diff options
| -rw-r--r-- | Documentation/kernel-parameters.txt | 19 | ||||
| -rw-r--r-- | include/linux/rcupdate.h | 6 | ||||
| -rw-r--r-- | kernel/ksysfs.c | 22 | ||||
| -rw-r--r-- | kernel/rcu/srcu.c | 2 | ||||
| -rw-r--r-- | kernel/rcu/tree.c | 6 | ||||
| -rw-r--r-- | kernel/rcu/tree_plugin.h | 6 | ||||
| -rw-r--r-- | kernel/rcu/update.c | 12 |
7 files changed, 65 insertions, 8 deletions
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 742f69d18fc8..7673943d3085 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -3296,6 +3296,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted. rcutorture.verbose= [KNL] Enable additional printk() statements. + rcupdate.rcu_cpu_stall_suppress= [KNL] + Suppress RCU CPU stall warning messages. + + rcupdate.rcu_cpu_stall_timeout= [KNL] + Set timeout for RCU CPU stall warning messages. + rcupdate.rcu_expedited= [KNL] Use expedited grace-period primitives, for example, synchronize_rcu_expedited() instead @@ -3303,11 +3309,14 @@ bytes respectively. Such letter suffixes can also be entirely omitted. but can increase CPU utilization, degrade real-time latency, and degrade energy efficiency. - rcupdate.rcu_cpu_stall_suppress= [KNL] - Suppress RCU CPU stall warning messages. - - rcupdate.rcu_cpu_stall_timeout= [KNL] - Set timeout for RCU CPU stall warning messages. + rcupdate.rcu_normal= [KNL] + Use only normal grace-period primitives, + for example, synchronize_rcu() instead of + synchronize_rcu_expedited(). This improves + real-time latency, CPU utilization, and energy + efficiency, but can expose users to increased + grace-period latency. This parameter overrides + rcupdate.rcu_expedited. rcupdate.rcu_task_stall_timeout= [KNL] Set timeout in jiffies for RCU task stall warning diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index a0189ba67fde..98d9f30c02d4 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -49,9 +49,14 @@ #include <asm/barrier.h> extern int rcu_expedited; /* for sysctl */ +extern int rcu_normal; /* also for sysctl */ #ifdef CONFIG_TINY_RCU /* Tiny RCU doesn't expedite, as its purpose in life is instead to be tiny. */ +static inline bool rcu_gp_is_normal(void) /* Internal RCU use. */ +{ + return true; +} static inline bool rcu_gp_is_expedited(void) /* Internal RCU use. */ { return false; @@ -65,6 +70,7 @@ static inline void rcu_unexpedite_gp(void) { } #else /* #ifdef CONFIG_TINY_RCU */ +bool rcu_gp_is_normal(void); /* Internal RCU use. */ bool rcu_gp_is_expedited(void); /* Internal RCU use. */ void rcu_expedite_gp(void); void rcu_unexpedite_gp(void); diff --git a/kernel/ksysfs.c b/kernel/ksysfs.c index e83b26464061..b4e2fa52d8bc 100644 --- a/kernel/ksysfs.c +++ b/kernel/ksysfs.c @@ -20,7 +20,7 @@ #include <linux/capability.h> #include <linux/compiler.h> -#include <linux/rcupdate.h> /* rcu_expedited */ +#include <linux/rcupdate.h> /* rcu_expedited and rcu_normal */ #define KERNEL_ATTR_RO(_name) \ static struct kobj_attribute _name##_attr = __ATTR_RO(_name) @@ -148,7 +148,7 @@ int rcu_expedited; static ssize_t rcu_expedited_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) { - return sprintf(buf, "%d\n", rcu_expedited); + return sprintf(buf, "%d\n", READ_ONCE(rcu_expedited)); } static ssize_t rcu_expedited_store(struct kobject *kobj, struct kobj_attribute *attr, @@ -161,6 +161,23 @@ static ssize_t rcu_expedited_store(struct kobject *kobj, } KERNEL_ATTR_RW(rcu_expedited); +int rcu_normal; +static ssize_t rcu_normal_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + return sprintf(buf, "%d\n", READ_ONCE(rcu_normal)); +} +static ssize_t rcu_normal_store(struct kobject *kobj, + struct kobj_attribute *attr, + const char *buf, size_t count) +{ + if (kstrtoint(buf, 0, &rcu_normal)) + return -EINVAL; + + return count; +} +KERNEL_ATTR_RW(rcu_normal); + /* * Make /sys/kernel/notes give the raw contents of our kernel .notes section. */ @@ -203,6 +220,7 @@ static struct attribute * kernel_attrs[] = { &vmcoreinfo_attr.attr, #endif &rcu_expedited_attr.attr, + &rcu_normal_attr.attr, NULL }; diff --git a/kernel/rcu/srcu.c b/kernel/rcu/srcu.c index a63a1ea5a41b..9b9cdd549caa 100644 --- a/kernel/rcu/srcu.c +++ b/kernel/rcu/srcu.c @@ -489,7 +489,7 @@ static void __synchronize_srcu(struct srcu_struct *sp, int trycount) */ void synchronize_srcu(struct srcu_struct *sp) { - __synchronize_srcu(sp, rcu_gp_is_expedited() + __synchronize_srcu(sp, (rcu_gp_is_expedited() && !rcu_gp_is_normal()) ? SYNCHRONIZE_SRCU_EXP_TRYCOUNT : SYNCHRONIZE_SRCU_TRYCOUNT); } diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 6a652d1f3d7f..489992997c06 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -3841,6 +3841,12 @@ void synchronize_sched_expedited(void) if (rcu_blocking_is_gp()) return; + /* If expedited grace periods are prohibited, fall back to normal. */ + if (rcu_gp_is_normal()) { + wait_rcu_gp(call_rcu_sched); + return; + } + /* Take a snapshot of the sequence number. */ s = rcu_exp_gp_seq_snap(rsp); diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 57ba873d2f18..d45df3781551 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -746,6 +746,12 @@ void synchronize_rcu_expedited(void) struct rcu_state *rsp = rcu_state_p; unsigned long s; + /* If expedited grace periods are prohibited, fall back to normal. */ + if (rcu_gp_is_normal()) { + wait_rcu_gp(call_rcu); + return; + } + s = rcu_exp_gp_seq_snap(rsp); rnp_unlock = exp_funnel_lock(rsp, s); diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c index 5f748c5a40f0..8fccda3a794d 100644 --- a/kernel/rcu/update.c +++ b/kernel/rcu/update.c @@ -61,6 +61,7 @@ MODULE_ALIAS("rcupdate"); #define MODULE_PARAM_PREFIX "rcupdate." module_param(rcu_expedited, int, 0); +module_param(rcu_normal, int, 0); #if defined(CONFIG_DEBUG_LOCK_ALLOC) && defined(CONFIG_PREEMPT_COUNT) /** @@ -113,6 +114,17 @@ EXPORT_SYMBOL(rcu_read_lock_sched_held); #ifndef CONFIG_TINY_RCU +/* + * Should expedited grace-period primitives always fall back to their + * non-expedited counterparts? Intended for use within RCU. Note + * that if the user specifies both rcu_expedited and rcu_normal, then + * rcu_normal wins. + */ +bool rcu_gp_is_normal(void) +{ + return READ_ONCE(rcu_normal); +} + static atomic_t rcu_expedited_nesting = ATOMIC_INIT(IS_ENABLED(CONFIG_RCU_EXPEDITE_BOOT) ? 1 : 0); |