diff options
| -rw-r--r-- | kernel/rcu/rcu.h | 2 | ||||
| -rw-r--r-- | kernel/rcu/tasks.h | 36 | ||||
| -rw-r--r-- | kernel/rcu/tree.c | 24 | ||||
| -rw-r--r-- | kernel/rcu/tree.h | 2 | ||||
| -rw-r--r-- | kernel/rcu/tree_plugin.h | 18 |
5 files changed, 72 insertions, 10 deletions
diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h index e1089fdf8626..296f9262d119 100644 --- a/kernel/rcu/rcu.h +++ b/kernel/rcu/rcu.h @@ -501,6 +501,7 @@ void srcutorture_get_gp_data(enum rcutorture_type test_type, #endif #ifdef CONFIG_TINY_RCU +static inline bool rcu_dynticks_zero_in_eqs(int cpu, int *vp) { return false; } static inline unsigned long rcu_get_gp_seq(void) { return 0; } static inline unsigned long rcu_exp_batches_completed(void) { return 0; } static inline unsigned long @@ -510,6 +511,7 @@ static inline void show_rcu_gp_kthreads(void) { } static inline int rcu_get_gp_kthreads_prio(void) { return 0; } static inline void rcu_fwd_progress_check(unsigned long j) { } #else /* #ifdef CONFIG_TINY_RCU */ +bool rcu_dynticks_zero_in_eqs(int cpu, int *vp); unsigned long rcu_get_gp_seq(void); unsigned long rcu_exp_batches_completed(void); unsigned long srcu_batches_completed(struct srcu_struct *sp); diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h index 4147857007d7..a9e8ecb10860 100644 --- a/kernel/rcu/tasks.h +++ b/kernel/rcu/tasks.h @@ -806,22 +806,38 @@ reset_ipi: /* Callback function for scheduler to check locked-down task. */ static bool trc_inspect_reader(struct task_struct *t, void *arg) { - if (task_curr(t)) - return false; // It is running, so decline to inspect it. + int cpu = task_cpu(t); + bool in_qs = false; + + if (task_curr(t)) { + // If no chance of heavyweight readers, do it the hard way. + if (!IS_ENABLED(CONFIG_TASKS_TRACE_RCU_READ_MB)) + return false; + + // If heavyweight readers are enabled on the remote task, + // we can inspect its state despite its currently running. + // However, we cannot safely change its state. + if (!rcu_dynticks_zero_in_eqs(cpu, &t->trc_reader_nesting)) + return false; // No quiescent state, do it the hard way. + in_qs = true; + } else { + in_qs = likely(!t->trc_reader_nesting); + } // Mark as checked. Because this is called from the grace-period // kthread, also remove the task from the holdout list. t->trc_reader_checked = true; trc_del_holdout(t); - // If the task is in a read-side critical section, set up its - // its state so that it will awaken the grace-period kthread upon - // exit from that critical section. - if (unlikely(t->trc_reader_nesting)) { - atomic_inc(&trc_n_readers_need_end); // One more to wait on. - WARN_ON_ONCE(t->trc_reader_special.b.need_qs); - WRITE_ONCE(t->trc_reader_special.b.need_qs, true); - } + if (in_qs) + return true; // Already in quiescent state, done!!! + + // The task is in a read-side critical section, so set up its + // state so that it will awaken the grace-period kthread upon exit + // from that critical section. + atomic_inc(&trc_n_readers_need_end); // One more to wait on. + WARN_ON_ONCE(t->trc_reader_special.b.need_qs); + WRITE_ONCE(t->trc_reader_special.b.need_qs, true); return true; } diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 0bbcbf398169..573fd78a7bca 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -252,6 +252,7 @@ static void rcu_dynticks_eqs_enter(void) * critical sections, and we also must force ordering with the * next idle sojourn. */ + rcu_dynticks_task_trace_enter(); // Before ->dynticks update! seq = atomic_add_return(RCU_DYNTICK_CTRL_CTR, &rdp->dynticks); // RCU is no longer watching. Better be in extended quiescent state! WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && @@ -278,6 +279,7 @@ static void rcu_dynticks_eqs_exit(void) */ seq = atomic_add_return(RCU_DYNTICK_CTRL_CTR, &rdp->dynticks); // 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_DYNTICK_CTRL_CTR)); if (seq & RCU_DYNTICK_CTRL_MASK) { @@ -350,6 +352,28 @@ static bool rcu_dynticks_in_eqs_since(struct rcu_data *rdp, int snap) } /* + * Return true if the referenced integer is zero while the specified + * CPU remains within a single extended quiescent state. + */ +bool rcu_dynticks_zero_in_eqs(int cpu, int *vp) +{ + struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu); + int snap; + + // If not quiescent, force back to earlier extended quiescent state. + snap = atomic_read(&rdp->dynticks) & ~(RCU_DYNTICK_CTRL_MASK | + RCU_DYNTICK_CTRL_CTR); + + smp_rmb(); // Order ->dynticks and *vp reads. + if (READ_ONCE(*vp)) + return false; // Non-zero, so report failure; + smp_rmb(); // Order *vp read and ->dynticks re-read. + + // If still in the same extended quiescent state, we are good! + return snap == (atomic_read(&rdp->dynticks) & ~RCU_DYNTICK_CTRL_MASK); +} + +/* * Set the special (bottom) bit of the specified CPU so that it * will take special action (such as flushing its TLB) on the * next exit from an extended quiescent state. Returns true if diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h index 9dc2ec021da5..29ba79989802 100644 --- a/kernel/rcu/tree.h +++ b/kernel/rcu/tree.h @@ -454,6 +454,8 @@ static void rcu_bind_gp_kthread(void); static bool rcu_nohz_full_cpu(void); static void rcu_dynticks_task_enter(void); static void rcu_dynticks_task_exit(void); +static void rcu_dynticks_task_trace_enter(void); +static void rcu_dynticks_task_trace_exit(void); /* Forward declarations for tree_stall.h */ static void record_gp_stall_check_time(void); diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 37e02812d18f..4cef7e3bca69 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -2552,3 +2552,21 @@ static void rcu_dynticks_task_exit(void) 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 void rcu_dynticks_task_trace_enter(void) +{ +#ifdef CONFIG_TASKS_RCU_TRACE + if (IS_ENABLED(CONFIG_TASKS_TRACE_RCU_READ_MB)) + current->trc_reader_special.b.need_mb = true; +#endif /* #ifdef CONFIG_TASKS_RCU_TRACE */ +} + +/* Turn off heavyweight RCU tasks trace readers on idle/user exit. */ +static void rcu_dynticks_task_trace_exit(void) +{ +#ifdef CONFIG_TASKS_RCU_TRACE + if (IS_ENABLED(CONFIG_TASKS_TRACE_RCU_READ_MB)) + current->trc_reader_special.b.need_mb = false; +#endif /* #ifdef CONFIG_TASKS_RCU_TRACE */ +} |