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Merge branches 'doctorture.2013.01.29a', 'fixes.2013.01.26a', 'tagcb.2013.01.24a' and 'tiny.2013.01.29b' into HEAD 

doctorture.2013.01.11a: Changes to rcutorture and to RCU documentation.

fixes.2013.01.26a: Miscellaneous fixes.

tagcb.2013.01.24a: Tag RCU callbacks with grace-period number to
	simplify callback advancement.

tiny.2013.01.29b: Enhancements to uniprocessor handling in tiny RCU.
This commit is contained in:
Paul E. McKenney 2013-01-28 22:25:02 -08:00
parent 0e11c8e8a6 4eacdf1837 6d4b418c75 9fc52d832b
commit 40393f525f
12 changed files with 449 additions and 163 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/linux/rcupdate.h
View File

@ -756,7 +756,7 @@ static inline void rcu_preempt_sleep_check(void)
* preemptible RCU implementations (TREE_PREEMPT_RCU and TINY_PREEMPT_RCU)
* in CONFIG_PREEMPT kernel builds, RCU read-side critical sections may
* be preempted, but explicit blocking is illegal. Finally, in preemptible
* RCU implementations in real-time (CONFIG_PREEMPT_RT) kernel builds,
* RCU implementations in real-time (with -rt patchset) kernel builds,
* RCU read-side critical sections may be preempted and they may also
* block, but only when acquiring spinlocks that are subject to priority
* inheritance.

12
include/trace/events/rcu.h
View File

@ -44,8 +44,10 @@ TRACE_EVENT(rcu_utilization,
* of a new grace period or the end of an old grace period ("cpustart"
* and "cpuend", respectively), a CPU passing through a quiescent
* state ("cpuqs"), a CPU coming online or going offline ("cpuonl"
* and "cpuofl", respectively), and a CPU being kicked for being too
* long in dyntick-idle mode ("kick").
* and "cpuofl", respectively), a CPU being kicked for being too
* long in dyntick-idle mode ("kick"), a CPU accelerating its new
* callbacks to RCU_NEXT_READY_TAIL ("AccReadyCB"), and a CPU
* accelerating its new callbacks to RCU_WAIT_TAIL ("AccWaitCB").
*/
TRACE_EVENT(rcu_grace_period,
@ -393,7 +395,7 @@ TRACE_EVENT(rcu_kfree_callback,
*/
TRACE_EVENT(rcu_batch_start,
TP_PROTO(char *rcuname, long qlen_lazy, long qlen, int blimit),
TP_PROTO(char *rcuname, long qlen_lazy, long qlen, long blimit),
TP_ARGS(rcuname, qlen_lazy, qlen, blimit),
@ -401,7 +403,7 @@ TRACE_EVENT(rcu_batch_start,
__field(char *, rcuname)
__field(long, qlen_lazy)
__field(long, qlen)
__field(int, blimit)
__field(long, blimit)
),
TP_fast_assign(
@ -411,7 +413,7 @@ TRACE_EVENT(rcu_batch_start,
__entry->blimit = blimit;
),
TP_printk("%s CBs=%ld/%ld bl=%d",
TP_printk("%s CBs=%ld/%ld bl=%ld",
__entry->rcuname, __entry->qlen_lazy, __entry->qlen,
__entry->blimit)
);

12
init/Kconfig
View File

@ -453,7 +453,7 @@ config TREE_RCU
config TREE_PREEMPT_RCU
bool "Preemptible tree-based hierarchical RCU"
depends on PREEMPT && SMP
depends on PREEMPT
help
This option selects the RCU implementation that is
designed for very large SMP systems with hundreds or
@ -461,6 +461,8 @@ config TREE_PREEMPT_RCU
is also required. It also scales down nicely to
smaller systems.
Select this option if you are unsure.
config TINY_RCU
bool "UP-only small-memory-footprint RCU"
depends on !PREEMPT && !SMP
@ -486,6 +488,14 @@ config PREEMPT_RCU
This option enables preemptible-RCU code that is common between
the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
config RCU_STALL_COMMON
def_bool ( TREE_RCU || TREE_PREEMPT_RCU || RCU_TRACE )
help
This option enables RCU CPU stall code that is common between
the TINY and TREE variants of RCU. The purpose is to allow
the tiny variants to disable RCU CPU stall warnings, while
making these warnings mandatory for the tree variants.
config CONTEXT_TRACKING
bool

