Re: [PATCH] 2.6.17-rt1 : fix x86_64 oops
From: Dipankar Sarma
Date: Wed Jul 05 2006 - 05:13:22 EST
On Tue, Jul 04, 2006 at 08:50:24AM +0200, Ingo Molnar wrote:
>
> * Ingo Molnar <mingo@xxxxxxx> wrote:
>
> > > Ingo, do you have a suspect ?
> >
> > I suspect it's the patch below. That patch (from John) relaxes the
> > affinities of IRQ threads: if there are /proc/irq/*/smp_affinity
> > entries that have multiple bits set an IRQ thread is allowed to jump
> > from one CPU to another while it is executing a IRQ-handler. It
> > _should_ be fine but i'd not be surprised if that caused breakage ...
>
> the patch below is against 2.6.17-rt5, does this solve the crashes?
>
I tried this patch but I still oops quickly after starting rcutorture.
There is some additional information - my -rt20 directory had
another patch which re-organized RCU code to cleanly have multiple
RCU implementations (rcuclassic and rcupreempt for now). That
kernel ran fine with rcutorture, but when I removed that
reorg-rcu-code patch to go to standard -rt20, I started seeing
the same oops. This is bizarre because the reorg-rcu-code
patch isn't supposed to change any logic. I am still investigating
this, but the patch is included below for your reference.
Thanks
Dipankar
This patch re-organizes the RCU code to maintain multiple implementations
of RCU. Users of RCU continues to include rcupdate.h and the
RCU interfaces remain the same.
Signed-off-by: Dipankar Sarma <dipankar@xxxxxxxxxx>
---
diff -puN /dev/null include/linux/rcuclassic.h
--- /dev/null 2006-03-26 18:34:52.000000000 +0530
+++ linux-2.6.16-rt20-rcu-dipankar/include/linux/rcuclassic.h 2006-07-04 11:33:34.000000000 +0530
@@ -0,0 +1,133 @@
+/*
+ * Read-Copy Update mechanism for mutual exclusion (classic version)
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * Copyright (C) IBM Corporation, 2001
+ *
+ * Author: Dipankar Sarma <dipankar@xxxxxxxxxx>
+ *
+ * Based on the original work by Paul McKenney <paul.mckenney@xxxxxxxxxx>
+ * 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)
+ *
+ * For detailed explanation of Read-Copy Update mechanism see -
+ * http://lse.sourceforge.net/locking/rcupdate.html
+ *
+ */
+
+#ifndef __LINUX_RCUCLASSIC_H
+#define __LINUX_RCUCLASSIC_H
+
+#ifdef __KERNEL__
+
+#include <linux/cache.h>
+#include <linux/spinlock.h>
+#include <linux/threads.h>
+#include <linux/percpu.h>
+#include <linux/cpumask.h>
+#include <linux/seqlock.h>
+
+/* Global control variables for rcupdate callback mechanism. */
+struct rcu_ctrlblk {
+ long cur; /* Current batch number. */
+ long completed; /* Number of the last completed batch */
+ int next_pending; /* Is the next batch already waiting? */
+
+ spinlock_t lock ____cacheline_internodealigned_in_smp;
+ cpumask_t cpumask; /* CPUs that need to switch in order */
+ /* for current batch to proceed. */
+} ____cacheline_internodealigned_in_smp;
+
+/* Is batch a before batch b ? */
+static inline int rcu_batch_before(long a, long b)
+{
+ return (a - b) < 0;
+}
+
+/* Is batch a after batch b ? */
+static inline int rcu_batch_after(long a, long b)
+{
+ return (a - b) > 0;
+}
+
+/*
+ * Per-CPU data for Read-Copy UPdate.
