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SubjectRe: [RFC,PATCH] RCU and CONFIG_PREEMPT_RT sane patch

* Paul E. McKenney <paulmck@us.ibm.com> wrote:

> Hello!
>
> The attached patch passes 20 hours of the internal-to-RCU torture test
> (see the code in the attached patch under CONFIG_RCU_TORTURE_TEST),
> which is a good improvement over last week's version, which would fail
> this test in less than two seconds -- this despite passing kernbench
> with flying colors and passing LTP 90% of the time. Sometimes there
> is no substitute for a good in-kernel stress test...
>
> The attached version of the patch seems to me to be ready for a larger
> audience.

Cool! I've merged your patch to the -52-12 version of the -RT patch. You
can get it from the usual place:

http://redhat.com/~mingo/realtime-preempt/

also, i've attached a port against 2.6.13-rc4. I have done this because
the PREEMPT_RCU patch in my tree is applied before the core-PREEMPT_RT
patch. I have fixed up the CONFIG_PREEMPT compilation branch and have
removed your #error define - it built and booted fine on an UP box but
there are no guarantees ...

Ingo

make rcu_read_lock() critical sections preemptible.

fs/proc/proc_misc.c | 81 ++++
include/linux/rcupdate.h | 50 ++-
include/linux/sched.h | 5
kernel/Kconfig.preempt | 36 ++
kernel/rcupdate.c | 783 +++++++++++++++++++++++++++++++++++++++++++++--
5 files changed, 918 insertions(+), 37 deletions(-)

Index: linux/fs/proc/proc_misc.c
===================================================================
--- linux.orig/fs/proc/proc_misc.c
+++ linux/fs/proc/proc_misc.c
@@ -563,6 +563,78 @@ void create_seq_entry(char *name, mode_t
entry->proc_fops = f;
}

+#ifdef CONFIG_RCU_STATS
+int rcu_read_proc(char *page, char **start, off_t off,
+ int count, int *eof, void *data)
+{
+ int len;
+ extern int rcu_read_proc_data(char *page);
+
+ len = rcu_read_proc_data(page);
+ return proc_calc_metrics(page, start, off, count, eof, len);
+}
+
+int rcu_read_proc_gp(char *page, char **start, off_t off,
+ int count, int *eof, void *data)
+{
+ int len;
+ extern int rcu_read_proc_gp_data(char *page);
+
+ len = rcu_read_proc_gp_data(page);
+ return proc_calc_metrics(page, start, off, count, eof, len);
+}
+
+int rcu_read_proc_ptrs(char *page, char **start, off_t off,
+ int count, int *eof, void *data)
+{
+ int len;
+ extern int rcu_read_proc_ptrs_data(char *page);
+
+ len = rcu_read_proc_ptrs_data(page);
+ return proc_calc_metrics(page, start, off, count, eof, len);
+}
+
+int rcu_read_proc_ctrs(char *page, char **start, off_t off,
+ int count, int *eof, void *data)
+{
+ int len;
+ extern int rcu_read_proc_ctrs_data(char *page);
+
+ len = rcu_read_proc_ctrs_data(page);
+ return proc_calc_metrics(page, start, off, count, eof, len);
+}
+
+int rcu_read_proc_torture_writer(char *page, char **start, off_t off,
+ int count, int *eof, void *data)
+{
+ int len;
+ extern int rcu_read_proc_torture_writer_data(char *page);
+
+ len = rcu_read_proc_torture_writer_data(page);
+ return proc_calc_metrics(page, start, off, count, eof, len);
+}
+
+int rcu_read_proc_torture_reader(char *page, char **start, off_t off,
+ int count, int *eof, void *data)
+{
+ int len;
+ extern int rcu_read_proc_torture_reader_data(char *page);
+
+ len = rcu_read_proc_torture_reader_data(page);
+ return proc_calc_metrics(page, start, off, count, eof, len);
+}
+
+int rcu_read_proc_torture_stats(char *page, char **start, off_t off,
+ int count, int *eof, void *data)
+{
+ int len;
+ extern int rcu_read_proc_torture_stats_data(char *page);
+
+ len = rcu_read_proc_torture_stats_data(page);
+ return proc_calc_metrics(page, start, off, count, eof, len);
+}
+#endif /* #ifdef CONFIG_RCU_STATS */
+
void __init proc_misc_init(void)
{
struct proc_dir_entry *entry;
@@ -585,6 +657,15 @@ void __init proc_misc_init(void)
{"cmdline", cmdline_read_proc},
{"locks", locks_read_proc},
{"execdomains", execdomains_read_proc},
+#ifdef CONFIG_RCU_STATS
+ {"rcustats", rcu_read_proc},
+ {"rcugp", rcu_read_proc_gp},
+ {"rcuptrs", rcu_read_proc_ptrs},
+ {"rcuctrs", rcu_read_proc_ctrs},
+ {"rcutw", rcu_read_proc_torture_writer},
+ {"rcutr", rcu_read_proc_torture_reader},
+ {"rcuts", rcu_read_proc_torture_stats},
+#endif /* #ifdef CONFIG_RCU_STATS */
{NULL,}
};
for (p = simple_ones; p->name; p++)
Index: linux/include/linux/rcupdate.h
===================================================================
--- linux.orig/include/linux/rcupdate.h
+++ linux/include/linux/rcupdate.h
@@ -59,6 +59,7 @@ struct rcu_head {
} while (0)


+#ifndef CONFIG_PREEMPT_RCU

/* Global control variables for rcupdate callback mechanism. */
struct rcu_ctrlblk {
@@ -99,6 +100,9 @@ struct rcu_data {
struct rcu_head *donelist;
struct rcu_head **donetail;
int cpu;
+#ifdef CONFIG_PREEMPT_RCU
+ atomic_t active_readers;
+#endif
};