75
kernel/context_tracking.c
View File

@ -1,3 +1,19 @@
/*
* Context tracking: Probe on high level context boundaries such as kernel
* and userspace. This includes syscalls and exceptions entry/exit.
*
* This is used by RCU to remove its dependency on the timer tick while a CPU
* runs in userspace.
*
* Started by Frederic Weisbecker:
*
* Copyright (C) 2012 Red Hat, Inc., Frederic Weisbecker <fweisbec@redhat.com>
*
* Many thanks to Gilad Ben-Yossef, Paul McKenney, Ingo Molnar, Andrew Morton,
* Steven Rostedt, Peter Zijlstra for suggestions and improvements.
*
*/
#include <linux/context_tracking.h>
#include <linux/rcupdate.h>
#include <linux/sched.h>
@ -6,8 +22,8 @@
struct context_tracking {
/*
* When active is false, hooks are not set to
* minimize overhead: TIF flags are cleared
* When active is false, probes are unset in order
* to minimize overhead: TIF flags are cleared
* and calls to user_enter/exit are ignored. This
* may be further optimized using static keys.
*/
@ -24,6 +40,15 @@ static DEFINE_PER_CPU(struct context_tracking, context_tracking) = {
#endif
};
/**
* user_enter - Inform the context tracking that the CPU is going to
* enter userspace mode.
*
* This function must be called right before we switch from the kernel
* to userspace, when it's guaranteed the remaining kernel instructions
* to execute won't use any RCU read side critical section because this
* function sets RCU in extended quiescent state.
*/
void user_enter(void)
{
unsigned long flags;
@ -39,40 +64,70 @@ void user_enter(void)
if (in_interrupt())
return;
/* Kernel threads aren't supposed to go to userspace */
WARN_ON_ONCE(!current->mm);
local_irq_save(flags);
if (__this_cpu_read(context_tracking.active) &&
__this_cpu_read(context_tracking.state) != IN_USER) {
__this_cpu_write(context_tracking.state, IN_USER);
/*
* At this stage, only low level arch entry code remains and
* then we'll run in userspace. We can assume there won't be
* any RCU read-side critical section until the next call to
* user_exit() or rcu_irq_enter(). Let's remove RCU's dependency
* on the tick.
*/
rcu_user_enter();
}
local_irq_restore(flags);
}
/**
* user_exit - Inform the context tracking that the CPU is
* exiting userspace mode and entering the kernel.
*
* This function must be called after we entered the kernel from userspace
* before any use of RCU read side critical section. This potentially include
* any high level kernel code like syscalls, exceptions, signal handling, etc...
*
* This call supports re-entrancy. This way it can be called from any exception
* handler without needing to know if we came from userspace or not.
*/
void user_exit(void)
{
unsigned long flags;
/*
* Some contexts may involve an exception occuring in an irq,
* leading to that nesting:
* rcu_irq_enter() rcu_user_exit() rcu_user_exit() rcu_irq_exit()
* This would mess up the dyntick_nesting count though. And rcu_irq_*()
* helpers are enough to protect RCU uses inside the exception. So
* just return immediately if we detect we are in an IRQ.
*/
if (in_interrupt())
return;
local_irq_save(flags);
if (__this_cpu_read(context_tracking.state) == IN_USER) {
__this_cpu_write(context_tracking.state, IN_KERNEL);
/*
* We are going to run code that may use RCU. Inform
* RCU core about that (ie: we may need the tick again).
*/
rcu_user_exit();
}
local_irq_restore(flags);
}
/**
* context_tracking_task_switch - context switch the syscall callbacks
* @prev: the task that is being switched out
* @next: the task that is being switched in
*
* The context tracking uses the syscall slow path to implement its user-kernel
* boundaries probes on syscalls. This way it doesn't impact the syscall fast
* path on CPUs that don't do context tracking.
*
* But we need to clear the flag on the previous task because it may later
* migrate to some CPU that doesn't do the context tracking. As such the TIF
* flag may not be desired there.
*/
void context_tracking_task_switch(struct task_struct *prev,
struct task_struct *next)
{

7
kernel/rcu.h
View File

@ -111,4 +111,11 @@ static inline bool __rcu_reclaim(char *rn, struct rcu_head *head)
extern int rcu_expedited;
#ifdef CONFIG_RCU_STALL_COMMON
extern int rcu_cpu_stall_suppress;
int rcu_jiffies_till_stall_check(void);
#endif /* #ifdef CONFIG_RCU_STALL_COMMON */
#endif /* __LINUX_RCU_H */