+ * nxtlist - new callbacks are added here
+ * curlist - current batch for which quiescent cycle started if any
+ */
+struct rcu_data {
+ /* 1) quiescent state handling : */
+ long quiescbatch; /* Batch # for grace period */
+ int passed_quiesc; /* User-mode/idle loop etc. */
+ int qs_pending; /* core waits for quiesc state */
+
+ /* 2) batch handling */
+ long batch; /* Batch # for current RCU batch */
+ struct rcu_head *nxtlist;
+ struct rcu_head **nxttail;
+ long qlen; /* # of queued callbacks */
+ struct rcu_head *curlist;
+ struct rcu_head **curtail;
+ struct rcu_head *donelist;
+ struct rcu_head **donetail;
+ long blimit; /* Upper limit on a processed batch */
+ int cpu;
+#ifdef CONFIG_SMP
+ long last_rs_qlen; /* qlen during the last resched */
+#endif
+};
+
+DECLARE_PER_CPU(struct rcu_data, rcu_data);
+DECLARE_PER_CPU(struct rcu_data, rcu_bh_data);
+extern struct rcu_ctrlblk rcu_ctrlblk;
+extern struct rcu_ctrlblk rcu_bh_ctrlblk;
+
+/*
+ * Increment the quiescent state counter.
+ * The counter is a bit degenerated: We do not need to know
+ * how many quiescent states passed, just if there was at least
+ * one since the start of the grace period. Thus just a flag.
+ */
+static inline void rcu_qsctr_inc(int cpu)
+{
+ struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
+ 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;
+}
+
+extern int rcu_pending(int cpu);
+
+#define __rcu_read_lock() preempt_disable()
+#define __rcu_read_unlock() preempt_enable()
+
+#define __rcu_read_lock_bh() local_bh_disable()
+#define __rcu_read_unlock_bh() local_bh_enable()
+
+#define __synchronize_sched() synchronize_rcu()
+
+extern void __rcu_init(void);
+extern void rcu_check_callbacks(int cpu, int user);
+extern void rcu_restart_cpu(int cpu);
+extern long rcu_batches_completed(void);
+
+#endif /* __KERNEL__ */
+#endif /* __LINUX_RCUCLASSIC_H */
diff -puN include/linux/rcupdate.h~reorg-rcu-code include/linux/rcupdate.h
--- linux-2.6.16-rt20-rcu/include/linux/rcupdate.h~reorg-rcu-code 2006-07-04 11:33:33.000000000 +0530
+++ linux-2.6.16-rt20-rcu-dipankar/include/linux/rcupdate.h 2006-07-04 11:33:34.000000000 +0530
@@ -42,6 +42,12 @@
#include <linux/cpumask.h>
#include <linux/seqlock.h>
+#ifdef CONFIG_CLASSIC_RCU
+#include <linux/rcuclassic.h>
+#else
+#include <linux/rcupreempt.h>
+#endif
+
/**
* struct rcu_head - callback structure for use with RCU
* @next: next update requests in a list
@@ -58,84 +64,6 @@ struct rcu_head {
(ptr)->next = NULL; (ptr)->func = NULL; \
} while (0)
-
-#ifndef CONFIG_PREEMPT_RCU
-
-/* Global control variables for rcupdate callback mechanism. */
-struct rcu_ctrlblk {
- long cur; /* Current batch number. */
- long completed; /* Number of the last completed batch */
- int next_pending; /* Is the next batch already waiting? */
-
- spinlock_t lock ____cacheline_internodealigned_in_smp;
- cpumask_t cpumask; /* CPUs that need to switch in order */
- /* for current batch to proceed. */
-} ____cacheline_internodealigned_in_smp;
-
-/* Is batch a before batch b ? */
-static inline int rcu_batch_before(long a, long b)
-{
- return (a - b) < 0;
-}
-
-/* Is batch a after batch b ? */
-static inline int rcu_batch_after(long a, long b)
-{
- return (a - b) > 0;
-}
-
-/*
- * Per-CPU data for Read-Copy UPdate.
- * nxtlist - new callbacks are added here
- * curlist - current batch for which quiescent cycle started if any
- */
-struct rcu_data {
- /* 1) quiescent state handling : */
- long quiescbatch; /* Batch # for grace period */
- int passed_quiesc; /* User-mode/idle loop etc. */
- int qs_pending; /* core waits for quiesc state */
-
- /* 2) batch handling */
- long batch; /* Batch # for current RCU batch */
- struct rcu_head *nxtlist;
- struct rcu_head **nxttail;
- long qlen; /* # of queued callbacks */
- struct rcu_head *curlist;
- struct rcu_head **curtail;
- struct rcu_head *donelist;
- struct rcu_head **donetail;
- long blimit; /* Upper limit on a processed batch */
- int cpu;
- struct rcu_head barrier;
-#ifdef CONFIG_SMP
- long last_rs_qlen; /* qlen during the last resched */
-#endif
-};
-
-DECLARE_PER_CPU(struct rcu_data, rcu_data);
-DECLARE_PER_CPU(struct rcu_data, rcu_bh_data);
-extern struct rcu_ctrlblk rcu_ctrlblk;
-extern struct rcu_ctrlblk rcu_bh_ctrlblk;
-
-/*
- * Increment the quiescent state counter.
