[PATCH tip/core/rcu 01/86] rcu: Remove conditional compilation for RCU CPU stall warnings

Paul E. McKenney
2011-05-01T13:22:18Z

The RCU CPU stall warnings can now be controlled using the
rcu_cpu_stall_suppress boot-time parameter or via the same parameter
from sysfs. There is therefore no longer any reason to have
kernel config parameters for this feature. This commit therefore
removes the RCU_CPU_STALL_DETECTOR and RCU_CPU_STALL_DETECTOR_RUNNABLE
kernel config parameters. The RCU_CPU_STALL_TIMEOUT parameter remains
to allow the timeout to be tuned and the RCU_CPU_STALL_VERBOSE parameter
remains to allow task-stall information to be suppressed if desired.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
Documentation/RCU/00-INDEX | 2 +-
Documentation/RCU/stallwarn.txt | 23 +++++++++++++----------
kernel/rcutree.c | 26 +-------------------------
kernel/rcutree.h | 12 ------------
kernel/rcutree_plugin.h | 12 ------------
lib/Kconfig.debug | 30 ++----------------------------
6 files changed, 17 insertions(+), 88 deletions(-)

diff --git a/Documentation/RCU/00-INDEX b/Documentation/RCU/00-INDEX
index 71b6f50..1d7a885 100644
--- a/Documentation/RCU/00-INDEX
+++ b/Documentation/RCU/00-INDEX
@@ -21,7 +21,7 @@ rcu.txt
RTFP.txt
- List of RCU papers (bibliography) going back to 1980.
stallwarn.txt
- - RCU CPU stall warnings (CONFIG_RCU_CPU_STALL_DETECTOR)
+ - RCU CPU stall warnings (module parameter rcu_cpu_stall_suppress)
torture.txt
- RCU Torture Test Operation (CONFIG_RCU_TORTURE_TEST)
trace.txt
diff --git a/Documentation/RCU/stallwarn.txt b/Documentation/RCU/stallwarn.txt
index 862c08e..4e95920 100644
--- a/Documentation/RCU/stallwarn.txt
+++ b/Documentation/RCU/stallwarn.txt
@@ -1,22 +1,25 @@
Using RCU's CPU Stall Detector

-The CONFIG_RCU_CPU_STALL_DETECTOR kernel config parameter enables
-RCU's CPU stall detector, which detects conditions that unduly delay
-RCU grace periods. The stall detector's idea of what constitutes
-"unduly delayed" is controlled by a set of C preprocessor macros:
+The rcu_cpu_stall_suppress module parameter enables RCU's CPU stall
+detector, which detects conditions that unduly delay RCU grace periods.
+This module parameter enables CPU stall detection by default, but
+may be overridden via boot-time parameter or at runtime via sysfs.
+The stall detector's idea of what constitutes "unduly delayed" is
+controlled by a set of kernel configuration variables and cpp macros:

-RCU_SECONDS_TILL_STALL_CHECK
+CONFIG_RCU_CPU_STALL_TIMEOUT

- This macro defines the period of time that RCU will wait from
- the beginning of a grace period until it issues an RCU CPU
- stall warning. This time period is normally ten seconds.
+ This kernel configuration parameter defines the period of time
+ that RCU will wait from the beginning of a grace period until it
+ issues an RCU CPU stall warning. This time period is normally
+ ten seconds.

RCU_SECONDS_TILL_STALL_RECHECK

This macro defines the period of time that RCU will wait after
issuing a stall warning until it issues another stall warning
- for the same stall. This time period is normally set to thirty
- seconds.
+ for the same stall. This time period is normally set to three
+ times the check interval plus thirty seconds.

RCU_STALL_RAT_DELAY

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index dd4aea8..18f7a59 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -140,10 +140,8 @@ module_param(blimit, int, 0);
module_param(qhimark, int, 0);
module_param(qlowmark, int, 0);

-#ifdef CONFIG_RCU_CPU_STALL_DETECTOR
-int rcu_cpu_stall_suppress __read_mostly = RCU_CPU_STALL_SUPPRESS_INIT;
+int rcu_cpu_stall_suppress __read_mostly;
module_param(rcu_cpu_stall_suppress, int, 0644);
-#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */

static void force_quiescent_state(struct rcu_state *rsp, int relaxed);
static int rcu_pending(int cpu);
@@ -450,8 +448,6 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)

#endif /* #else #ifdef CONFIG_NO_HZ */

-#ifdef CONFIG_RCU_CPU_STALL_DETECTOR
-
int rcu_cpu_stall_suppress __read_mostly;

static void record_gp_stall_check_time(struct rcu_state *rsp)
@@ -587,26 +583,6 @@ static void __init check_cpu_stall_init(void)
atomic_notifier_chain_register(&panic_notifier_list, &rcu_panic_block);
}

-#else /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
-
-static void record_gp_stall_check_time(struct rcu_state *rsp)
-{
-}
-
-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)
-{
-}
-
-#endif /* #else #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
-
/*
* Update CPU-local rcu_data state to record the newly noticed grace period.
* This is used both when we started the grace period and when we notice
diff --git a/kernel/rcutree.h b/kernel/rcutree.h
index e8f057e..e1a6663 100644
--- a/kernel/rcutree.h
+++ b/kernel/rcutree.h
@@ -254,7 +254,6 @@ struct rcu_data {
#endif /* #else #ifdef CONFIG_NO_HZ */

