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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2010-08-10 14:28:53 -0700
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2010-08-20 09:00:12 -0700
commit53d84e004d5e8c018be395c4330dc72fd60bd13e (patch)
tree6d5b265442ac42c7cc73147b0de0d029644e312b
parent8cdd32a918350430483751feaae1c19cef816f69 (diff)
downloadlinux-53d84e004d5e8c018be395c4330dc72fd60bd13e.tar.bz2
rcu: permit suppressing current grace period's CPU stall warnings
When using a kernel debugger, a long sojourn in the debugger can get you lots of RCU CPU stall warnings once you resume. This might not be helpful, especially if you are using the system console. This patch therefore allows RCU CPU stall warnings to be suppressed, but only for the duration of the current set of grace periods. This differs from Jason's original patch in that it adds support for tiny RCU and preemptible RCU, and uses a slightly different method for suppressing the RCU CPU stall warning messages. Signed-off-by: Jason Wessel <jason.wessel@windriver.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Tested-by: Jason Wessel <jason.wessel@windriver.com>
-rw-r--r--include/linux/rcutiny.h4
-rw-r--r--include/linux/rcutree.h1
-rw-r--r--kernel/rcutree.c20
-rw-r--r--kernel/rcutree.h1
-rw-r--r--kernel/rcutree_plugin.h18
5 files changed, 44 insertions, 0 deletions
diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h
index 4cc5eba41616..3fa179784e18 100644
--- a/include/linux/rcutiny.h
+++ b/include/linux/rcutiny.h
@@ -178,6 +178,10 @@ static inline void rcu_sched_force_quiescent_state(void)
{
}
+static inline void rcu_cpu_stall_reset(void)
+{
+}
+
#ifdef CONFIG_DEBUG_LOCK_ALLOC
extern int rcu_scheduler_active __read_mostly;
diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h
index c13b85dd22bc..0726809497ba 100644
--- a/include/linux/rcutree.h
+++ b/include/linux/rcutree.h
@@ -36,6 +36,7 @@ extern void rcu_sched_qs(int cpu);
extern void rcu_bh_qs(int cpu);
extern void rcu_note_context_switch(int cpu);
extern int rcu_needs_cpu(int cpu);
+extern void rcu_cpu_stall_reset(void);
#ifdef CONFIG_TREE_PREEMPT_RCU
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index ff214118e4b8..42140a860bb9 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -565,6 +565,22 @@ static int rcu_panic(struct notifier_block *this, unsigned long ev, void *ptr)
return NOTIFY_DONE;
}
+/**
+ * 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)
+{
+ rcu_sched_state.jiffies_stall = jiffies + ULONG_MAX / 2;
+ rcu_bh_state.jiffies_stall = jiffies + ULONG_MAX / 2;
+ rcu_preempt_stall_reset();
+}
+
static struct notifier_block rcu_panic_block = {
.notifier_call = rcu_panic,
};
@@ -584,6 +600,10 @@ static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp)
{
}
+void rcu_cpu_stall_reset(void)
+{
+}
+
static void __init check_cpu_stall_init(void)
{
}
diff --git a/kernel/rcutree.h b/kernel/rcutree.h
index bb4d08695c45..7abd439a7573 100644
--- a/kernel/rcutree.h
+++ b/kernel/rcutree.h
@@ -372,6 +372,7 @@ static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp,
#ifdef CONFIG_RCU_CPU_STALL_DETECTOR
static void rcu_print_detail_task_stall(struct rcu_state *rsp);
static void rcu_print_task_stall(struct rcu_node *rnp);
+static void rcu_preempt_stall_reset(void);
#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp);
#ifdef CONFIG_HOTPLUG_CPU
diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index 63bb7714fdeb..561410f70d4a 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -417,6 +417,16 @@ static void rcu_print_task_stall(struct rcu_node *rnp)
}
}
+/*
+ * Suppress preemptible RCU's CPU stall warnings by pushing the
+ * time of the next stall-warning message comfortably far into the
+ * future.
+ */
+static void rcu_preempt_stall_reset(void)
+{
+ rcu_preempt_state.jiffies_stall = jiffies + ULONG_MAX / 2;
+}
+
#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
/*
@@ -867,6 +877,14 @@ static void rcu_print_task_stall(struct rcu_node *rnp)
{
}
+/*
+ * Because preemptible RCU does not exist, there is no need to suppress
+ * its CPU stall warnings.
+ */
+static void rcu_preempt_stall_reset(void)
+{
+}
+
#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
/*