin.h +++ b/kernel/rcutree_plugin.h @@ -1520,7 +1520,6 @@ int rcu_needs_cpu(int cpu) { int c = 0; int snap; - int snap_nmi; int thatcpu; /* Check for being in the holdoff period. */ @@ -1531,10 +1530,10 @@ int rcu_needs_cpu(int cpu) for_each_online_cpu(thatcpu) { if (thatcpu == cpu) continue; - snap = per_cpu(rcu_dynticks, thatcpu).dynticks; - snap_nmi = per_cpu(rcu_dynticks, thatcpu).dynticks_nmi; + snap = atomic_add_return(0, &per_cpu(rcu_dynticks, + thatcpu).dynticks); smp_mb(); /* Order sampling of snap with end of grace period. */ - if (((snap & 0x1) != 0) || ((snap_nmi & 0x1) != 0)) { + if ((snap & 0x1) != 0) { per_cpu(rcu_dyntick_drain, cpu) = 0; per_cpu(rcu_dyntick_holdoff, cpu) = jiffies - 1; return rcu_needs_cpu_quick_check(cpu); diff --git a/kernel/rcutree_trace.c b/kernel/rcutree_trace.c index aa0fd72b4bc7..9678cc3650f5 100644 --- a/kernel/rcutree_trace.c +++ b/kernel/rcutree_trace.c @@ -69,10 +69,10 @@ static void print_one_rcu_data(struct seq_file *m, struct rcu_data *rdp) rdp->passed_quiesc, rdp->passed_quiesc_completed, rdp->qs_pending); #ifdef CONFIG_NO_HZ - seq_printf(m, " dt=%d/%d dn=%d df=%lu", - rdp->dynticks->dynticks, + seq_printf(m, " dt=%d/%d/%d df=%lu", + atomic_read(&rdp->dynticks->dynticks), rdp->dynticks->dynticks_nesting, - rdp->dynticks->dynticks_nmi, + rdp->dynticks->dynticks_nmi_nesting, rdp->dynticks_fqs); #endif /* #ifdef CONFIG_NO_HZ */ seq_printf(m, " of=%lu ri=%lu", rdp->offline_fqs, rdp->resched_ipi); @@ -141,9 +141,9 @@ static void print_one_rcu_data_csv(struct seq_file *m, struct rcu_data *rdp) rdp->qs_pending); #ifdef CONFIG_NO_HZ seq_printf(m, ",%d,%d,%d,%lu", - rdp->dynticks->dynticks, + atomic_read(&rdp->dynticks->dynticks), rdp->dynticks->dynticks_nesting, - rdp->dynticks->dynticks_nmi, + rdp->dynticks->dynticks_nmi_nesting, rdp->dynticks_fqs); #endif /* #ifdef CONFIG_NO_HZ */ seq_printf(m, ",%lu,%lu", rdp->offline_fqs, rdp->resched_ipi); @@ -167,7 +167,7 @@ static int show_rcudata_csv(struct seq_file *m, void *unused) { seq_puts(m, "\"CPU\",\"Online?\",\"c\",\"g\",\"pq\",\"pqc\",\"pq\","); #ifdef CONFIG_NO_HZ - seq_puts(m, "\"dt\",\"dt nesting\",\"dn\",\"df\","); + seq_puts(m, "\"dt\",\"dt nesting\",\"dt NMI nesting\",\"df\","); #endif /* #ifdef CONFIG_NO_HZ */ seq_puts(m, "\"of\",\"ri\",\"ql\",\"b\",\"ci\",\"co\",\"ca\"\n"); #ifdef CONFIG_TREE_PREEMPT_RCU diff --git a/lib/locking-selftest.c b/lib/locking-selftest.c index 619313ed6c46..507a22fab738 100644 --- a/lib/locking-selftest.c +++ b/lib/locking-selftest.c @@ -144,7 +144,7 @@ static void init_shared_classes(void) #define HARDIRQ_ENTER() \ local_irq_disable(); \ - irq_enter(); \ + __irq_enter(); \ WARN_ON(!in_irq()); #define HARDIRQ_EXIT() \ |