51
kernel/rcupdate.c
View File

@ -415,3 +415,54 @@ EXPORT_SYMBOL_GPL(do_trace_rcu_torture_read);
#define do_trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \
do { } while (0)
#endif
#ifdef CONFIG_RCU_STALL_COMMON
#ifdef CONFIG_PROVE_RCU
#define RCU_STALL_DELAY_DELTA (5 * HZ)
#else
#define RCU_STALL_DELAY_DELTA 0
#endif
int rcu_cpu_stall_suppress __read_mostly; /* 1 = suppress stall warnings. */
int rcu_cpu_stall_timeout __read_mostly = CONFIG_RCU_CPU_STALL_TIMEOUT;
module_param(rcu_cpu_stall_suppress, int, 0644);
module_param(rcu_cpu_stall_timeout, int, 0644);
int rcu_jiffies_till_stall_check(void)
{
int till_stall_check = ACCESS_ONCE(rcu_cpu_stall_timeout);
/*
* Limit check must be consistent with the Kconfig limits
* for CONFIG_RCU_CPU_STALL_TIMEOUT.
*/
if (till_stall_check < 3) {
ACCESS_ONCE(rcu_cpu_stall_timeout) = 3;
till_stall_check = 3;
} else if (till_stall_check > 300) {
ACCESS_ONCE(rcu_cpu_stall_timeout) = 300;
till_stall_check = 300;
}
return till_stall_check * HZ + RCU_STALL_DELAY_DELTA;
}
static int rcu_panic(struct notifier_block *this, unsigned long ev, void *ptr)
{
rcu_cpu_stall_suppress = 1;
return NOTIFY_DONE;
}
static struct notifier_block rcu_panic_block = {
.notifier_call = rcu_panic,
};
static int __init check_cpu_stall_init(void)
{
atomic_notifier_chain_register(&panic_notifier_list, &rcu_panic_block);
return 0;
}
early_initcall(check_cpu_stall_init);
#endif /* #ifdef CONFIG_RCU_STALL_COMMON */

8
kernel/rcutiny.c
View File

@ -51,10 +51,10 @@ static void __call_rcu(struct rcu_head *head,
void (*func)(struct rcu_head *rcu),
struct rcu_ctrlblk *rcp);
#include "rcutiny_plugin.h"
static long long rcu_dynticks_nesting = DYNTICK_TASK_EXIT_IDLE;
#include "rcutiny_plugin.h"
/* Common code for rcu_idle_enter() and rcu_irq_exit(), see kernel/rcutree.c. */
static void rcu_idle_enter_common(long long newval)
{
@ -193,7 +193,7 @@ EXPORT_SYMBOL(rcu_is_cpu_idle);
* interrupts don't count, we must be running at the first interrupt
* level.
*/
int rcu_is_cpu_rrupt_from_idle(void)
static int rcu_is_cpu_rrupt_from_idle(void)
{
return rcu_dynticks_nesting <= 1;
}
@ -205,6 +205,7 @@ int rcu_is_cpu_rrupt_from_idle(void)
*/
static int rcu_qsctr_help(struct rcu_ctrlblk *rcp)
{
reset_cpu_stall_ticks(rcp);
if (rcp->rcucblist != NULL &&
rcp->donetail != rcp->curtail) {
rcp->donetail = rcp->curtail;
@ -251,6 +252,7 @@ void rcu_bh_qs(int cpu)
*/
void rcu_check_callbacks(int cpu, int user)
{
check_cpu_stalls();
if (user || rcu_is_cpu_rrupt_from_idle())
rcu_sched_qs(cpu);
else if (!in_softirq())

56
kernel/rcutiny_plugin.h
View File

@ -33,6 +33,9 @@ struct rcu_ctrlblk {
struct rcu_head **donetail; /* ->next pointer of last "done" CB. */
struct rcu_head **curtail; /* ->next pointer of last CB. */
RCU_TRACE(long qlen); /* Number of pending CBs. */
RCU_TRACE(unsigned long gp_start); /* Start time for stalls. */
RCU_TRACE(unsigned long ticks_this_gp); /* Statistic for stalls. */
RCU_TRACE(unsigned long jiffies_stall); /* Jiffies at next stall. */
RCU_TRACE(char *name); /* Name of RCU type. */
};
@ -54,6 +57,51 @@ int rcu_scheduler_active __read_mostly;
EXPORT_SYMBOL_GPL(rcu_scheduler_active);
#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
#ifdef CONFIG_RCU_TRACE
static void check_cpu_stall(struct rcu_ctrlblk *rcp)
{
unsigned long j;
unsigned long js;
if (rcu_cpu_stall_suppress)
return;
rcp->ticks_this_gp++;
j = jiffies;
js = rcp->jiffies_stall;
if (*rcp->curtail && ULONG_CMP_GE(j, js)) {
pr_err("INFO: %s stall on CPU (%lu ticks this GP) idle=%llx (t=%lu jiffies q=%ld)\n",
rcp->name, rcp->ticks_this_gp, rcu_dynticks_nesting,
jiffies - rcp->gp_start, rcp->qlen);
dump_stack();
}
if (*rcp->curtail && ULONG_CMP_GE(j, js))
rcp->jiffies_stall = jiffies +
3 * rcu_jiffies_till_stall_check() + 3;
else if (ULONG_CMP_GE(j, js))
rcp->jiffies_stall = jiffies + rcu_jiffies_till_stall_check();
}
static void check_cpu_stall_preempt(void);
#endif /* #ifdef CONFIG_RCU_TRACE */
static void reset_cpu_stall_ticks(struct rcu_ctrlblk *rcp)
{
#ifdef CONFIG_RCU_TRACE
rcp->ticks_this_gp = 0;
rcp->gp_start = jiffies;
rcp->jiffies_stall = jiffies + rcu_jiffies_till_stall_check();
#endif /* #ifdef CONFIG_RCU_TRACE */
}
static void check_cpu_stalls(void)
{
RCU_TRACE(check_cpu_stall(&rcu_bh_ctrlblk));
RCU_TRACE(check_cpu_stall(&rcu_sched_ctrlblk));
RCU_TRACE(check_cpu_stall_preempt());
}
#ifdef CONFIG_TINY_PREEMPT_RCU
#include <linux/delay.h>
@ -448,6 +496,7 @@ static void rcu_preempt_start_gp(void)
/* Official start of GP. */
rcu_preempt_ctrlblk.gpnum++;
RCU_TRACE(rcu_preempt_ctrlblk.n_grace_periods++);
reset_cpu_stall_ticks(&rcu_preempt_ctrlblk.rcb);
/* Any blocked RCU readers block new GP. */
if (rcu_preempt_blocked_readers_any())
@ -1054,4 +1103,11 @@ MODULE_AUTHOR("Paul E. McKenney");
MODULE_DESCRIPTION("Read-Copy Update tracing for tiny implementation");
MODULE_LICENSE("GPL");
static void check_cpu_stall_preempt(void)
{
#ifdef CONFIG_TINY_PREEMPT_RCU
check_cpu_stall(&rcu_preempt_ctrlblk.rcb);
#endif /* #ifdef CONFIG_TINY_PREEMPT_RCU */
}
#endif /* #ifdef CONFIG_RCU_TRACE */

