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Message-Id: <20190326232225.21332-10-paulmck@linux.ibm.com>
Date: Tue, 26 Mar 2019 16:22:24 -0700
From: "Paul E. McKenney" <paulmck@...ux.ibm.com>
To: rcu@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, mingo@...nel.org,
jiangshanlai@...il.com, dipankar@...ibm.com,
akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com,
fweisbec@...il.com, oleg@...hat.com, joel@...lfernandes.org,
"Paul E. McKenney" <paulmck@...ux.ibm.com>
Subject: [PATCH tip/core/rcu 10/11] 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@...ux.ibm.com>
---
kernel/rcu/tree.c | 166 --------------------------------------
kernel/rcu/tree.h | 2 +
kernel/rcu/tree_stall.h | 171 ++++++++++++++++++++++++++++++++++++++++
3 files changed, 173 insertions(+), 166 deletions(-)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 929531ed168c..4cb1ebd93b0c 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -102,9 +102,6 @@ int rcu_num_lvls __read_mostly = RCU_NUM_LVLS;
/* Number of rcu_nodes at specified level. */
int num_rcu_lvl[] = NUM_RCU_LVL_INIT;
int rcu_num_nodes __read_mostly = NUM_RCU_NODES; /* Total # rcu_nodes in use. */
-/* 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
@@ -510,74 +507,6 @@ static const char *gp_state_getname(short gs)
return gp_state_names[gs];
}
-/*
- * 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);
-
-/* 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.
*/
@@ -2323,101 +2252,6 @@ void rcu_force_quiescent_state(void)
}
EXPORT_SYMBOL_GPL(rcu_force_quiescent_state);
-/*
- * This function checks for grace-period requests that fail to motivate
- * RCU to come out of its idle mode.
- */
-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);
-
/* Perform RCU core processing work for the current CPU. */
static __latent_entropy void rcu_core(struct softirq_action *unused)
{
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index f882ce3ca5a5..e253d11af3c4 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -445,3 +445,5 @@ static void rcu_dynticks_task_exit(void);
static void record_gp_stall_check_time(void);
static void rcu_iw_handler(struct irq_work *iwp);
static void check_cpu_stall(struct rcu_data *rdp);
+static void rcu_check_gp_start_stall(struct rcu_node *rnp, struct rcu_data *rdp,
+ const unsigned long gpssdelay);
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);
--
2.17.1
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