- * The counter is a bit degenerated: We do not need to know
- * how many quiescent states passed, just if there was at least
- * one since the start of the grace period. Thus just a flag.
- */
-static inline void rcu_qsctr_inc(int cpu)
-{
- struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
- 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;
-}
-
-extern int rcu_pending(int cpu);
-
/**
* rcu_read_lock - mark the beginning of an RCU read-side critical section.
*
@@ -165,26 +93,14 @@ extern int rcu_pending(int cpu);
*
* It is illegal to block while in an RCU read-side critical section.
*/
-#define rcu_read_lock preempt_disable
+#define rcu_read_lock() __rcu_read_lock()
/**
* 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
-
-#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 */
+#define rcu_read_unlock() __rcu_read_unlock()
/*
* So where is rcu_write_lock()? It does not exist, as there is no
@@ -207,22 +123,14 @@ extern 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 */
+#define rcu_read_lock_bh() __rcu_read_lock_bh()
-/*
+/**
* 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 */
+#define rcu_read_unlock_bh() __rcu_read_unlock_bh()
/**
* rcu_dereference - fetch an RCU-protected pointer in an
@@ -274,26 +182,51 @@ extern int rcu_pending(int cpu);
* In "classic RCU", these two guarantees happen to be one and
* the same, but can differ in realtime RCU implementations.
*/
-#ifndef CONFIG_PREEMPT_RCU
-#define synchronize_sched() synchronize_rcu()
-extern void rcu_barrier(void);
-#else /* #ifndef CONFIG_PREEMPT_RCU */
-extern void synchronize_sched(void);
-#define rcu_barrier() do {} while(0)
-#endif /* #else #ifndef CONFIG_PREEMPT_RCU */
+#define synchronize_sched() __synchronize_sched()
-extern void rcu_init(void);
-extern void rcu_check_callbacks(int cpu, int user);
-extern void rcu_restart_cpu(int cpu);
-extern long rcu_batches_completed(void);
-/* Exported interfaces */
+/**
+ * call_rcu - Queue an RCU callback for invocation after a grace period.
+ * @head: structure to be used for queueing the RCU updates.
+ * @func: actual update function to be invoked after the grace period
+ *
+ * The update function will be invoked some time after a full grace
+ * period elapses, 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.
+ */
extern void FASTCALL(call_rcu(struct rcu_head *head,
void (*func)(struct rcu_head *head)));
+
+
+/**
+ * call_rcu_bh - Queue an RCU for invocation after a quicker grace period.
+ * @head: structure to be used for queueing the RCU updates.
+ * @func: actual update function to be invoked after the grace period
+ *
+ * The update function will be invoked some time after a full grace
+ * period elapses, in other words after all currently executing RCU
+ * read-side critical sections have completed. call_rcu_bh() assumes
+ * that the read-side critical sections end on completion of a softirq
+ * handler. This means that read-side critical sections in process
+ * context must not be interrupted by softirqs. This interface is to be
+ * used when most of the read-side critical sections are in softirq context.
+ * RCU read-side critical sections are delimited by rcu_read_lock() and
+ * rcu_read_unlock(), * if in interrupt context or rcu_read_lock_bh()
+ * and rcu_read_unlock_bh(), if in process context. These may be nested.