2
kernel/rcutorture.c
View File

@ -1782,7 +1782,7 @@ static int rcu_torture_barrier_init(void)
barrier_cbs_wq =
kzalloc(n_barrier_cbs * sizeof(barrier_cbs_wq[0]),
GFP_KERNEL);
if (barrier_cbs_tasks == NULL || barrier_cbs_wq == 0)
if (barrier_cbs_tasks == NULL || !barrier_cbs_wq)
return -ENOMEM;
for (i = 0; i < n_barrier_cbs; i++) {
init_waitqueue_head(&barrier_cbs_wq[i]);

260
kernel/rcutree.c
View File

@ -105,7 +105,7 @@ int rcu_num_nodes __read_mostly = NUM_RCU_NODES; /* Total # rcu_nodes in use. */
* The rcu_scheduler_active variable transitions from zero to one just
* before the first task is spawned. So when this variable is zero, RCU
* can assume that there is but one task, allowing RCU to (for example)
* optimized synchronize_sched() to a simple barrier(). When this variable
* optimize synchronize_sched() to a simple barrier(). When this variable
* is one, RCU must actually do all the hard work required to detect real
* grace periods. This variable is also used to suppress boot-time false
* positives from lockdep-RCU error checking.
@ -217,12 +217,6 @@ module_param(blimit, long, 0444);
module_param(qhimark, long, 0444);
module_param(qlowmark, long, 0444);
int rcu_cpu_stall_suppress __read_mostly; /* 1 = suppress stall warnings. */
int rcu_cpu_stall_timeout __read_mostly = CONFIG_RCU_CPU_STALL_TIMEOUT;
module_param(rcu_cpu_stall_suppress, int, 0644);
module_param(rcu_cpu_stall_timeout, int, 0644);
static ulong jiffies_till_first_fqs = RCU_JIFFIES_TILL_FORCE_QS;
static ulong jiffies_till_next_fqs = RCU_JIFFIES_TILL_FORCE_QS;
@ -305,17 +299,27 @@ cpu_has_callbacks_ready_to_invoke(struct rcu_data *rdp)
}
/*
* Does the current CPU require a yet-as-unscheduled grace period?
* Does the current CPU require a not-yet-started grace period?
* The caller must have disabled interrupts to prevent races with
* normal callback registry.
*/
static int
cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp)
{
struct rcu_head **ntp;
int i;
ntp = rdp->nxttail[RCU_DONE_TAIL +
(ACCESS_ONCE(rsp->completed) != rdp->completed)];
return rdp->nxttail[RCU_DONE_TAIL] && ntp && *ntp &&
!rcu_gp_in_progress(rsp);
if (rcu_gp_in_progress(rsp))
return 0; /* No, a grace period is already in progress. */
if (!rdp->nxttail[RCU_NEXT_TAIL])
return 0; /* No, this is a no-CBs (or offline) CPU. */
if (*rdp->nxttail[RCU_NEXT_READY_TAIL])
return 1; /* Yes, this CPU has newly registered callbacks. */
for (i = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++)
if (rdp->nxttail[i - 1] != rdp->nxttail[i] &&
ULONG_CMP_LT(ACCESS_ONCE(rsp->completed),
rdp->nxtcompleted[i]))
return 1; /* Yes, CBs for future grace period. */
return 0; /* No grace period needed. */
}
/*
@ -336,7 +340,7 @@ static struct rcu_node *rcu_get_root(struct rcu_state *rsp)
static void rcu_eqs_enter_common(struct rcu_dynticks *rdtp, long long oldval,
bool user)
{
trace_rcu_dyntick("Start", oldval, 0);
trace_rcu_dyntick("Start", oldval, rdtp->dynticks_nesting);
if (!user && !is_idle_task(current)) {
struct task_struct *idle = idle_task(smp_processor_id());
@ -727,7 +731,7 @@ EXPORT_SYMBOL_GPL(rcu_lockdep_current_cpu_online);
* interrupt from idle, return true. The caller must have at least
* disabled preemption.
*/
int rcu_is_cpu_rrupt_from_idle(void)
static int rcu_is_cpu_rrupt_from_idle(void)
{
return __get_cpu_var(rcu_dynticks).dynticks_nesting <= 1;
}
@ -793,28 +797,10 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
return 0;
}
static int jiffies_till_stall_check(void)
{
int till_stall_check = ACCESS_ONCE(rcu_cpu_stall_timeout);
/*
* Limit check must be consistent with the Kconfig limits
* for CONFIG_RCU_CPU_STALL_TIMEOUT.
*/
if (till_stall_check < 3) {
ACCESS_ONCE(rcu_cpu_stall_timeout) = 3;
till_stall_check = 3;
} else if (till_stall_check > 300) {
ACCESS_ONCE(rcu_cpu_stall_timeout) = 300;
till_stall_check = 300;
}
return till_stall_check * HZ + RCU_STALL_DELAY_DELTA;
}
static void record_gp_stall_check_time(struct rcu_state *rsp)
{
rsp->gp_start = jiffies;
rsp->jiffies_stall = jiffies + jiffies_till_stall_check();
rsp->jiffies_stall = jiffies + rcu_jiffies_till_stall_check();
}
/*
@ -857,7 +843,7 @@ static void print_other_cpu_stall(struct rcu_state *rsp)
raw_spin_unlock_irqrestore(&rnp->lock, flags);
return;
}
rsp->jiffies_stall = jiffies + 3 * jiffies_till_stall_check() + 3;
rsp->jiffies_stall = jiffies + 3 * rcu_jiffies_till_stall_check() + 3;
raw_spin_unlock_irqrestore(&rnp->lock, flags);
/*
@ -935,7 +921,7 @@ static void print_cpu_stall(struct rcu_state *rsp)
raw_spin_lock_irqsave(&rnp->lock, flags);
if (ULONG_CMP_GE(jiffies, rsp->jiffies_stall))
rsp->jiffies_stall = jiffies +
3 * jiffies_till_stall_check() + 3;
3 * rcu_jiffies_till_stall_check() + 3;
raw_spin_unlock_irqrestore(&rnp->lock, flags);
set_need_resched(); /* kick ourselves to get things going. */
@ -966,12 +952,6 @@ static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp)
}
}