DECLARE_PER_CPU(struct rcu_data, rcu_data);
@@ -115,12 +119,18 @@ extern struct rcu_ctrlblk rcu_bh_ctrlblk
static inline void rcu_qsctr_inc(int cpu)
{
struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
- rdp->passed_quiesc = 1;
+#ifdef CONFIG_PREEMPT_RCU
+ if (!atomic_read(&rdp->active_readers))
+#endif
+ rdp->passed_quiesc = 1;
}
static inline void rcu_bh_qsctr_inc(int cpu)
{
struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu);
- rdp->passed_quiesc = 1;
+#ifdef CONFIG_PREEMPT_RCU
+ if (!atomic_read(&rdp->active_readers))
+#endif
+ rdp->passed_quiesc = 1;
}

static inline int __rcu_pending(struct rcu_ctrlblk *rcp,
@@ -183,14 +193,34 @@ static inline int rcu_pending(int cpu)
*
* It is illegal to block while in an RCU read-side critical section.
*/
-#define rcu_read_lock() preempt_disable()
+#ifdef CONFIG_PREEMPT_RCU
+ extern void rcu_read_lock(void);
+#else
+# define rcu_read_lock preempt_disable
+#endif

/**
* rcu_read_unlock - marks the end of an RCU read-side critical section.
*
* See rcu_read_lock() for more information.
*/
-#define rcu_read_unlock() preempt_enable()
+#ifdef CONFIG_PREEMPT_RCU
+ extern void rcu_read_unlock(void);
+#else
+# define rcu_read_unlock preempt_enable
+#endif
+
+#else /* #ifndef CONFIG_PREEMPT_RCU */
+
+#define rcu_qsctr_inc(cpu)
+#define rcu_bh_qsctr_inc(cpu)
+#define call_rcu_bh(head, rcu) call_rcu(head, rcu)
+
+extern void rcu_read_lock(void);
+extern void rcu_read_unlock(void);
+extern int rcu_pending(int cpu);
+
+#endif /* #else #ifndef CONFIG_PREEMPT_RCU */

/*
* So where is rcu_write_lock()? It does not exist, as there is no
@@ -213,14 +243,22 @@ static inline int rcu_pending(int cpu)
* can use just rcu_read_lock().
*
*/
+#ifndef CONFIG_PREEMPT_RCU
#define rcu_read_lock_bh() local_bh_disable()
+#else /* #ifndef CONFIG_PREEMPT_RCU */
+#define rcu_read_lock_bh() { rcu_read_lock(); local_bh_disable(); }
+#endif /* #else #ifndef CONFIG_PREEMPT_RCU */

/*
* rcu_read_unlock_bh - marks the end of a softirq-only RCU critical section
*
* See rcu_read_lock_bh() for more information.
*/
+#ifndef CONFIG_PREEMPT_RCU
#define rcu_read_unlock_bh() local_bh_enable()
+#else /* #ifndef CONFIG_PREEMPT_RCU */
+#define rcu_read_unlock_bh() { local_bh_enable(); rcu_read_unlock(); }
+#endif /* #else #ifndef CONFIG_PREEMPT_RCU */

/**
* rcu_dereference - fetch an RCU-protected pointer in an
@@ -269,7 +307,11 @@ static inline int rcu_pending(int cpu)
* synchronize_kernel() API. In contrast, synchronize_rcu() only
* guarantees that rcu_read_lock() sections will have completed.
*/
+#ifndef CONFIG_PREEMPT_RCU
#define synchronize_sched() synchronize_rcu()
+#else /* #ifndef CONFIG_PREEMPT_RCU */
+extern void synchronize_sched(void);
+#endif /* #else #ifndef CONFIG_PREEMPT_RCU */

extern void rcu_init(void);
extern void rcu_check_callbacks(int cpu, int user);
Index: linux/include/linux/sched.h
===================================================================
--- linux.orig/include/linux/sched.h
+++ linux/include/linux/sched.h
@@ -623,6 +623,11 @@ struct task_struct {
cpumask_t cpus_allowed;
unsigned int time_slice, first_time_slice;

+#ifdef CONFIG_PREEMPT_RCU
+ int rcu_read_lock_nesting;
+ atomic_t *rcu_flipctr1;
+ atomic_t *rcu_flipctr2;
+#endif
#ifdef CONFIG_SCHEDSTATS
struct sched_info sched_info;
#endif
Index: linux/kernel/Kconfig.preempt
===================================================================
--- linux.orig/kernel/Kconfig.preempt
+++ linux/kernel/Kconfig.preempt
@@ -63,3 +63,39 @@ config PREEMPT_BKL
Say Y here if you are building a kernel for a desktop system.
Say N if you are unsure.

