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rcu: Move forward-progress checkers into tree_stall.h
This commit further consolidates stall-warning functionality by moving forward-progress checkers into kernel/rcu/tree_stall.h, updating a comment or two while in the area. More specifically, this commit moves show_rcu_gp_kthreads(), rcu_check_gp_start_stall(), rcu_fwd_progress_check(), sysrq_rcu, sysrq_show_rcu(), sysrq_rcudump_op, and rcu_sysrq_init() from kernel/rcu/tree.c to kernel/rcu/tree_stall.h. Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
This commit is contained in:
Paul E. McKenney
parent
7ac1907c9e
commit
b51bcbbf16
3 changed files with 173 additions and 166 deletions
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@ -102,9 +102,6 @@ int rcu_num_lvls __read_mostly = RCU_NUM_LVLS;
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/* Number of rcu_nodes at specified level. */
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int num_rcu_lvl[] = NUM_RCU_LVL_INIT;
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int rcu_num_nodes __read_mostly = NUM_RCU_NODES; /* Total # rcu_nodes in use. */
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/* Commandeer a sysrq key to dump RCU's tree. */
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static bool sysrq_rcu;
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module_param(sysrq_rcu, bool, 0444);
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/*
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* The rcu_scheduler_active variable is initialized to the value
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@ -510,74 +507,6 @@ static const char *gp_state_getname(short gs)
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return gp_state_names[gs];
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}
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/*
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* Show the state of the grace-period kthreads.
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*/
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void show_rcu_gp_kthreads(void)
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{
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int cpu;
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unsigned long j;
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unsigned long ja;
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unsigned long jr;
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unsigned long jw;
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struct rcu_data *rdp;
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struct rcu_node *rnp;
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j = jiffies;
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ja = j - READ_ONCE(rcu_state.gp_activity);
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jr = j - READ_ONCE(rcu_state.gp_req_activity);
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jw = j - READ_ONCE(rcu_state.gp_wake_time);
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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",
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rcu_state.name, gp_state_getname(rcu_state.gp_state),
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rcu_state.gp_state,
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rcu_state.gp_kthread ? rcu_state.gp_kthread->state : 0x1ffffL,
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ja, jr, jw, (long)READ_ONCE(rcu_state.gp_wake_seq),
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(long)READ_ONCE(rcu_state.gp_seq),
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(long)READ_ONCE(rcu_get_root()->gp_seq_needed),
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READ_ONCE(rcu_state.gp_flags));
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rcu_for_each_node_breadth_first(rnp) {
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if (ULONG_CMP_GE(rcu_state.gp_seq, rnp->gp_seq_needed))
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continue;
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pr_info("\trcu_node %d:%d ->gp_seq %ld ->gp_seq_needed %ld\n",
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rnp->grplo, rnp->grphi, (long)rnp->gp_seq,
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(long)rnp->gp_seq_needed);
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if (!rcu_is_leaf_node(rnp))
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continue;
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for_each_leaf_node_possible_cpu(rnp, cpu) {
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rdp = per_cpu_ptr(&rcu_data, cpu);
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if (rdp->gpwrap ||
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ULONG_CMP_GE(rcu_state.gp_seq,
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rdp->gp_seq_needed))
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continue;
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pr_info("\tcpu %d ->gp_seq_needed %ld\n",
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cpu, (long)rdp->gp_seq_needed);
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}
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}
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/* sched_show_task(rcu_state.gp_kthread); */
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}
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EXPORT_SYMBOL_GPL(show_rcu_gp_kthreads);
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/* Dump grace-period-request information due to commandeered sysrq. */
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static void sysrq_show_rcu(int key)
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{
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show_rcu_gp_kthreads();
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}
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static struct sysrq_key_op sysrq_rcudump_op = {
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.handler = sysrq_show_rcu,
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.help_msg = "show-rcu(y)",
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.action_msg = "Show RCU tree",
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.enable_mask = SYSRQ_ENABLE_DUMP,
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};
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static int __init rcu_sysrq_init(void)
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{
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if (sysrq_rcu)
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return register_sysrq_key('y', &sysrq_rcudump_op);
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return 0;
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}
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early_initcall(rcu_sysrq_init);
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/*
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* Send along grace-period-related data for rcutorture diagnostics.