static int rcu_panic(struct notifier_block *this, unsigned long ev, void *ptr)
{
rcu_cpu_stall_suppress = 1;
return NOTIFY_DONE;
}
/**
* rcu_cpu_stall_reset - prevent further stall warnings in current grace period
*
@ -989,15 +969,6 @@ void rcu_cpu_stall_reset(void)
rsp->jiffies_stall = jiffies + ULONG_MAX / 2;
}
static struct notifier_block rcu_panic_block = {
.notifier_call = rcu_panic,
};
static void __init check_cpu_stall_init(void)
{
atomic_notifier_chain_register(&panic_notifier_list, &rcu_panic_block);
}
/*
* 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
@ -1070,6 +1041,145 @@ static void init_callback_list(struct rcu_data *rdp)
init_nocb_callback_list(rdp);
}
/*
* Determine the value that ->completed will have at the end of the
* next subsequent grace period. This is used to tag callbacks so that
* a CPU can invoke callbacks in a timely fashion even if that CPU has
* been dyntick-idle for an extended period with callbacks under the
* influence of RCU_FAST_NO_HZ.
*
* The caller must hold rnp->lock with interrupts disabled.
*/
static unsigned long rcu_cbs_completed(struct rcu_state *rsp,
struct rcu_node *rnp)
{
/*
* If RCU is idle, we just wait for the next grace period.
* But we can only be sure that RCU is idle if we are looking
* at the root rcu_node structure -- otherwise, a new grace
* period might have started, but just not yet gotten around
* to initializing the current non-root rcu_node structure.
*/
if (rcu_get_root(rsp) == rnp && rnp->gpnum == rnp->completed)
return rnp->completed + 1;
/*
* Otherwise, wait for a possible partial grace period and
* then the subsequent full grace period.
*/
return rnp->completed + 2;
}
/*
* If there is room, assign a ->completed number to any callbacks on
* this CPU that have not already been assigned. Also accelerate any
* callbacks that were previously assigned a ->completed number that has
* since proven to be too conservative, which can happen if callbacks get
* assigned a ->completed number while RCU is idle, but with reference to
* a non-root rcu_node structure. This function is idempotent, so it does
* not hurt to call it repeatedly.
*
* The caller must hold rnp->lock with interrupts disabled.
*/
static void rcu_accelerate_cbs(struct rcu_state *rsp, struct rcu_node *rnp,
struct rcu_data *rdp)
{
unsigned long c;
int i;
/* If the CPU has no callbacks, nothing to do. */
if (!rdp->nxttail[RCU_NEXT_TAIL] || !*rdp->nxttail[RCU_DONE_TAIL])
return;
/*
* Starting from the sublist containing the callbacks most
* recently assigned a ->completed number and working down, find the
* first sublist that is not assignable to an upcoming grace period.
* Such a sublist has something in it (first two tests) and has
* a ->completed number assigned that will complete sooner than
* the ->completed number for newly arrived callbacks (last test).
*
* The key point is that any later sublist can be assigned the
* same ->completed number as the newly arrived callbacks, which
* means that the callbacks in any of these later sublist can be
* grouped into a single sublist, whether or not they have already
* been assigned a ->completed number.
*/
c = rcu_cbs_completed(rsp, rnp);
for (i = RCU_NEXT_TAIL - 1; i > RCU_DONE_TAIL; i--)
if (rdp->nxttail[i] != rdp->nxttail[i - 1] &&
!ULONG_CMP_GE(rdp->nxtcompleted[i], c))
break;
/*
* If there are no sublist for unassigned callbacks, leave.
* At the same time, advance "i" one sublist, so that "i" will
* index into the sublist where all the remaining callbacks should
* be grouped into.
*/
if (++i >= RCU_NEXT_TAIL)
return;
/*
* Assign all subsequent callbacks' ->completed number to the next
* full grace period and group them all in the sublist initially
* indexed by "i".
*/
for (; i <= RCU_NEXT_TAIL; i++) {
rdp->nxttail[i] = rdp->nxttail[RCU_NEXT_TAIL];
rdp->nxtcompleted[i] = c;
}
/* Trace depending on how much we were able to accelerate. */
if (!*rdp->nxttail[RCU_WAIT_TAIL])
trace_rcu_grace_period(rsp->name, rdp->gpnum, "AccWaitCB");
else
trace_rcu_grace_period(rsp->name, rdp->gpnum, "AccReadyCB");
}
/*
* Move any callbacks whose grace period has completed to the
* RCU_DONE_TAIL sublist, then compact the remaining sublists and
* assign ->completed numbers to any callbacks in the RCU_NEXT_TAIL
* sublist. This function is idempotent, so it does not hurt to
* invoke it repeatedly. As long as it is not invoked -too- often...
*
* The caller must hold rnp->lock with interrupts disabled.
*/
static void rcu_advance_cbs(struct rcu_state *rsp, struct rcu_node *rnp,
struct rcu_data *rdp)
{
int i, j;
/* If the CPU has no callbacks, nothing to do. */
if (!rdp->nxttail[RCU_NEXT_TAIL] || !*rdp->nxttail[RCU_DONE_TAIL])
return;
/*
* Find all callbacks whose ->completed numbers indicate that they
* are ready to invoke, and put them into the RCU_DONE_TAIL sublist.
*/
for (i = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++) {
if (ULONG_CMP_LT(rnp->completed, rdp->nxtcompleted[i]))