+config PREEMPT_RCU
+ bool "Preemptible RCU"
+ default n
+ depends on PREEMPT
+ help
+ This option reduces the latency of the kernel by making certain
+ RCU sections preemptible. Normally RCU code is non-preemptible, if
+ this option is selected then read-only RCU sections become
+ preemptible. This helps latency, but may expose bugs due to
+ now-naive assumptions about each RCU read-side critical section
+ remaining on a given CPU through its execution.
+
+ Say N if you are unsure.
+
+config RCU_STATS
+ bool "/proc stats for preemptible RCU read-side critical sections"
+ depends on PREEMPT_RCU
+ default y
+ help
+ This option provides /proc stats to provide debugging info for
+ the preemptible realtime RCU implementation.
+
+ Say Y here if you want to see RCU stats in /proc
+ Say N if you are unsure.
+
+config RCU_TORTURE_TEST
+ bool "/proc torture tests for RCU"
+ depends on RCU_STATS
+ default y
+ help
+ This option provides /proc files that run torture tests on
+ the preemptible realtime RCU implementation.
+
+ Say Y here if you want to be able to run RCU torture tests.
+ Say N if you are unsure.
+
Index: linux/kernel/rcupdate.c
===================================================================
--- linux.orig/kernel/rcupdate.c
+++ linux/kernel/rcupdate.c
@@ -19,15 +19,15 @@
*
* Authors: Dipankar Sarma <dipankar@in.ibm.com>
* Manfred Spraul <manfred@colorfullife.com>
+ * Paul E. McKenney <paulmck@us.ibm.com> (PREEMPT_RCU)
*
* Based on the original work by Paul McKenney <paulmck@us.ibm.com>
* and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
- * Papers:
- * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf
- * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001)
+ *
+ * Papers: http://www.rdrop.com/users/paulmck/RCU
*
* For detailed explanation of Read-Copy Update mechanism see -
- * http://lse.sourceforge.net/locking/rcupdate.html
+ * Documentation/RCU/ *.txt
*
*/
#include <linux/types.h>
@@ -46,6 +46,49 @@
#include <linux/notifier.h>
#include <linux/rcupdate.h>
#include <linux/cpu.h>
+#include <linux/random.h>
+#include <linux/delay.h>
+#include <linux/byteorder/swabb.h>
+
+struct rcu_synchronize {
+ struct rcu_head head;
+ struct completion completion;
+};
+
+/* Because of FASTCALL declaration of complete, we use this wrapper */
+static void wakeme_after_rcu(struct rcu_head *head)
+{
+ struct rcu_synchronize *rcu;
+
+ rcu = container_of(head, struct rcu_synchronize, head);
+ complete(&rcu->completion);
+}
+
+/**
+ * synchronize_rcu - wait until a grace period has elapsed.
+ *
+ * Control will return to the caller some time after a full grace
+ * period has elapsed, in other words after all currently executing RCU
+ * read-side critical sections have completed. RCU read-side critical
+ * sections are delimited by rcu_read_lock() and rcu_read_unlock(),
+ * and may be nested.
+ *
+ * If your read-side code is not protected by rcu_read_lock(), do -not-
+ * use synchronize_rcu().
+ */
+void synchronize_rcu(void)
+{
+ struct rcu_synchronize rcu;
+
+ init_completion(&rcu.completion);
+ /* Will wake me after RCU finished */
+ call_rcu(&rcu.head, wakeme_after_rcu);
+
+ /* Wait for it */
+ wait_for_completion(&rcu.completion);
+}
+
+#ifndef CONFIG_PREEMPT_RCU

/* Definition for rcupdate control block. */
struct rcu_ctrlblk rcu_ctrlblk =
@@ -429,42 +472,395 @@ void __init rcu_init(void)
register_cpu_notifier(&rcu_nb);
}

-struct rcu_synchronize {
- struct rcu_head head;
- struct completion completion;
+/*
+ * Deprecated, use synchronize_rcu() or synchronize_sched() instead.
+ */
+void synchronize_kernel(void)
+{
+ synchronize_rcu();
+}
+
+module_param(maxbatch, int, 0);
+EXPORT_SYMBOL(call_rcu); /* WARNING: GPL-only in April 2006. */
+EXPORT_SYMBOL(call_rcu_bh); /* WARNING: GPL-only in April 2006. */
+EXPORT_SYMBOL_GPL(synchronize_rcu);
+EXPORT_SYMBOL(synchronize_kernel); /* WARNING: GPL-only in April 2006. */
+
+#else /* #ifndef CONFIG_PREEMPT_RCU */
+
+#ifndef CONFIG_PREEMPT_RT
+# define raw_spinlock_t spinlock_t
+# define RAW_SPIN_LOCK_UNLOCKED SPIN_LOCK_UNLOCKED
+# define raw_local_irq_save local_irq_save
+# define raw_local_irq_restore local_irq_restore
+#endif /* #ifndef CONFIG_PREEMPT_RT */
+
+struct rcu_data {
+ raw_spinlock_t lock;
+ long batch;
+ struct tasklet_struct rcu_tasklet;
+ struct rcu_head *nextlist;
+ struct rcu_head **nexttail;
+ struct rcu_head *waitlist;
+ struct rcu_head **waittail;
+ struct rcu_head *donelist;
+ struct rcu_head **donetail;
+#ifdef CONFIG_RCU_STATS
+ long n_next_length;
+ long n_next_add;
+ long n_wait_length;
+ long n_wait_add;
+ long n_done_length;
+ long n_done_add;
+ long n_done_remove;
+ atomic_t n_done_invoked;
+ long n_rcu_check_callbacks;
+ atomic_t n_synchronize_rcu;
+ atomic_t n_rcu_try_flip1;
+ long n_rcu_try_flip2;
+ long n_rcu_try_flip3;
+ atomic_t n_rcu_try_flip_e1;
+ long n_rcu_try_flip_e2;
+ long n_rcu_try_flip_e3;
+#ifdef CONFIG_RCU_TORTURE_TEST
+ atomic_t n_rcu_torture_alloc;
+ atomic_t n_rcu_torture_alloc_fail;
+ atomic_t n_rcu_torture_free;
+#endif /* #ifdef CONFIG_RCU_TORTURE_TEST */
+#endif /* #ifdef CONFIG_RCU_STATS */
+};
+struct rcu_ctrlblk {
+ raw_spinlock_t fliplock;
+ long batch;
+};
+static struct rcu_data rcu_data;
+static struct rcu_ctrlblk rcu_ctrlblk = {
+ .fliplock = RAW_SPIN_LOCK_UNLOCKED,
+ .batch = 0,
};
+static DEFINE_PER_CPU(atomic_t [2], rcu_flipctr) =
+ { ATOMIC_INIT(0), ATOMIC_INIT(0) };