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*/
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@ -2323,101 +2252,6 @@ void rcu_force_quiescent_state(void)
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}
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EXPORT_SYMBOL_GPL(rcu_force_quiescent_state);
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/*
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* This function checks for grace-period requests that fail to motivate
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* RCU to come out of its idle mode.
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*/
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void
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rcu_check_gp_start_stall(struct rcu_node *rnp, struct rcu_data *rdp,
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const unsigned long gpssdelay)
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{
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unsigned long flags;
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unsigned long j;
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struct rcu_node *rnp_root = rcu_get_root();
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static atomic_t warned = ATOMIC_INIT(0);
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if (!IS_ENABLED(CONFIG_PROVE_RCU) || rcu_gp_in_progress() ||
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ULONG_CMP_GE(rnp_root->gp_seq, rnp_root->gp_seq_needed))
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return;
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j = jiffies; /* Expensive access, and in common case don't get here. */
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if (time_before(j, READ_ONCE(rcu_state.gp_req_activity) + gpssdelay) ||
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time_before(j, READ_ONCE(rcu_state.gp_activity) + gpssdelay) ||
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atomic_read(&warned))
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return;
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raw_spin_lock_irqsave_rcu_node(rnp, flags);
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j = jiffies;
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if (rcu_gp_in_progress() ||
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ULONG_CMP_GE(rnp_root->gp_seq, rnp_root->gp_seq_needed) ||
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time_before(j, READ_ONCE(rcu_state.gp_req_activity) + gpssdelay) ||
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time_before(j, READ_ONCE(rcu_state.gp_activity) + gpssdelay) ||
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atomic_read(&warned)) {
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raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
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return;
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}
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/* Hold onto the leaf lock to make others see warned==1. */
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if (rnp_root != rnp)
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raw_spin_lock_rcu_node(rnp_root); /* irqs already disabled. */
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j = jiffies;
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if (rcu_gp_in_progress() ||
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ULONG_CMP_GE(rnp_root->gp_seq, rnp_root->gp_seq_needed) ||
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time_before(j, rcu_state.gp_req_activity + gpssdelay) ||
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time_before(j, rcu_state.gp_activity + gpssdelay) ||
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atomic_xchg(&warned, 1)) {
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raw_spin_unlock_rcu_node(rnp_root); /* irqs remain disabled. */
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raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
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return;
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}
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WARN_ON(1);
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if (rnp_root != rnp)
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raw_spin_unlock_rcu_node(rnp_root);
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raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
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show_rcu_gp_kthreads();
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}
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/*
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* Do a forward-progress check for rcutorture. This is normally invoked
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* due to an OOM event. The argument "j" gives the time period during
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* which rcutorture would like progress to have been made.
