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Date: Tue, 26 Mar 2019 16:22:22 -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 08/11] rcu: Organize functions in tree_stall.h
This commit does only code movement, removal of now-unneeded forward
declarations, and addition of comments. It organizes the functions
that implement RCU CPU stall warnings for normal grace periods into
three categories:
1. Control of RCU CPU stall warnings, including computing timeouts.
2. Interaction of stall warnings with grace periods.
3. Actual printing of the RCU CPU stall-warning messages.
Signed-off-by: Paul E. McKenney <paulmck@...ux.ibm.com>
---
kernel/rcu/tree.h | 1 -
kernel/rcu/tree_stall.h | 180 ++++++++++++++++++++++------------------
2 files changed, 97 insertions(+), 84 deletions(-)
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index 49bf3b00bb50..099410dbcbe9 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -442,6 +442,5 @@ static void rcu_dynticks_task_enter(void);
static void rcu_dynticks_task_exit(void);
/* Forward declarations for tree_stall.h */
-static int rcu_print_task_stall(struct rcu_node *rnp);
static void record_gp_stall_check_time(void);
static void check_cpu_stall(struct rcu_data *rdp);
diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
index 19b915380a6f..03ed47883d8a 100644
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@ -7,6 +7,9 @@
* Author: Paul E. McKenney <paulmck@...ux.ibm.com>
*/
+//////////////////////////////////////////////////////////////////////////////
+//
+// Controlling CPU stall warnings, including delay calculation.
/* panic() on RCU Stall sysctl. */
int sysctl_panic_on_rcu_stall __read_mostly;
@@ -17,6 +20,7 @@ int sysctl_panic_on_rcu_stall __read_mostly;
#define RCU_STALL_DELAY_DELTA 0
#endif
+/* Limit-check stall timeouts specified at boottime and runtime. */
int rcu_jiffies_till_stall_check(void)
{
int till_stall_check = READ_ONCE(rcu_cpu_stall_timeout);
@@ -36,6 +40,7 @@ int rcu_jiffies_till_stall_check(void)
}
EXPORT_SYMBOL_GPL(rcu_jiffies_till_stall_check);
+/* Don't do RCU CPU stall warnings during long sysrq printouts. */
void rcu_sysrq_start(void)
{
if (!rcu_cpu_stall_suppress)
@@ -48,6 +53,7 @@ void rcu_sysrq_end(void)
rcu_cpu_stall_suppress = 0;
}
+/* Don't print RCU CPU stall warnings during a kernel panic. */
static int rcu_panic(struct notifier_block *this, unsigned long ev, void *ptr)
{
rcu_cpu_stall_suppress = 1;
@@ -65,6 +71,78 @@ static int __init check_cpu_stall_init(void)
}
early_initcall(check_cpu_stall_init);
+/* If so specified via sysctl, panic, yielding cleaner stall-warning output. */
+static void panic_on_rcu_stall(void)
+{
+ if (sysctl_panic_on_rcu_stall)
+ panic("RCU Stall\n");
+}
+
+/**
+ * rcu_cpu_stall_reset - prevent further stall warnings in current grace period
+ *
+ * Set the stall-warning timeout way off into the future, thus preventing
+ * any RCU CPU stall-warning messages from appearing in the current set of
+ * RCU grace periods.
+ *
+ * The caller must disable hard irqs.
+ */
+void rcu_cpu_stall_reset(void)
+{
+ WRITE_ONCE(rcu_state.jiffies_stall, jiffies + ULONG_MAX / 2);
+}
+
+//////////////////////////////////////////////////////////////////////////////
+//
+// Interaction with RCU grace periods
+
+/* Start of new grace period, so record stall time (and forcing times). */
+static void record_gp_stall_check_time(void)
+{
+ unsigned long j = jiffies;
+ unsigned long j1;
+
+ rcu_state.gp_start = j;
+ j1 = rcu_jiffies_till_stall_check();
+ /* Record ->gp_start before ->jiffies_stall. */
+ smp_store_release(&rcu_state.jiffies_stall, j + j1); /* ^^^ */
+ rcu_state.jiffies_resched = j + j1 / 2;
+ rcu_state.n_force_qs_gpstart = READ_ONCE(rcu_state.n_force_qs);
+}
+
+/* Zero ->ticks_this_gp and snapshot the number of RCU softirq handlers. */
+static void zero_cpu_stall_ticks(struct rcu_data *rdp)
+{
+ rdp->ticks_this_gp = 0;
+ rdp->softirq_snap = kstat_softirqs_cpu(RCU_SOFTIRQ, smp_processor_id());
+ WRITE_ONCE(rdp->last_fqs_resched, jiffies);
+}
+
+/*
+ * If too much time has passed in the current grace period, and if
+ * so configured, go kick the relevant kthreads.