break;
rdp->nxttail[RCU_DONE_TAIL] = rdp->nxttail[i];
}
/* Clean up any sublist tail pointers that were misordered above. */
for (j = RCU_WAIT_TAIL; j < i; j++)
rdp->nxttail[j] = rdp->nxttail[RCU_DONE_TAIL];
/* Copy down callbacks to fill in empty sublists. */
for (j = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++, j++) {
if (rdp->nxttail[j] == rdp->nxttail[RCU_NEXT_TAIL])
break;
rdp->nxttail[j] = rdp->nxttail[i];
rdp->nxtcompleted[j] = rdp->nxtcompleted[i];
}
/* Classify any remaining callbacks. */
rcu_accelerate_cbs(rsp, rnp, rdp);
}
/*
* Advance this CPU's callbacks, but only if the current grace period
* has ended. This may be called only from the CPU to whom the rdp
@ -1080,12 +1190,15 @@ static void
__rcu_process_gp_end(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp)
{
/* Did another grace period end? */
if (rdp->completed != rnp->completed) {
if (rdp->completed == rnp->completed) {
/* Advance callbacks. No harm if list empty. */
rdp->nxttail[RCU_DONE_TAIL] = rdp->nxttail[RCU_WAIT_TAIL];
rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_READY_TAIL];
rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
/* No, so just accelerate recent callbacks. */
rcu_accelerate_cbs(rsp, rnp, rdp);
} else {
/* Advance callbacks. */
rcu_advance_cbs(rsp, rnp, rdp);
/* Remember that we saw this grace-period completion. */
rdp->completed = rnp->completed;
@ -1392,17 +1505,10 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
/*
* Because there is no grace period in progress right now,
* any callbacks we have up to this point will be satisfied
* by the next grace period. So promote all callbacks to be
* handled after the end of the next grace period. If the
* CPU is not yet aware of the end of the previous grace period,
* we need to allow for the callback advancement that will
* occur when it does become aware. Deadlock prevents us from
* making it aware at this point: We cannot acquire a leaf
* rcu_node ->lock while holding the root rcu_node ->lock.
* by the next grace period. So this is a good place to
* assign a grace period number to recently posted callbacks.
*/
rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
if (rdp->completed == rsp->completed)
rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
rcu_accelerate_cbs(rsp, rnp, rdp);
rsp->gp_flags = RCU_GP_FLAG_INIT;
raw_spin_unlock(&rnp->lock); /* Interrupts remain disabled. */
@ -1527,7 +1633,7 @@ rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp)
* This GP can't end until cpu checks in, so all of our
* callbacks can be processed during the next GP.
*/
rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
rcu_accelerate_cbs(rsp, rnp, rdp);
rcu_report_qs_rnp(mask, rsp, rnp, flags); /* rlses rnp->lock */
}
@ -1779,7 +1885,7 @@ static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp)
long bl, count, count_lazy;
int i;
/* If no callbacks are ready, just return.*/
/* If no callbacks are ready, just return. */
if (!cpu_has_callbacks_ready_to_invoke(rdp)) {
trace_rcu_batch_start(rsp->name, rdp->qlen_lazy, rdp->qlen, 0);
trace_rcu_batch_end(rsp->name, 0, !!ACCESS_ONCE(rdp->nxtlist),
@ -2008,19 +2114,19 @@ __rcu_process_callbacks(struct rcu_state *rsp)
WARN_ON_ONCE(rdp->beenonline == 0);
/*
* Advance callbacks in response to end of earlier grace
* period that some other CPU ended.
*/
/* Handle the end of a grace period that some other CPU ended. */
rcu_process_gp_end(rsp, rdp);
/* Update RCU state based on any recent quiescent states. */
rcu_check_quiescent_state(rsp, rdp);
/* Does this CPU require a not-yet-started grace period? */
local_irq_save(flags);
if (cpu_needs_another_gp(rsp, rdp)) {
raw_spin_lock_irqsave(&rcu_get_root(rsp)->lock, flags);
raw_spin_lock(&rcu_get_root(rsp)->lock); /* irqs disabled. */
rcu_start_gp(rsp, flags); /* releases above lock */
} else {
local_irq_restore(flags);
}
/* If there are callbacks ready, invoke them. */
@ -2719,9 +2825,6 @@ rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp)
rdp->dynticks = &per_cpu(rcu_dynticks, cpu);
WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != DYNTICK_TASK_EXIT_IDLE);
WARN_ON_ONCE(atomic_read(&rdp->dynticks->dynticks) != 1);
#ifdef CONFIG_RCU_USER_QS
WARN_ON_ONCE(rdp->dynticks->in_user);
#endif
rdp->cpu = cpu;
rdp->rsp = rsp;
rcu_boot_init_nocb_percpu_data(rdp);
@ -2938,6 +3041,10 @@ static void __init rcu_init_one(struct rcu_state *rsp,
BUILD_BUG_ON(MAX_RCU_LVLS > ARRAY_SIZE(buf)); /* Fix buf[] init! */
/* Silence gcc 4.8 warning about array index out of range. */
if (rcu_num_lvls > RCU_NUM_LVLS)
panic("rcu_init_one: rcu_num_lvls overflow");
/* Initialize the level-tracking arrays. */
for (i = 0; i < rcu_num_lvls; i++)
@ -3074,7 +3181,6 @@ void __init rcu_init(void)
cpu_notifier(rcu_cpu_notify, 0);
for_each_online_cpu(cpu)
rcu_cpu_notify(NULL, CPU_UP_PREPARE, (void *)(long)cpu);
check_cpu_stall_init();
}
#include "rcutree_plugin.h"