#define RCU_JIFFIES_TILL_FORCE_QS 3 /* for rsp->jiffies_force_qs */
-#ifdef CONFIG_RCU_CPU_STALL_DETECTOR

#ifdef CONFIG_PROVE_RCU
#define RCU_STALL_DELAY_DELTA (5 * HZ)
@@ -272,13 +271,6 @@ struct rcu_data {
/* scheduling clock irq */
/* before ratting on them. */

-#ifdef CONFIG_RCU_CPU_STALL_DETECTOR_RUNNABLE
-#define RCU_CPU_STALL_SUPPRESS_INIT 0
-#else
-#define RCU_CPU_STALL_SUPPRESS_INIT 1
-#endif
-
-#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */

/*
* RCU global state, including node hierarchy. This hierarchy is
@@ -325,12 +317,10 @@ struct rcu_state {
/* due to lock unavailable. */
unsigned long n_force_qs_ngp; /* Number of calls leaving */
/* due to no GP active. */
-#ifdef CONFIG_RCU_CPU_STALL_DETECTOR
unsigned long gp_start; /* Time at which GP started, */
/* but in jiffies. */
unsigned long jiffies_stall; /* Time at which to check */
/* for CPU stalls. */
-#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
char *name; /* Name of structure. */
};

@@ -366,11 +356,9 @@ static int rcu_preempted_readers(struct rcu_node *rnp);
static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp,
unsigned long flags);
#endif /* #ifdef CONFIG_HOTPLUG_CPU */
-#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
static int rcu_preempt_offline_tasks(struct rcu_state *rsp,
diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index a363871..38426ef 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -54,10 +54,6 @@ static void __init rcu_bootup_announce_oddness(void)
#ifdef CONFIG_RCU_TORTURE_TEST_RUNNABLE
printk(KERN_INFO "\tRCU torture testing starts during boot.\n");
#endif
-#ifndef CONFIG_RCU_CPU_STALL_DETECTOR
- printk(KERN_INFO
- "\tRCU-based detection of stalled CPUs is disabled.\n");
-#endif
#if defined(CONFIG_TREE_PREEMPT_RCU) && !defined(CONFIG_RCU_CPU_STALL_VERBOSE)
printk(KERN_INFO "\tVerbose stalled-CPUs detection is disabled.\n");
#endif
@@ -356,8 +352,6 @@ void __rcu_read_unlock(void)
}
EXPORT_SYMBOL_GPL(__rcu_read_unlock);

-#ifdef CONFIG_RCU_CPU_STALL_DETECTOR
-
#ifdef CONFIG_RCU_CPU_STALL_VERBOSE

/*
@@ -430,8 +424,6 @@ static void rcu_preempt_stall_reset(void)
rcu_preempt_state.jiffies_stall = jiffies + ULONG_MAX / 2;
}

-#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
-
/*
* Check that the list of blocked tasks for the newly completed grace
* period is in fact empty. It is a serious bug to complete a grace
@@ -862,8 +854,6 @@ static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp, unsigned long flags)

#endif /* #ifdef CONFIG_HOTPLUG_CPU */

-#ifdef CONFIG_RCU_CPU_STALL_DETECTOR
-
/*
* Because preemptable RCU does not exist, we never have to check for
* tasks blocked within RCU read-side critical sections.
@@ -888,8 +878,6 @@ static void rcu_preempt_stall_reset(void)
{
}

-#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
-
/*
* Because there is no preemptable RCU, there can be no readers blocked,
* so there is no need to check for blocked tasks. So check only for
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index c768bcd..93ce6de 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -875,22 +875,9 @@ config RCU_TORTURE_TEST_RUNNABLE
Say N here if you want the RCU torture tests to start only
after being manually enabled via /proc.

-config RCU_CPU_STALL_DETECTOR
- bool "Check for stalled CPUs delaying RCU grace periods"
- depends on TREE_RCU || TREE_PREEMPT_RCU
- default y
- help
- This option causes RCU to printk information on which
- CPUs are delaying the current grace period, but only when
- the grace period extends for excessive time periods.
-
- Say N if you want to disable such checks.
-
- Say Y if you are unsure.
-
config RCU_CPU_STALL_TIMEOUT
int "RCU CPU stall timeout in seconds"
- depends on RCU_CPU_STALL_DETECTOR
+ depends on TREE_RCU || TREE_PREEMPT_RCU
range 3 300
default 60
help
@@ -899,22 +886,9 @@ config RCU_CPU_STALL_TIMEOUT
RCU grace period persists, additional CPU stall warnings are
printed at more widely spaced intervals.

-config RCU_CPU_STALL_DETECTOR_RUNNABLE
- bool "RCU CPU stall checking starts automatically at boot"
- depends on RCU_CPU_STALL_DETECTOR
- default y
- help
- If set, start checking for RCU CPU stalls immediately on
- boot. Otherwise, RCU CPU stall checking must be manually
- enabled.
-
- Say Y if you are unsure.
-
- Say N if you wish to suppress RCU CPU stall checking during boot.
-
config RCU_CPU_STALL_VERBOSE
bool "Print additional per-task information for RCU_CPU_STALL_DETECTOR"
- depends on RCU_CPU_STALL_DETECTOR && TREE_PREEMPT_RCU
+ depends on TREE_PREEMPT_RCU
default y
help
This option causes RCU to printk detailed per-task information
--
1.7.3.2