+ */
+static void rcu_stall_kick_kthreads(void)
+{
+ unsigned long j;
+
+ if (!rcu_kick_kthreads)
+ return;
+ j = READ_ONCE(rcu_state.jiffies_kick_kthreads);
+ if (time_after(jiffies, j) && rcu_state.gp_kthread &&
+ (rcu_gp_in_progress() || READ_ONCE(rcu_state.gp_flags))) {
+ WARN_ONCE(1, "Kicking %s grace-period kthread\n",
+ rcu_state.name);
+ rcu_ftrace_dump(DUMP_ALL);
+ wake_up_process(rcu_state.gp_kthread);
+ WRITE_ONCE(rcu_state.jiffies_kick_kthreads, j + HZ);
+ }
+}
+
+//////////////////////////////////////////////////////////////////////////////
+//
+// Printing RCU CPU stall warnings
+
#ifdef CONFIG_PREEMPT
/*
@@ -137,43 +215,6 @@ static int rcu_print_task_stall(struct rcu_node *rnp)
}
#endif /* #else #ifdef CONFIG_PREEMPT */
-static void record_gp_stall_check_time(void)
-{
- unsigned long j = jiffies;
- unsigned long j1;
-
- rcu_state.gp_start = j;
- j1 = rcu_jiffies_till_stall_check();
- /* Record ->gp_start before ->jiffies_stall. */
- smp_store_release(&rcu_state.jiffies_stall, j + j1); /* ^^^ */
- rcu_state.jiffies_resched = j + j1 / 2;
- rcu_state.n_force_qs_gpstart = READ_ONCE(rcu_state.n_force_qs);
-}
-
-/*
- * Complain about starvation of grace-period kthread.
- */
-static void rcu_check_gp_kthread_starvation(void)
-{
- struct task_struct *gpk = rcu_state.gp_kthread;
- unsigned long j;
-
- j = jiffies - READ_ONCE(rcu_state.gp_activity);
- if (j > 2 * HZ) {
- 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),
- 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) {
- pr_err("RCU grace-period kthread stack dump:\n");
- sched_show_task(gpk);
- wake_up_process(gpk);
- }
- }
-}
-
/*
* Dump stacks of all tasks running on stalled CPUs. First try using
* NMIs, but fall back to manual remote stack tracing on architectures
@@ -196,33 +237,6 @@ static void rcu_dump_cpu_stacks(void)
}
}
-/*
- * If too much time has passed in the current grace period, and if
- * so configured, go kick the relevant kthreads.
- */
-static void rcu_stall_kick_kthreads(void)
-{
- unsigned long j;
-
- if (!rcu_kick_kthreads)
- return;
- j = READ_ONCE(rcu_state.jiffies_kick_kthreads);
- if (time_after(jiffies, j) && rcu_state.gp_kthread &&
- (rcu_gp_in_progress() || READ_ONCE(rcu_state.gp_flags))) {
- WARN_ONCE(1, "Kicking %s grace-period kthread\n",
- rcu_state.name);
- rcu_ftrace_dump(DUMP_ALL);
- wake_up_process(rcu_state.gp_kthread);
- WRITE_ONCE(rcu_state.jiffies_kick_kthreads, j + HZ);
- }
-}
-
-static void panic_on_rcu_stall(void)
-{
- if (sysctl_panic_on_rcu_stall)
- panic("RCU Stall\n");
-}
-
#ifdef CONFIG_RCU_FAST_NO_HZ
static void print_cpu_stall_fast_no_hz(char *cp, int cpu)
@@ -295,12 +309,26 @@ static void print_cpu_stall_info(int cpu)
fast_no_hz);
}
-/* Zero ->ticks_this_gp and snapshot the number of RCU softirq handlers. */
-static void zero_cpu_stall_ticks(struct rcu_data *rdp)
+/* Complain about starvation of grace-period kthread. */
+static void rcu_check_gp_kthread_starvation(void)
{
- rdp->ticks_this_gp = 0;
- rdp->softirq_snap = kstat_softirqs_cpu(RCU_SOFTIRQ, smp_processor_id());
- WRITE_ONCE(rdp->last_fqs_resched, jiffies);
+ struct task_struct *gpk = rcu_state.gp_kthread;
+ unsigned long j;
+
+ j = jiffies - READ_ONCE(rcu_state.gp_activity);
+ if (j > 2 * HZ) {
+ 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),
+ 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) {
+ pr_err("RCU grace-period kthread stack dump:\n");
+ sched_show_task(gpk);
+ wake_up_process(gpk);
+ }
+ }
}
static void print_other_cpu_stall(unsigned long gp_seq)
@@ -488,17 +516,3 @@ static void check_cpu_stall(struct rcu_data *rdp)
print_other_cpu_stall(gs2);
}
}
-
-/**
- * rcu_cpu_stall_reset - prevent further stall warnings in current grace period
- *
- * Set the stall-warning timeout way off into the future, thus preventing
- * any RCU CPU stall-warning messages from appearing in the current set of
- * RCU grace periods.
- *
- * The caller must disable hard irqs.
- */
-void rcu_cpu_stall_reset(void)
-{
- WRITE_ONCE(rcu_state.jiffies_stall, jiffies + ULONG_MAX / 2);
-}
--
2.17.1
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