+ */
extern void FASTCALL(call_rcu_bh(struct rcu_head *head,
void (*func)(struct rcu_head *head)));
+
+/* Exported common interfaces */
+extern __deprecated_for_modules void synchronize_kernel(void);
extern void synchronize_rcu(void);
+extern void rcu_barrier(void);
void synchronize_idle(void);
+/* Internal to kernel */
+extern void rcu_init(void);
+
#endif /* __KERNEL__ */
#endif /* __LINUX_RCUPDATE_H */
diff -puN /dev/null include/linux/rcupreempt.h
--- /dev/null 2006-03-26 18:34:52.000000000 +0530
+++ linux-2.6.16-rt20-rcu-dipankar/include/linux/rcupreempt.h 2006-07-04 11:33:34.000000000 +0530
@@ -0,0 +1,66 @@
+/*
+ * Read-Copy Update mechanism for mutual exclusion (RT implementation)
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * Copyright (C) IBM Corporation, 2006
+ *
+ * Author: Paul McKenney <paulmck@xxxxxxxxxx>
+ *
+ * Based on the original work by Paul McKenney <paul.mckenney@xxxxxxxxxx>
+ * 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)
+ *
+ * For detailed explanation of Read-Copy Update mechanism see -
+ * http://lse.sourceforge.net/locking/rcupdate.html
+ *
+ */
+
+#ifndef __LINUX_RCUPREEMPT_H
+#define __LINUX_RCUPREEMPT_H
+
+#ifdef __KERNEL__
+
+#include <linux/cache.h>
+#include <linux/spinlock.h>
+#include <linux/threads.h>
+#include <linux/percpu.h>
+#include <linux/cpumask.h>
+#include <linux/seqlock.h>
+
+#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);
+
+#define __rcu_read_lock_bh() { rcu_read_lock(); local_bh_disable(); }
+#define __rcu_read_unlock_bh() { local_bh_enable(); rcu_read_unlock(); }
+
+#define __rcu_read_lock_nesting() (current->rcu_read_lock_nesting)
+
+extern void __synchronize_sched(void);
+
+extern void __rcu_init(void);
+extern void rcu_check_callbacks(int cpu, int user);
+extern void rcu_restart_cpu(int cpu);
+extern long rcu_batches_completed(void);
+
+#endif /* __KERNEL__ */
+#endif /* __LINUX_RCUPREEMPT_H */
diff -puN kernel/Kconfig.preempt~reorg-rcu-code kernel/Kconfig.preempt
--- linux-2.6.16-rt20-rcu/kernel/Kconfig.preempt~reorg-rcu-code 2006-07-04 11:33:33.000000000 +0530
+++ linux-2.6.16-rt20-rcu-dipankar/kernel/Kconfig.preempt 2006-07-04 11:33:34.000000000 +0530
@@ -155,7 +155,6 @@ config CLASSIC_RCU
config PREEMPT_RCU
bool "Preemptible RCU"
- 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
diff -puN kernel/Makefile~reorg-rcu-code kernel/Makefile
--- linux-2.6.16-rt20-rcu/kernel/Makefile~reorg-rcu-code 2006-07-04 11:33:33.000000000 +0530
+++ linux-2.6.16-rt20-rcu-dipankar/kernel/Makefile 2006-07-04 11:33:34.000000000 +0530
@@ -48,8 +48,8 @@ obj-$(CONFIG_DETECT_SOFTLOCKUP) += softl
obj-$(CONFIG_GENERIC_HARDIRQS) += irq/
obj-$(CONFIG_SECCOMP) += seccomp.o
obj-$(CONFIG_RCU_TORTURE_TEST) += rcutorture.o
-obj-$(CONFIG_CLASSIC_RCU) += rcupdate.o
-obj-$(CONFIG_PREEMPT_RCU) += rcupreempt.o
+obj-$(CONFIG_CLASSIC_RCU) += rcupdate.o rcuclassic.o
+obj-$(CONFIG_PREEMPT_RCU) += rcupdate.o rcupreempt.o
ifneq ($(CONFIG_SCHED_NO_NO_OMIT_FRAME_POINTER),y)
# According to Alan Modra <alan@xxxxxxxxxxxxxxxx>, the -fno-omit-frame-pointer is
diff -puN /dev/null kernel/rcuclassic.c
--- /dev/null 2006-03-26 18:34:52.000000000 +0530
+++ linux-2.6.16-rt20-rcu-dipankar/kernel/rcuclassic.c 2006-07-04 11:33:34.000000000 +0530
@@ -0,0 +1,511 @@
+/*