-/* Because of FASTCALL declaration of complete, we use this wrapper */
-static void wakeme_after_rcu(struct rcu_head *head)
+#ifdef CONFIG_RCU_TORTURE_TEST
+
+#define RCU_TORTURE_PIPE_LEN 10
+
+struct rcu_torture {
+ struct rcu_head rtort_rcu;
+ int rtort_pipe_count;
+ struct list_head rtort_free;
+};
+
+static LIST_HEAD(rcu_torture_freelist);
+static struct rcu_torture *rcu_torture_current = NULL;
+static long rcu_torture_current_version = 0;
+static struct rcu_torture rcu_tortures[10 * RCU_TORTURE_PIPE_LEN];
+static DEFINE_SPINLOCK(rcu_torture_lock);
+static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_count) =
+ { 0 };
+static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_batch) =
+ { 0 };
+static atomic_t rcu_torture_wcount[RCU_TORTURE_PIPE_LEN + 1] =
+ { ATOMIC_INIT(0) };
+#define RCU_TORTURE_NOWRITER 0
+#define RCU_TORTURE_WRITERACTIVE 1
+#define RCU_TORTURE_STOPWRITER 2
+static int rcu_torture_wstatus = RCU_TORTURE_NOWRITER;
+
+#endif /* #ifdef CONFIG_RCU_TORTURE_TEST */
+
+void
+rcu_read_lock(void)
{
- struct rcu_synchronize *rcu;
+ int flipctr;
+ unsigned long oldirq;

- rcu = container_of(head, struct rcu_synchronize, head);
- complete(&rcu->completion);
+ raw_local_irq_save(oldirq);
+ if (current->rcu_read_lock_nesting++ == 0) {
+
+ /*
+ * Outermost nesting of rcu_read_lock(), so atomically
+ * increment the current counter for the current CPU.
+ */
+
+ flipctr = rcu_ctrlblk.batch & 0x1;
+ smp_read_barrier_depends();
+ current->rcu_flipctr1 = &(__get_cpu_var(rcu_flipctr)[flipctr]);
+ /* Can optimize to non-atomic on fastpath, but start simple. */
+ atomic_inc(current->rcu_flipctr1);
+ smp_mb__after_atomic_inc(); /* might optimize out... */
+ if (unlikely(flipctr != (rcu_ctrlblk.batch & 0x1))) {
+
+ /*
+ * We raced with grace-period processing (flip).
+ * Although we cannot be preempted here, there
+ * could be interrupts, ECC errors and the like,
+ * so just nail down both sides of the rcu_flipctr
+ * array for the duration of our RCU read-side
+ * critical section, preventing a second flip
+ * from racing with us. At some point, it would
+ * be safe to decrement one of the counters, but
+ * we have no way of knowing when that would be.
+ * So just decrement them both in rcu_read_unlock().
+ */
+
+ current->rcu_flipctr2 =
+ &(__get_cpu_var(rcu_flipctr)[!flipctr]);
+ /* Can again optimize to non-atomic on fastpath. */
+ atomic_inc(current->rcu_flipctr2);
+ smp_mb__after_atomic_inc(); /* might optimize out... */
+ }
+ }
+ raw_local_irq_restore(oldirq);
}

