diff options
Diffstat (limited to 'kernel/rcu/tree.c')
| -rw-r--r-- | kernel/rcu/tree.c | 102 |
1 files changed, 72 insertions, 30 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index e53a586b397b..1c4add096078 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -62,6 +62,7 @@ #include <linux/suspend.h> #include <linux/ftrace.h> #include <linux/tick.h> +#include <linux/sysrq.h> #include "tree.h" #include "rcu.h" @@ -115,6 +116,9 @@ int num_rcu_lvl[] = NUM_RCU_LVL_INIT; int rcu_num_nodes __read_mostly = NUM_RCU_NODES; /* Total # rcu_nodes in use. */ /* panic() on RCU Stall sysctl. */ int sysctl_panic_on_rcu_stall __read_mostly; +/* Commandeer a sysrq key to dump RCU's tree. */ +static bool sysrq_rcu; +module_param(sysrq_rcu, bool, 0444); /* * The rcu_scheduler_active variable is initialized to the value @@ -503,6 +507,14 @@ unsigned long rcu_exp_batches_completed(void) EXPORT_SYMBOL_GPL(rcu_exp_batches_completed); /* + * Return the root node of the rcu_state structure. + */ +static struct rcu_node *rcu_get_root(void) +{ + return &rcu_state.node[0]; +} + +/* * Convert a ->gp_state value to a character string. */ static const char *gp_state_getname(short gs) @@ -519,19 +531,30 @@ 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 - READ_ONCE(rcu_state.gp_activity); - pr_info("%s: wait state: %s(%d) ->state: %#lx delta ->gp_activity %ld\n", + 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->state, j); + 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 %lu ->gp_seq_needed %lu\n", - rnp->grplo, rnp->grphi, rnp->gp_seq, - rnp->gp_seq_needed); + 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) { @@ -540,14 +563,35 @@ void show_rcu_gp_kthreads(void) ULONG_CMP_GE(rcu_state.gp_seq, rdp->gp_seq_needed)) continue; - pr_info("\tcpu %d ->gp_seq_needed %lu\n", - cpu, rdp->gp_seq_needed); + 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); +/* 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); + /* * Send along grace-period-related data for rcutorture diagnostics. */ @@ -566,14 +610,6 @@ void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags, EXPORT_SYMBOL_GPL(rcutorture_get_gp_data); /* - * Return the root node of the rcu_state structure. - */ -static struct rcu_node *rcu_get_root(void) -{ - return &rcu_state.node[0]; -} - -/* * Enter an RCU extended quiescent state, which can be either the * idle loop or adaptive-tickless usermode execution. * @@ -1169,7 +1205,7 @@ static void rcu_check_gp_kthread_starvation(void) pr_err("%s kthread starved for %ld jiffies! g%ld f%#x %s(%d) ->state=%#lx ->cpu=%d\n", rcu_state.name, j, (long)rcu_seq_current(&rcu_state.gp_seq), - rcu_state.gp_flags, + READ_ONCE(rcu_state.gp_flags), gp_state_getname(rcu_state.gp_state), rcu_state.gp_state, gpk ? gpk->state : ~0, gpk ? task_cpu(gpk) : -1); if (gpk) { @@ -1545,17 +1581,28 @@ static bool rcu_future_gp_cleanup(struct rcu_node *rnp) } /* - * Awaken the grace-period kthread. Don't do a self-awaken, and don't - * bother awakening when there is nothing for the grace-period kthread - * to do (as in several CPUs raced to awaken, and we lost), and finally - * don't try to awaken a kthread that has not yet been created. + * Awaken the grace-period kthread. Don't do a self-awaken (unless in + * an interrupt or softirq handler), and don't bother awakening when there + * is nothing for the grace-period kthread to do (as in several CPUs raced + * to awaken, and we lost), and finally don't try to awaken a kthread that + * has not yet been created. If all those checks are passed, track some + * debug information and awaken. + * + * So why do the self-wakeup when in an interrupt or softirq handler + * in the grace-period kthread's context? Because the kthread might have + * been interrupted just as it was going to sleep, and just after the final + * pre-sleep check of the awaken condition. In this case, a wakeup really + * is required, and is therefore supplied. */ static void rcu_gp_kthread_wake(void) { - if (current == rcu_state.gp_kthread || + if ((current == rcu_state.gp_kthread && + !in_interrupt() && !in_serving_softirq()) || !READ_ONCE(rcu_state.gp_flags) || !rcu_state.gp_kthread) return; + WRITE_ONCE(rcu_state.gp_wake_time, jiffies); + WRITE_ONCE(rcu_state.gp_wake_seq, READ_ONCE(rcu_state.gp_seq)); swake_up_one(&rcu_state.gp_wq); } @@ -1699,7 +1746,7 @@ static bool __note_gp_changes(struct rcu_node *rnp, struct rcu_data *rdp) zero_cpu_stall_ticks(rdp); } rdp->gp_seq = rnp->gp_seq; /* Remember new grace-period state. */ - if (ULONG_CMP_GE(rnp->gp_seq_needed, rdp->gp_seq_needed) || rdp->gpwrap) + if (ULONG_CMP_LT(rdp->gp_seq_needed, rnp->gp_seq_needed) || rdp->gpwrap) rdp->gp_seq_needed = rnp->gp_seq_needed; WRITE_ONCE(rdp->gpwrap, false); rcu_gpnum_ovf(rnp, rdp); @@ -1927,7 +1974,7 @@ static void rcu_gp_fqs_loop(void) if (!ret) { rcu_state.jiffies_force_qs = jiffies + j; WRITE_ONCE(rcu_state.jiffies_kick_kthreads, - jiffies + 3 * j); + jiffies + (j ? 3 * j : 2)); } trace_rcu_grace_period(rcu_state.name, READ_ONCE(rcu_state.gp_seq), @@ -2646,16 +2693,11 @@ rcu_check_gp_start_stall(struct rcu_node *rnp, struct rcu_data *rdp, raw_spin_unlock_irqrestore_rcu_node(rnp, flags); return; } - pr_alert("%s: g%ld->%ld gar:%lu ga:%lu f%#x gs:%d %s->state:%#lx\n", - __func__, (long)READ_ONCE(rcu_state.gp_seq), - (long)READ_ONCE(rnp_root->gp_seq_needed), - j - rcu_state.gp_req_activity, j - rcu_state.gp_activity, - rcu_state.gp_flags, rcu_state.gp_state, rcu_state.name, - rcu_state.gp_kthread ? rcu_state.gp_kthread->state : 0x1ffffL); 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(); } /* |