+ * Read-Copy Update mechanism for mutual exclusion, classic implementation
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * Copyright (C) IBM Corporation, 2001
+ *
+ * Authors: Dipankar Sarma <dipankar@xxxxxxxxxx>
+ * Manfred Spraul <manfred@xxxxxxxxxxxxxxxx>
+ *
+ * Based on the original work by Paul McKenney <paulmck@xxxxxxxxxx>
+ * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
+ *
+ * Papers: http://www.rdrop.com/users/paulmck/RCU
+ *
+ * For detailed explanation of Read-Copy Update mechanism see -
+ * Documentation/RCU/ *.txt
+ *
+ */
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/spinlock.h>
+#include <linux/smp.h>
+#include <linux/rcupdate.h>
+#include <linux/interrupt.h>
+#include <linux/sched.h>
+#include <asm/atomic.h>
+#include <linux/bitops.h>
+#include <linux/module.h>
+#include <linux/completion.h>
+#include <linux/moduleparam.h>
+#include <linux/percpu.h>
+#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>
+
+
+/* Definition for rcupdate control block. */
+struct rcu_ctrlblk rcu_ctrlblk = {
+ .cur = -300,
+ .completed = -300,
+ .lock = SPIN_LOCK_UNLOCKED,
+ .cpumask = CPU_MASK_NONE,
+};
+struct rcu_ctrlblk rcu_bh_ctrlblk = {
+ .cur = -300,
+ .completed = -300,
+ .lock = SPIN_LOCK_UNLOCKED,
+ .cpumask = CPU_MASK_NONE,
+};
+
+DEFINE_PER_CPU(struct rcu_data, rcu_data) = { 0L };
+DEFINE_PER_CPU(struct rcu_data, rcu_bh_data) = { 0L };
+
+/* Fake initialization required by compiler */
+static DEFINE_PER_CPU(struct tasklet_struct, rcu_tasklet) = {NULL};
+static int blimit = 10;
+static int qhimark = 10000;
+static int qlowmark = 100;
+#ifdef CONFIG_SMP
+static int rsinterval = 1000;
+#endif
+
+#ifdef CONFIG_SMP
+static void force_quiescent_state(struct rcu_data *rdp,
+ struct rcu_ctrlblk *rcp)
+{
+ int cpu;
+ cpumask_t cpumask;
+ set_need_resched();
+ if (unlikely(rdp->qlen - rdp->last_rs_qlen > rsinterval)) {
+ rdp->last_rs_qlen = rdp->qlen;
+ /*
+ * Don't send IPI to itself. With irqs disabled,
+ * rdp->cpu is the current cpu.
+ */
+ cpumask = rcp->cpumask;
+ cpu_clear(rdp->cpu, cpumask);
+ for_each_cpu_mask(cpu, cpumask)
+ smp_send_reschedule(cpu);
+ }
+}
+#else
+static inline void force_quiescent_state(struct rcu_data *rdp,
+ struct rcu_ctrlblk *rcp)
+{
+ set_need_resched();
+}
+#endif
+
+void fastcall call_rcu(struct rcu_head *head,
+ void (*func)(struct rcu_head *rcu))
+{
+ unsigned long flags;
+ struct rcu_data *rdp;
+
+ head->func = func;
+ head->next = NULL;
+ local_irq_save(flags);
+ rdp = &__get_cpu_var(rcu_data);
+ *rdp->nxttail = head;
+ rdp->nxttail = &head->next;
+ if (unlikely(++rdp->qlen > qhimark)) {
+ rdp->blimit = INT_MAX;
+ force_quiescent_state(rdp, &rcu_ctrlblk);
+ }
+ local_irq_restore(flags);
+}
+
+void fastcall call_rcu_bh(struct rcu_head *head,
+ void (*func)(struct rcu_head *rcu))
+{
+ unsigned long flags;
+ struct rcu_data *rdp;
+
+ head->func = func;
+ head->next = NULL;
+ local_irq_save(flags);
+ rdp = &__get_cpu_var(rcu_bh_data);
+ *rdp->nxttail = head;
+ rdp->nxttail = &head->next;
+
+ if (unlikely(++rdp->qlen > qhimark)) {
+ rdp->blimit = INT_MAX;
+ force_quiescent_state(rdp, &rcu_bh_ctrlblk);
+ }
+
+ local_irq_restore(flags);
+}
+
+/*
+ * Return the number of RCU batches processed thus far. Useful
+ * for debug and statistics.
