diff options
Diffstat (limited to 'kernel/rcu/tree_stall.h')
| -rw-r--r-- | kernel/rcu/tree_stall.h | 171 |
1 files changed, 171 insertions, 0 deletions
diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h index 526e223e41ce..9e3db08d02bc 100644 --- a/kernel/rcu/tree_stall.h +++ b/kernel/rcu/tree_stall.h @@ -536,3 +536,174 @@ static void check_cpu_stall(struct rcu_data *rdp) print_other_cpu_stall(gs2); } } + +////////////////////////////////////////////////////////////////////////////// +// +// RCU forward-progress mechanisms, including of callback invocation. + + +/* + * Show the state of the grace-period kthreads. + */ +void show_rcu_gp_kthreads(void) +{ + int cpu; + unsigned long j; + unsigned long ja; + unsigned long jr; + unsigned long jw; + struct rcu_data *rdp; + struct rcu_node *rnp; + + j = jiffies; + ja = j - READ_ONCE(rcu_state.gp_activity); + jr = j - READ_ONCE(rcu_state.gp_req_activity); + jw = j - READ_ONCE(rcu_state.gp_wake_time); + pr_info("%s: wait state: %s(%d) ->state: %#lx delta ->gp_activity %lu ->gp_req_activity %lu ->gp_wake_time %lu ->gp_wake_seq %ld ->gp_seq %ld ->gp_seq_needed %ld ->gp_flags %#x\n", + rcu_state.name, gp_state_getname(rcu_state.gp_state), + rcu_state.gp_state, + rcu_state.gp_kthread ? rcu_state.gp_kthread->state : 0x1ffffL, + ja, jr, jw, (long)READ_ONCE(rcu_state.gp_wake_seq), + (long)READ_ONCE(rcu_state.gp_seq), + (long)READ_ONCE(rcu_get_root()->gp_seq_needed), + READ_ONCE(rcu_state.gp_flags)); + rcu_for_each_node_breadth_first(rnp) { + if (ULONG_CMP_GE(rcu_state.gp_seq, rnp->gp_seq_needed)) + continue; + pr_info("\trcu_node %d:%d ->gp_seq %ld ->gp_seq_needed %ld\n", + rnp->grplo, rnp->grphi, (long)rnp->gp_seq, + (long)rnp->gp_seq_needed); + if (!rcu_is_leaf_node(rnp)) + continue; + for_each_leaf_node_possible_cpu(rnp, cpu) { + rdp = per_cpu_ptr(&rcu_data, cpu); + if (rdp->gpwrap || + ULONG_CMP_GE(rcu_state.gp_seq, + rdp->gp_seq_needed)) + continue; + pr_info("\tcpu %d ->gp_seq_needed %ld\n", + cpu, (long)rdp->gp_seq_needed); + } + } + /* sched_show_task(rcu_state.gp_kthread); */ +} +EXPORT_SYMBOL_GPL(show_rcu_gp_kthreads); + +/* + * This function checks for grace-period requests that fail to motivate + * RCU to come out of its idle mode. + */ +static void rcu_check_gp_start_stall(struct rcu_node *rnp, struct rcu_data *rdp, + const unsigned long gpssdelay) +{ + unsigned long flags; + unsigned long j; + struct rcu_node *rnp_root = rcu_get_root(); + static atomic_t warned = ATOMIC_INIT(0); + + if (!IS_ENABLED(CONFIG_PROVE_RCU) || rcu_gp_in_progress() || + ULONG_CMP_GE(rnp_root->gp_seq, rnp_root->gp_seq_needed)) + return; + j = jiffies; /* Expensive access, and in common case don't get here. */ + if (time_before(j, READ_ONCE(rcu_state.gp_req_activity) + gpssdelay) || + time_before(j, READ_ONCE(rcu_state.gp_activity) + gpssdelay) || + atomic_read(&warned)) + return; + + raw_spin_lock_irqsave_rcu_node(rnp, flags); + j = jiffies; + if (rcu_gp_in_progress() || + ULONG_CMP_GE(rnp_root->gp_seq, rnp_root->gp_seq_needed) || + time_before(j, READ_ONCE(rcu_state.gp_req_activity) + gpssdelay) || + time_before(j, READ_ONCE(rcu_state.gp_activity) + gpssdelay) || + atomic_read(&warned)) { + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + return; + } + /* Hold onto the leaf lock to make others see warned==1. */ + + if (rnp_root != rnp) + raw_spin_lock_rcu_node(rnp_root); /* irqs already disabled. */ + j = jiffies; + if (rcu_gp_in_progress() || + ULONG_CMP_GE(rnp_root->gp_seq, rnp_root->gp_seq_needed) || + time_before(j, rcu_state.gp_req_activity + gpssdelay) || + time_before(j, rcu_state.gp_activity + gpssdelay) || + atomic_xchg(&warned, 1)) { + raw_spin_unlock_rcu_node(rnp_root); /* irqs remain disabled. */ + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + return; + } + WARN_ON(1); + if (rnp_root != rnp) + raw_spin_unlock_rcu_node(rnp_root); + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + show_rcu_gp_kthreads(); +} + +/* + * Do a forward-progress check for rcutorture. This is normally invoked + * due to an OOM event. The argument "j" gives the time period during + * which rcutorture would like progress to have been made. + */ +void rcu_fwd_progress_check(unsigned long j) +{ + unsigned long cbs; + int cpu; + unsigned long max_cbs = 0; + int max_cpu = -1; + struct rcu_data *rdp; + + if (rcu_gp_in_progress()) { + pr_info("%s: GP age %lu jiffies\n", + __func__, jiffies - rcu_state.gp_start); + show_rcu_gp_kthreads(); + } else { + pr_info("%s: Last GP end %lu jiffies ago\n", + __func__, jiffies - rcu_state.gp_end); + preempt_disable(); + rdp = this_cpu_ptr(&rcu_data); + rcu_check_gp_start_stall(rdp->mynode, rdp, j); + preempt_enable(); + } + for_each_possible_cpu(cpu) { + cbs = rcu_get_n_cbs_cpu(cpu); + if (!cbs) + continue; + if (max_cpu < 0) + pr_info("%s: callbacks", __func__); + pr_cont(" %d: %lu", cpu, cbs); + if (cbs <= max_cbs) + continue; + max_cbs = cbs; + max_cpu = cpu; + } + if (max_cpu >= 0) + pr_cont("\n"); +} +EXPORT_SYMBOL_GPL(rcu_fwd_progress_check); + +/* Commandeer a sysrq key to dump RCU's tree. */ +static bool sysrq_rcu; +module_param(sysrq_rcu, bool, 0444); + +/* Dump grace-period-request information due to commandeered sysrq. */ +static void sysrq_show_rcu(int key) +{ + show_rcu_gp_kthreads(); +} + +static struct sysrq_key_op sysrq_rcudump_op = { + .handler = sysrq_show_rcu, + .help_msg = "show-rcu(y)", + .action_msg = "Show RCU tree", + .enable_mask = SYSRQ_ENABLE_DUMP, +}; + +static int __init rcu_sysrq_init(void) +{ + if (sysrq_rcu) + return register_sysrq_key('y', &sysrq_rcudump_op); + return 0; +} +early_initcall(rcu_sysrq_init); |