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*/
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void rcu_fwd_progress_check(unsigned long j)
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{
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unsigned long cbs;
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int cpu;
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unsigned long max_cbs = 0;
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int max_cpu = -1;
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struct rcu_data *rdp;
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if (rcu_gp_in_progress()) {
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pr_info("%s: GP age %lu jiffies\n",
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__func__, jiffies - rcu_state.gp_start);
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show_rcu_gp_kthreads();
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} else {
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pr_info("%s: Last GP end %lu jiffies ago\n",
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__func__, jiffies - rcu_state.gp_end);
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preempt_disable();
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rdp = this_cpu_ptr(&rcu_data);
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rcu_check_gp_start_stall(rdp->mynode, rdp, j);
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preempt_enable();
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}
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for_each_possible_cpu(cpu) {
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cbs = rcu_get_n_cbs_cpu(cpu);
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if (!cbs)
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continue;
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if (max_cpu < 0)
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pr_info("%s: callbacks", __func__);
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pr_cont(" %d: %lu", cpu, cbs);
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if (cbs <= max_cbs)
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continue;
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max_cbs = cbs;
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max_cpu = cpu;
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}
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if (max_cpu >= 0)
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pr_cont("\n");
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}
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EXPORT_SYMBOL_GPL(rcu_fwd_progress_check);
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/* Perform RCU core processing work for the current CPU. */
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static __latent_entropy void rcu_core(struct softirq_action *unused)
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{
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@ -445,3 +445,5 @@ static void rcu_dynticks_task_exit(void);
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static void record_gp_stall_check_time(void);
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static void rcu_iw_handler(struct irq_work *iwp);
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static void check_cpu_stall(struct rcu_data *rdp);
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static void rcu_check_gp_start_stall(struct rcu_node *rnp, struct rcu_data *rdp,
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const unsigned long gpssdelay);
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@ -536,3 +536,174 @@ static void check_cpu_stall(struct rcu_data *rdp)
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print_other_cpu_stall(gs2);
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}
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}
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//////////////////////////////////////////////////////////////////////////////
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//
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// RCU forward-progress mechanisms, including of callback invocation.
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/*
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* Show the state of the grace-period kthreads.
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*/
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void show_rcu_gp_kthreads(void)
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{
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int cpu;
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unsigned long j;
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unsigned long ja;
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unsigned long jr;
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unsigned long jw;
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struct rcu_data *rdp;
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struct rcu_node *rnp;
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j = jiffies;
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ja = j - READ_ONCE(rcu_state.gp_activity);
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jr = j - READ_ONCE(rcu_state.gp_req_activity);
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jw = j - READ_ONCE(rcu_state.gp_wake_time);
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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",
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rcu_state.name, gp_state_getname(rcu_state.gp_state),
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rcu_state.gp_state,
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rcu_state.gp_kthread ? rcu_state.gp_kthread->state : 0x1ffffL,
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ja, jr, jw, (long)READ_ONCE(rcu_state.gp_wake_seq),
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(long)READ_ONCE(rcu_state.gp_seq),
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(long)READ_ONCE(rcu_get_root()->gp_seq_needed),
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READ_ONCE(rcu_state.gp_flags));
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rcu_for_each_node_breadth_first(rnp) {
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if (ULONG_CMP_GE(rcu_state.gp_seq, rnp->gp_seq_needed))
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continue;
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pr_info("\trcu_node %d:%d ->gp_seq %ld ->gp_seq_needed %ld\n",
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rnp->grplo, rnp->grphi, (long)rnp->gp_seq,
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(long)rnp->gp_seq_needed);
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if (!rcu_is_leaf_node(rnp))
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continue;
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for_each_leaf_node_possible_cpu(rnp, cpu) {
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rdp = per_cpu_ptr(&rcu_data, cpu);
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if (rdp->gpwrap ||
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ULONG_CMP_GE(rcu_state.gp_seq,
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rdp->gp_seq_needed))
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continue;
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pr_info("\tcpu %d ->gp_seq_needed %ld\n",
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cpu, (long)rdp->gp_seq_needed);
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}
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}
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/* sched_show_task(rcu_state.gp_kthread); */
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}
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EXPORT_SYMBOL_GPL(show_rcu_gp_kthreads);
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/*
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* This function checks for grace-period requests that fail to motivate
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* RCU to come out of its idle mode.