-/**
- * synchronize_rcu - wait until a grace period has elapsed.
- *
- * Control will return to the caller some time after a full grace
- * period has elapsed, in other words after all currently executing RCU
- * read-side critical sections have completed. RCU read-side critical
- * sections are delimited by rcu_read_lock() and rcu_read_unlock(),
- * and may be nested.
+void
+rcu_read_unlock(void)
+{
+ unsigned long oldirq;
+
+ raw_local_irq_save(oldirq);
+ if (--current->rcu_read_lock_nesting == 0) {
+
+ /*
+ * Just atomically decrement whatever we incremented.
+ * Might later want to awaken some task waiting for the
+ * grace period to complete, but keep it simple for the
+ * moment.
+ */
+
+ smp_mb__before_atomic_dec();
+ atomic_dec(current->rcu_flipctr1);
+ current->rcu_flipctr1 = NULL;
+ if (unlikely(current->rcu_flipctr2 != NULL)) {
+ atomic_dec(current->rcu_flipctr2);
+ current->rcu_flipctr2 = NULL;
+ }
+ }
+ raw_local_irq_restore(oldirq);
+}
+
+static void
+__rcu_advance_callbacks(void)
+{
+
+ if (rcu_data.batch != rcu_ctrlblk.batch) {
+ if (rcu_data.waitlist != NULL) {
+ *rcu_data.donetail = rcu_data.waitlist;
+ rcu_data.donetail = rcu_data.waittail;
+#ifdef CONFIG_RCU_STATS
+ rcu_data.n_done_length += rcu_data.n_wait_length;
+ rcu_data.n_done_add += rcu_data.n_wait_length;
+ rcu_data.n_wait_length = 0;
+#endif /* #ifdef CONFIG_RCU_STATS */
+ }
+ if (rcu_data.nextlist != NULL) {
+ rcu_data.waitlist = rcu_data.nextlist;
+ rcu_data.waittail = rcu_data.nexttail;
+ rcu_data.nextlist = NULL;
+ rcu_data.nexttail = &rcu_data.nextlist;
+#ifdef CONFIG_RCU_STATS
+ rcu_data.n_wait_length += rcu_data.n_next_length;
+ rcu_data.n_wait_add += rcu_data.n_next_length;
+ rcu_data.n_next_length = 0;
+#endif /* #ifdef CONFIG_RCU_STATS */
+ } else {
+ rcu_data.waitlist = NULL;
+ rcu_data.waittail = &rcu_data.waitlist;
+ }
+ rcu_data.batch = rcu_ctrlblk.batch;
+ }
+}
+
+/*
+ * Attempt a single flip of the counters. Remember, a single flip does
+ * -not- constitute a grace period. Instead, the interval between
+ * a pair of consecutive flips is a grace period.
*
- * If your read-side code is not protected by rcu_read_lock(), do -not-
- * use synchronize_rcu().
+ * If anyone is nuts enough to run this CONFIG_PREEMPT_RCU implementation
+ * on a large SMP, they might want to use a hierarchical organization of
+ * the per-CPU-counter pairs.
*/
-void synchronize_rcu(void)
+static void
+rcu_try_flip(void)
{
- struct rcu_synchronize rcu;
+ int cpu;
+ long flipctr;
+ unsigned long oldirq;
+
+ flipctr = rcu_ctrlblk.batch;
+#ifdef CONFIG_RCU_STATS
+ atomic_inc(&rcu_data.n_rcu_try_flip1);
+#endif /* #ifdef CONFIG_RCU_STATS */
+ if (unlikely(!spin_trylock_irqsave(&rcu_ctrlblk.fliplock, oldirq))) {
+#ifdef CONFIG_RCU_STATS
+ atomic_inc(&rcu_data.n_rcu_try_flip_e1);
+#endif /* #ifdef CONFIG_RCU_STATS */
+ return;
+ }
+ if (unlikely(flipctr != rcu_ctrlblk.batch)) {
+
+ /* Our work is done! ;-) */
+
+#ifdef CONFIG_RCU_STATS
+ rcu_data.n_rcu_try_flip_e2++;
+#endif /* #ifdef CONFIG_RCU_STATS */
+ spin_unlock_irqrestore(&rcu_ctrlblk.fliplock, oldirq);
+ return;
+ }
+ flipctr &= 0x1;

- init_completion(&rcu.completion);
- /* Will wake me after RCU finished */
- call_rcu(&rcu.head, wakeme_after_rcu);
+ /*
+ * Check for completion of all RCU read-side critical sections
+ * that started prior to the previous flip.
+ */

- /* Wait for it */
- wait_for_completion(&rcu.completion);
+#ifdef CONFIG_RCU_STATS
+ rcu_data.n_rcu_try_flip2++;
+#endif /* #ifdef CONFIG_RCU_STATS */
+ for_each_cpu(cpu) {