11
kernel/rcutree.h
View File

@ -102,10 +102,6 @@ struct rcu_dynticks {
/* idle-period nonlazy_posted snapshot. */
int tick_nohz_enabled_snap; /* Previously seen value from sysfs. */
#endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */
#ifdef CONFIG_RCU_USER_QS
bool ignore_user_qs; /* Treat userspace as extended QS or not */
bool in_user; /* Is the CPU in userland from RCU POV? */
#endif
};
/* RCU's kthread states for tracing. */
@ -282,6 +278,8 @@ struct rcu_data {
*/
struct rcu_head *nxtlist;
struct rcu_head **nxttail[RCU_NEXT_SIZE];
unsigned long nxtcompleted[RCU_NEXT_SIZE];
/* grace periods for sublists. */
long qlen_lazy; /* # of lazy queued callbacks */
long qlen; /* # of queued callbacks, incl lazy */
long qlen_last_fqs_check;
@ -343,11 +341,6 @@ struct rcu_data {
#define RCU_JIFFIES_TILL_FORCE_QS 3 /* for rsp->jiffies_force_qs */
#ifdef CONFIG_PROVE_RCU
#define RCU_STALL_DELAY_DELTA (5 * HZ)
#else
#define RCU_STALL_DELAY_DELTA 0
#endif
#define RCU_STALL_RAT_DELAY 2 /* Allow other CPUs time */
/* to take at least one */
/* scheduling clock irq */