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*/
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static void rcu_check_gp_start_stall(struct rcu_node *rnp, struct rcu_data *rdp,
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const unsigned long gpssdelay)
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{
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unsigned long flags;
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unsigned long j;
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struct rcu_node *rnp_root = rcu_get_root();
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static atomic_t warned = ATOMIC_INIT(0);
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if (!IS_ENABLED(CONFIG_PROVE_RCU) || rcu_gp_in_progress() ||
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ULONG_CMP_GE(rnp_root->gp_seq, rnp_root->gp_seq_needed))
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return;
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j = jiffies; /* Expensive access, and in common case don't get here. */
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if (time_before(j, READ_ONCE(rcu_state.gp_req_activity) + gpssdelay) ||
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time_before(j, READ_ONCE(rcu_state.gp_activity) + gpssdelay) ||
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atomic_read(&warned))
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return;
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raw_spin_lock_irqsave_rcu_node(rnp, flags);
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j = jiffies;
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if (rcu_gp_in_progress() ||
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ULONG_CMP_GE(rnp_root->gp_seq, rnp_root->gp_seq_needed) ||
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time_before(j, READ_ONCE(rcu_state.gp_req_activity) + gpssdelay) ||
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time_before(j, READ_ONCE(rcu_state.gp_activity) + gpssdelay) ||
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atomic_read(&warned)) {
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raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
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return;
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}
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/* Hold onto the leaf lock to make others see warned==1. */
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if (rnp_root != rnp)
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raw_spin_lock_rcu_node(rnp_root); /* irqs already disabled. */
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j = jiffies;
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if (rcu_gp_in_progress() ||
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ULONG_CMP_GE(rnp_root->gp_seq, rnp_root->gp_seq_needed) ||
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time_before(j, rcu_state.gp_req_activity + gpssdelay) ||
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time_before(j, rcu_state.gp_activity + gpssdelay) ||
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atomic_xchg(&warned, 1)) {
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raw_spin_unlock_rcu_node(rnp_root); /* irqs remain disabled. */
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raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
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return;
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}
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WARN_ON(1);
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if (rnp_root != rnp)
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raw_spin_unlock_rcu_node(rnp_root);
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raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
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show_rcu_gp_kthreads();
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}
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/*
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* Do a forward-progress check for rcutorture. This is normally invoked
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* due to an OOM event. The argument "j" gives the time period during
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* which rcutorture would like progress to have been made.
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*/
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void rcu_fwd_progress_check(unsigned long j)
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{
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unsigned long cbs;
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int cpu;
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unsigned long max_cbs = 0;
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int max_cpu = -1;
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struct rcu_data *rdp;
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if (rcu_gp_in_progress()) {
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pr_info("%s: GP age %lu jiffies\n",
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__func__, jiffies - rcu_state.gp_start);
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show_rcu_gp_kthreads();
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} else {
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pr_info("%s: Last GP end %lu jiffies ago\n",
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__func__, jiffies - rcu_state.gp_end);
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preempt_disable();
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rdp = this_cpu_ptr(&rcu_data);
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rcu_check_gp_start_stall(rdp->mynode, rdp, j);
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preempt_enable();
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}
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for_each_possible_cpu(cpu) {
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cbs = rcu_get_n_cbs_cpu(cpu);
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if (!cbs)
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continue;
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if (max_cpu < 0)
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pr_info("%s: callbacks", __func__);
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pr_cont(" %d: %lu", cpu, cbs);
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if (cbs <= max_cbs)
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continue;
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max_cbs = cbs;
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max_cpu = cpu;
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}
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if (max_cpu >= 0)
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pr_cont("\n");
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}
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EXPORT_SYMBOL_GPL(rcu_fwd_progress_check);
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/* Commandeer a sysrq key to dump RCU's tree. */
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static bool sysrq_rcu;
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module_param(sysrq_rcu, bool, 0444);
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/* Dump grace-period-request information due to commandeered sysrq. */
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static void sysrq_show_rcu(int key)
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{
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show_rcu_gp_kthreads();
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}
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static struct sysrq_key_op sysrq_rcudump_op = {
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.handler = sysrq_show_rcu,
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.help_msg = "show-rcu(y)",
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.action_msg = "Show RCU tree",
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.enable_mask = SYSRQ_ENABLE_DUMP,
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};
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static int __init rcu_sysrq_init(void)
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{
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if (sysrq_rcu)
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return register_sysrq_key('y', &sysrq_rcudump_op);
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return 0;
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}
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early_initcall(rcu_sysrq_init);
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