+ if (atomic_read(&per_cpu(rcu_flipctr, cpu)[!flipctr]) != 0) {
+#ifdef CONFIG_RCU_STATS
+ rcu_data.n_rcu_try_flip_e3++;
+#endif /* #ifdef CONFIG_RCU_STATS */
+ spin_unlock_irqrestore(&rcu_ctrlblk.fliplock, oldirq);
+ return;
+ }
+ }
+
+ /* Do the flip. */
+
+ smp_mb();
+ rcu_ctrlblk.batch++;
+
+#ifdef CONFIG_RCU_STATS
+ rcu_data.n_rcu_try_flip3++;
+#endif /* #ifdef CONFIG_RCU_STATS */
+ spin_unlock_irqrestore(&rcu_ctrlblk.fliplock, oldirq);
+}
+
+void
+rcu_check_callbacks(int cpu, int user)
+{
+ unsigned long oldirq;
+
+ if (rcu_ctrlblk.batch == rcu_data.batch) {
+ rcu_try_flip();
+ if (rcu_ctrlblk.batch == rcu_data.batch) {
+ return;
+ }
+ }
+ spin_lock_irqsave(&rcu_data.lock, oldirq);
+#ifdef CONFIG_RCU_STATS
+ rcu_data.n_rcu_check_callbacks++;
+#endif /* #ifdef CONFIG_RCU_STATS */
+ __rcu_advance_callbacks();
+ if (rcu_data.donelist == NULL) {
+ spin_unlock_irqrestore(&rcu_data.lock, oldirq);
+ } else {
+ spin_unlock_irqrestore(&rcu_data.lock, oldirq);
+ tasklet_schedule(&rcu_data.rcu_tasklet);
+ }
+}
+
+static
+void rcu_process_callbacks(unsigned long data)
+{
+ unsigned long flags;
+ struct rcu_head *next, *list;
+
+ spin_lock_irqsave(&rcu_data.lock, flags);
+ list = rcu_data.donelist;
+ if (list == NULL) {
+ spin_unlock_irqrestore(&rcu_data.lock, flags);
+ return;
+ }
+ rcu_data.donelist = NULL;
+ rcu_data.donetail = &rcu_data.donelist;
+#ifdef CONFIG_RCU_STATS
+ rcu_data.n_done_remove += rcu_data.n_done_length;
+ rcu_data.n_done_length = 0;
+#endif /* #ifdef CONFIG_RCU_STATS */
+ spin_unlock_irqrestore(&rcu_data.lock, flags);
+ while (list) {
+ next = list->next;
+ list->func(list);
+ list = next;
+#ifdef CONFIG_RCU_STATS
+ atomic_inc(&rcu_data.n_done_invoked);
+#endif /* #ifdef CONFIG_RCU_STATS */
+ }
+}
+
+void fastcall
+call_rcu(struct rcu_head *head,
+ void (*func)(struct rcu_head *rcu))
+{
+ unsigned long flags;
+
+ head->func = func;
+ head->next = NULL;
+ spin_lock_irqsave(&rcu_data.lock, flags);
+ __rcu_advance_callbacks();
+ *rcu_data.nexttail = head;
+ rcu_data.nexttail = &head->next;
+#ifdef CONFIG_RCU_STATS
+ rcu_data.n_next_add++;
+ rcu_data.n_next_length++;
+#endif /* #ifdef CONFIG_RCU_STATS */
+ spin_unlock_irqrestore(&rcu_data.lock, flags);
+}
+
+/*
+ * Crude hack, reduces but does not eliminate possibility of failure.
+ * Needs to wait for all CPUs to pass through a -voluntary- context
+ * switch to eliminate possibility of failure. (Maybe just crank
+ * priority down...)
+ */
+void
+synchronize_sched(void)
+{
+ cpumask_t oldmask;
+ int cpu;
+
+ if (sched_getaffinity(0, &oldmask) < 0) {
+ oldmask = cpu_possible_map;
+ }
+ for_each_cpu(cpu) {
+ sched_setaffinity(0, cpumask_of_cpu(cpu));
+ schedule();
+ }
+ sched_setaffinity(0, oldmask);
+}
+
+int
+rcu_pending(int cpu)
+{
+ return (rcu_data.donelist != NULL ||
+ rcu_data.waitlist != NULL ||
+ rcu_data.nextlist != NULL);
+}
+
+void __init rcu_init(void)
+{
+#ifdef CONFIG_RCU_TORTURE_TEST
+ int i;
+
+ for (i = 0; i < sizeof(rcu_tortures) / sizeof(rcu_tortures[0]); i++) {
+ list_add_tail(&rcu_tortures[i].rtort_free,
+ &rcu_torture_freelist);
+ }
+#endif /* #ifdef CONFIG_RCU_TORTURE_TEST */
+/*&&&&*/printk("WARNING: experimental RCU implementation.\n");
+ rcu_data.lock = RAW_SPIN_LOCK_UNLOCKED;
+ rcu_data.batch = 0;
+ rcu_data.nextlist = NULL;
+ rcu_data.nexttail = &rcu_data.nextlist;
+ rcu_data.waitlist = NULL;
+ rcu_data.waittail = &rcu_data.waitlist;
+ rcu_data.donelist = NULL;
+ rcu_data.donetail = &rcu_data.donelist;
+ tasklet_init(&rcu_data.rcu_tasklet, rcu_process_callbacks, 0UL);
}