116
lib/Kconfig.debug
View File

@ -605,61 +605,6 @@ config PROVE_LOCKING
For more details, see Documentation/lockdep-design.txt.
config PROVE_RCU
bool "RCU debugging: prove RCU correctness"
depends on PROVE_LOCKING
default n
help
This feature enables lockdep extensions that check for correct
use of RCU APIs. This is currently under development. Say Y
if you want to debug RCU usage or help work on the PROVE_RCU
feature.
Say N if you are unsure.
config PROVE_RCU_REPEATEDLY
bool "RCU debugging: don't disable PROVE_RCU on first splat"
depends on PROVE_RCU
default n
help
By itself, PROVE_RCU will disable checking upon issuing the
first warning (or "splat"). This feature prevents such
disabling, allowing multiple RCU-lockdep warnings to be printed
on a single reboot.
Say Y to allow multiple RCU-lockdep warnings per boot.
Say N if you are unsure.
config PROVE_RCU_DELAY
bool "RCU debugging: preemptible RCU race provocation"
depends on DEBUG_KERNEL && PREEMPT_RCU
default n
help
There is a class of races that involve an unlikely preemption
of __rcu_read_unlock() just after ->rcu_read_lock_nesting has
been set to INT_MIN. This feature inserts a delay at that
point to increase the probability of these races.
Say Y to increase probability of preemption of __rcu_read_unlock().
Say N if you are unsure.
config SPARSE_RCU_POINTER
bool "RCU debugging: sparse-based checks for pointer usage"
default n
help
This feature enables the __rcu sparse annotation for
RCU-protected pointers. This annotation will cause sparse
to flag any non-RCU used of annotated pointers. This can be
helpful when debugging RCU usage. Please note that this feature
is not intended to enforce code cleanliness; it is instead merely
a debugging aid.
Say Y to make sparse flag questionable use of RCU-protected pointers
Say N if you are unsure.
config LOCKDEP
bool
depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
@ -937,6 +882,63 @@ config BOOT_PRINTK_DELAY
BOOT_PRINTK_DELAY also may cause LOCKUP_DETECTOR to detect
what it believes to be lockup conditions.
menu "RCU Debugging"
config PROVE_RCU
bool "RCU debugging: prove RCU correctness"
depends on PROVE_LOCKING
default n
help
This feature enables lockdep extensions that check for correct
use of RCU APIs. This is currently under development. Say Y
if you want to debug RCU usage or help work on the PROVE_RCU
feature.
Say N if you are unsure.
config PROVE_RCU_REPEATEDLY
bool "RCU debugging: don't disable PROVE_RCU on first splat"
depends on PROVE_RCU
default n
help
By itself, PROVE_RCU will disable checking upon issuing the
first warning (or "splat"). This feature prevents such
disabling, allowing multiple RCU-lockdep warnings to be printed
on a single reboot.
Say Y to allow multiple RCU-lockdep warnings per boot.
Say N if you are unsure.
config PROVE_RCU_DELAY
bool "RCU debugging: preemptible RCU race provocation"
depends on DEBUG_KERNEL && PREEMPT_RCU
default n
help
There is a class of races that involve an unlikely preemption
of __rcu_read_unlock() just after ->rcu_read_lock_nesting has
been set to INT_MIN. This feature inserts a delay at that
point to increase the probability of these races.
Say Y to increase probability of preemption of __rcu_read_unlock().
Say N if you are unsure.
config SPARSE_RCU_POINTER
bool "RCU debugging: sparse-based checks for pointer usage"
default n
help
This feature enables the __rcu sparse annotation for
RCU-protected pointers. This annotation will cause sparse
to flag any non-RCU used of annotated pointers. This can be
helpful when debugging RCU usage. Please note that this feature
is not intended to enforce code cleanliness; it is instead merely
a debugging aid.
Say Y to make sparse flag questionable use of RCU-protected pointers
Say N if you are unsure.
config RCU_TORTURE_TEST
tristate "torture tests for RCU"
depends on DEBUG_KERNEL
@ -970,7 +972,7 @@ config RCU_TORTURE_TEST_RUNNABLE
config RCU_CPU_STALL_TIMEOUT
int "RCU CPU stall timeout in seconds"
depends on TREE_RCU || TREE_PREEMPT_RCU
depends on RCU_STALL_COMMON
range 3 300
default 21
help
@ -1016,6 +1018,8 @@ config RCU_TRACE
Say Y here if you want to enable RCU tracing
Say N if you are unsure.
endmenu # "RCU Debugging"
config KPROBES_SANITY_TEST
bool "Kprobes sanity tests"
depends on DEBUG_KERNEL