/*
@@ -475,8 +871,329 @@ void synchronize_kernel(void)
synchronize_rcu();
}

-module_param(maxbatch, int, 0);
-EXPORT_SYMBOL(call_rcu); /* WARNING: GPL-only in April 2006. */
-EXPORT_SYMBOL(call_rcu_bh); /* WARNING: GPL-only in April 2006. */
+#ifdef CONFIG_RCU_STATS
+int rcu_read_proc_data(char *page)
+{
+ return sprintf(page,
+ "ggp=%ld lgp=%ld sr=%d rcc=%ld\n"
+ "na=%ld nl=%ld wa=%ld wl=%ld dl=%ld dr=%ld di=%d\n"
+ "rtf1=%d rtf2=%ld rtf3=%ld rtfe1=%d rtfe2=%ld rtfe3=%ld\n",
+
+ rcu_ctrlblk.batch,
+ rcu_data.batch,
+ atomic_read(&rcu_data.n_synchronize_rcu),
+ rcu_data.n_rcu_check_callbacks,
+
+ rcu_data.n_next_add,
+ rcu_data.n_next_length,
+ rcu_data.n_wait_add,
+ rcu_data.n_wait_length,
+ rcu_data.n_done_length,
+ rcu_data.n_done_remove,
+ atomic_read(&rcu_data.n_done_invoked),
+
+ atomic_read(&rcu_data.n_rcu_try_flip1),
+ rcu_data.n_rcu_try_flip2,
+ rcu_data.n_rcu_try_flip3,
+ atomic_read(&rcu_data.n_rcu_try_flip_e1),
+ rcu_data.n_rcu_try_flip_e2,
+ rcu_data.n_rcu_try_flip_e3);
+}
+
+int rcu_read_proc_gp_data(char *page)
+{
+ long oldgp = rcu_ctrlblk.batch;
+
+ synchronize_rcu();
+ return sprintf(page, "oldggp=%ld newggp=%ld\n",
+ oldgp, rcu_ctrlblk.batch);
+}
+
+int rcu_read_proc_ptrs_data(char *page)
+{
+ return sprintf(page,
+ "nl=%p/%p nt=%p\n wl=%p/%p wt=%p dl=%p/%p dt=%p\n",
+ &rcu_data.nextlist, rcu_data.nextlist, rcu_data.nexttail,
+ &rcu_data.waitlist, rcu_data.waitlist, rcu_data.waittail,
+ &rcu_data.donelist, rcu_data.donelist, rcu_data.donetail
+ );
+}
+
+int rcu_read_proc_ctrs_data(char *page)
+{
+ int cnt = 0;
+ int cpu;
+ int f = rcu_data.batch & 0x1;
+
+ cnt += sprintf(&page[cnt], "CPU last cur\n");
+ for_each_cpu(cpu) {
+ cnt += sprintf(&page[cnt], "%3d %4d %3d\n",
+ cpu,
+ atomic_read(&per_cpu(rcu_flipctr, cpu)[!f]),
+ atomic_read(&per_cpu(rcu_flipctr, cpu)[f]));
+ }
+ cnt += sprintf(&page[cnt], "ggp = %ld\n", rcu_data.batch);
+ return (cnt);
+}
+
+#ifdef CONFIG_RCU_TORTURE_TEST
+
+/*
+ * Allocate an element from the rcu_tortures pool.
+ */
+struct rcu_torture *
+rcu_torture_alloc(void)
+{
+ struct list_head *p;
+
+ spin_lock(&rcu_torture_lock);
+ if (list_empty(&rcu_torture_freelist)) {
+#ifdef CONFIG_RCU_STATS
+ atomic_inc(&rcu_data.n_rcu_torture_alloc_fail);
+#endif /* #ifdef CONFIG_RCU_STATS */
+ spin_unlock(&rcu_torture_lock);
+ return (NULL);
+ }
+#ifdef CONFIG_RCU_STATS
+ atomic_inc(&rcu_data.n_rcu_torture_alloc);
+#endif /* #ifdef CONFIG_RCU_STATS */
+ p = rcu_torture_freelist.next;
+ list_del_init(p);
+ spin_unlock(&rcu_torture_lock);
+ return (container_of(p, struct rcu_torture, rtort_free));
+}
+
+/*
+ * Free an element to the rcu_tortures pool.
+ */
+void
+rcu_torture_free(struct rcu_torture *p)
+{
+#ifdef CONFIG_RCU_STATS
+ atomic_inc(&rcu_data.n_rcu_torture_free);
+#endif /* #ifdef CONFIG_RCU_STATS */
+ spin_lock(&rcu_torture_lock);
+ list_add_tail(&p->rtort_free, &rcu_torture_freelist);
+ spin_unlock(&rcu_torture_lock);
+}
+
+void
+rcu_torture_cb(struct rcu_head *p)
+{
+ int i;
+ struct rcu_torture *rp = container_of(p, struct rcu_torture, rtort_rcu);
+
+#ifdef CONFIG_RCU_STATS
+ i = rp->rtort_pipe_count;
+ if (i > RCU_TORTURE_PIPE_LEN) {
+ i = RCU_TORTURE_PIPE_LEN;
+ }
+ atomic_inc(&rcu_torture_wcount[i]);
+#endif /* #ifdef CONFIG_RCU_STATS */
+ if (++rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) {
+ rcu_torture_free(rp);
+ } else {
+ call_rcu(p, rcu_torture_cb);
+ }
+}
+
+struct rcu_random_state {
+ unsigned long rrs_state;
+ unsigned long rrs_count;
+};
+
+#define RCU_RANDOM_MULT 39916801 /* prime */
+#define RCU_RANDOM_ADD 479001701 /* prime */
+#define RCU_RANDOM_REFRESH 10000
+
+#define DEFINE_RCU_RANDOM(name) struct rcu_random_state name = { 0, 0 }
+
+/*
+ * Crude but fast random-number generator. Uses a linear congruential
+ * generator, with occasional help from get_random_bytes().
+ */
+static long
+rcu_random(struct rcu_random_state *rrsp)
+{
+ long refresh;
+
+ if (--rrsp->rrs_count < 0) {
+ get_random_bytes(&refresh, sizeof(refresh));
+ rrsp->rrs_state += refresh;
+ rrsp->rrs_count = RCU_RANDOM_REFRESH;
+ }
+ rrsp->rrs_state = rrsp->rrs_state * RCU_RANDOM_MULT + RCU_RANDOM_ADD;
+ return (swahw32(rrsp->rrs_state));
+}
+
+/*
+ * Handles /proc/rcutw. Unusual in that the user must cat /proc/rcutw
+ * a second time to allow the first read of /proc/rcutw to complete.
+ * Only one writer may be in existence at a time.
+ */
+int
+rcu_read_proc_torture_writer_data(char *page)
+{
+ int i;
+ long oldbatch = rcu_ctrlblk.batch;
+ struct rcu_torture *rp;
+ struct rcu_torture *old_rp;
+ static DEFINE_RCU_RANDOM(rand);
+
+ spin_lock(&rcu_torture_lock);
+ if (rcu_torture_wstatus == RCU_TORTURE_WRITERACTIVE) {
+ rcu_torture_wstatus = RCU_TORTURE_STOPWRITER;
+ spin_unlock(&rcu_torture_lock);
+ return sprintf(page, "Terminating prior /proc/rcutw test.\n");
+ } else if (rcu_torture_wstatus == RCU_TORTURE_STOPWRITER) {
+ spin_unlock(&rcu_torture_lock);
+ return sprintf(page, "Wait for prior /proc/rcutw test.\n");
+ } else if (rcu_torture_wstatus != RCU_TORTURE_NOWRITER) {
+ return sprintf(page, "Unexpected rcu_torture_wstatus = %d",
+ rcu_torture_wstatus);
+ }
+ rcu_torture_wstatus = RCU_TORTURE_WRITERACTIVE;
+ spin_unlock(&rcu_torture_lock);
+ while (rcu_torture_wstatus == RCU_TORTURE_WRITERACTIVE) {
+ set_current_state(TASK_UNINTERRUPTIBLE);
+ schedule_timeout(1);
+ if (rcu_ctrlblk.batch == oldbatch) {
+ continue;
+ }
+ if ((rp = rcu_torture_alloc()) == NULL) {
+ continue;
+ }
+ rp->rtort_pipe_count = 0;
+ udelay(rcu_random(&rand) & 0x3ff);
+ old_rp = rcu_torture_current;
+ rcu_assign_pointer(rcu_torture_current, rp);
+ smp_wmb();
+ if (old_rp != NULL) {
+#ifdef CONFIG_RCU_STATS
+ i = old_rp->rtort_pipe_count;
+ if (i > RCU_TORTURE_PIPE_LEN) {
+ i = RCU_TORTURE_PIPE_LEN;
+ }
+ atomic_inc(&rcu_torture_wcount[i]);
+#endif /* #ifdef CONFIG_RCU_STATS */
+ old_rp->rtort_pipe_count++;
+ call_rcu(&old_rp->rtort_rcu, rcu_torture_cb);
+ }
+ rcu_torture_current_version++;
+ oldbatch = rcu_ctrlblk.batch;
+ }
+
+ spin_lock(&rcu_torture_lock);
+ rcu_torture_wstatus = RCU_TORTURE_NOWRITER;
+ spin_unlock(&rcu_torture_lock);
+
+ return sprintf(page, "End of /proc/rcutw\n");
+}
+
+/*
+ * Handles /proc/rcutr. Unusual in that the user must send a signal
+ * to the process to allow the read to complete. Multiple readers
+ * may run in parallel, but each must be sent a separate signal to
+ * stop.
+ */
+int
+rcu_read_proc_torture_reader_data(char *page)
+{
+ int batch;
+ DEFINE_RCU_RANDOM(rand);
+ struct rcu_torture *p;
+ int pipe_count;
+
+ while (!signal_pending(current)) {
+ rcu_read_lock();
+ batch = rcu_ctrlblk.batch;
+ p = rcu_torture_current;
+ if (p == NULL) {
+ rcu_read_unlock();
+ return sprintf(page, "Need to do /proc/rcutw!\n");
+ }
+ udelay(rcu_random(&rand) & 0x7f);
+ preempt_disable();
+ pipe_count = p->rtort_pipe_count;
+ if (pipe_count > RCU_TORTURE_PIPE_LEN) {
+ /* Should not happen, but... */
+ pipe_count = RCU_TORTURE_PIPE_LEN;
+ }
+ ++__get_cpu_var(rcu_torture_count)[pipe_count];
+ batch = rcu_ctrlblk.batch - batch;
+ if (batch > RCU_TORTURE_PIPE_LEN) {
+ /* Should not happen, but... */
+ batch = RCU_TORTURE_PIPE_LEN;
+ }
+ ++__get_cpu_var(rcu_torture_batch)[batch];
+ preempt_enable();
+ rcu_read_unlock();
+ schedule();
+ }
+ return sprintf(page, "End of /proc/rcutr\n");
+}
+
+/*
+ * Handles /proc/rcuts, printing out counts of how long readers were
+ * allowed to look at RCU-protected data structures.
+ */
+int
+rcu_read_proc_torture_stats_data(char *page)
+{
+ int cnt = 0;
+ int cpu;
+ int i;
+ long pipesummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
+ long batchsummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
+
+ for_each_cpu(cpu) {
+ for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
+ pipesummary[i] += per_cpu(rcu_torture_count, cpu)[i];
+ batchsummary[i] += per_cpu(rcu_torture_batch, cpu)[i];
+ }
+ }
+ for (i = RCU_TORTURE_PIPE_LEN - 1; i >= 0; i--) {
+ if (pipesummary[i] != 0) {
+ break;
+ }
+ }
+ cnt += sprintf(&page[cnt],
+ "rtc: %p ver: %ld tfle: %d rta: %d rtaf: %d rtf: %d\n",
+ rcu_torture_current,
+ rcu_torture_current_version,
+ list_empty(&rcu_torture_freelist),
+ atomic_read(&rcu_data.n_rcu_torture_alloc),
+ atomic_read(&rcu_data.n_rcu_torture_alloc_fail),
+ atomic_read(&rcu_data.n_rcu_torture_free));
+ if (i > 1) {
+ cnt += sprintf(&page[cnt], "!!! ");
+ }
+ cnt += sprintf(&page[cnt], "Reader Pipe: ");
+ for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
+ cnt += sprintf(&page[cnt], " %ld", pipesummary[i]);
+ }
+ cnt += sprintf(&page[cnt], "\nReader Batch: ");
+ for (i = 0; i < RCU_TORTURE_PIPE_LEN; i++) {
+ cnt += sprintf(&page[cnt], " %ld", batchsummary[i]);
+ }
+ cnt += sprintf(&page[cnt], "\nFree-Block Circulation: ");
+ for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
+ cnt += sprintf(&page[cnt], " %d",
+ atomic_read(&rcu_torture_wcount[i]));
+ }
+ cnt += sprintf(&page[cnt], "\n");
+ return (cnt);
+
+}
+
+#endif /* #ifdef CONFIG_RCU_TORTURE_TEST */
+#endif /* #ifdef CONFIG_RCU_STATS */
+
+EXPORT_SYMBOL(call_rcu); /* WARNING: GPL-only in April 2006. */
EXPORT_SYMBOL_GPL(synchronize_rcu);
-EXPORT_SYMBOL(synchronize_kernel); /* WARNING: GPL-only in April 2006. */
+EXPORT_SYMBOL_GPL(synchronize_sched);
+EXPORT_SYMBOL(rcu_read_lock); /* WARNING: GPL-only in April 2006. */
+EXPORT_SYMBOL(rcu_read_unlock); /* WARNING: GPL-only in April 2006. */
+EXPORT_SYMBOL(synchronize_kernel); /* WARNING: Removal in April 2006. */
+
+#endif /* #else #ifndef CONFIG_PREEMPT_RCU */
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