+ */
+long rcu_batches_completed(void)
+{
+ return rcu_ctrlblk.completed;
+}
+
+/*
+ * Invoke the completed RCU callbacks. They are expected to be in
+ * a per-cpu list.
+ */
+static void rcu_do_batch(struct rcu_data *rdp)
+{
+ struct rcu_head *next, *list;
+ int count = 0;
+
+ list = rdp->donelist;
+ while (list) {
+ next = rdp->donelist = list->next;
+ list->func(list);
+ list = next;
+ rdp->qlen--;
+ if (++count >= rdp->blimit)
+ break;
+ }
+ if (rdp->blimit == INT_MAX && rdp->qlen <= qlowmark)
+ rdp->blimit = blimit;
+ if (!rdp->donelist)
+ rdp->donetail = &rdp->donelist;
+ else
+ tasklet_schedule(&per_cpu(rcu_tasklet, rdp->cpu));
+}
+
+/*
+ * Grace period handling:
+ * The grace period handling consists out of two steps:
+ * - A new grace period is started.
+ * This is done by rcu_start_batch. The start is not broadcasted to
+ * all cpus, they must pick this up by comparing rcp->cur with
+ * rdp->quiescbatch. All cpus are recorded in the
+ * rcu_ctrlblk.cpumask bitmap.
+ * - All cpus must go through a quiescent state.
+ * Since the start of the grace period is not broadcasted, at least two
+ * calls to rcu_check_quiescent_state are required:
+ * The first call just notices that a new grace period is running. The
+ * following calls check if there was a quiescent state since the beginning
+ * of the grace period. If so, it updates rcu_ctrlblk.cpumask. If
+ * the bitmap is empty, then the grace period is completed.
+ * rcu_check_quiescent_state calls rcu_start_batch(0) to start the next grace
+ * period (if necessary).
+ */
+/*
+ * Register a new batch of callbacks, and start it up if there is currently no
+ * active batch and the batch to be registered has not already occurred.
+ * Caller must hold rcu_ctrlblk.lock.
+ */
+static void rcu_start_batch(struct rcu_ctrlblk *rcp)
+{
+ if (rcp->next_pending &&
+ rcp->completed == rcp->cur) {
+ rcp->next_pending = 0;
+ /*
+ * next_pending == 0 must be visible in
+ * __rcu_process_callbacks() before it can see new value of cur.
+ */
+ smp_wmb();
+ rcp->cur++;
+
+ /*
+ * Accessing nohz_cpu_mask before incrementing rcp->cur needs a
+ * Barrier Otherwise it can cause tickless idle CPUs to be
+ * included in rcp->cpumask, which will extend graceperiods
+ * unnecessarily.
+ */
+ smp_mb();
+ cpus_andnot(rcp->cpumask, cpu_online_map, nohz_cpu_mask);
+
+ }
+}
+
+/*
+ * cpu went through a quiescent state since the beginning of the grace period.
+ * Clear it from the cpu mask and complete the grace period if it was the last
+ * cpu. Start another grace period if someone has further entries pending
+ */
+static void cpu_quiet(int cpu, struct rcu_ctrlblk *rcp)
+{
+ cpu_clear(cpu, rcp->cpumask);
+ if (cpus_empty(rcp->cpumask)) {
+ /* batch completed ! */
+ rcp->completed = rcp->cur;
+ rcu_start_batch(rcp);
+ }
+}
+
+/*
+ * Check if the cpu has gone through a quiescent state (say context
+ * switch). If so and if it already hasn't done so in this RCU
+ * quiescent cycle, then indicate that it has done so.
+ */
+static void rcu_check_quiescent_state(struct rcu_ctrlblk *rcp,
+ struct rcu_data *rdp)
+{
+ if (rdp->quiescbatch != rcp->cur) {
+ /* start new grace period: */
+ rdp->qs_pending = 1;
+ rdp->passed_quiesc = 0;
+ rdp->quiescbatch = rcp->cur;
+ return;
+ }
+
+ /* Grace period already completed for this cpu?
+ * qs_pending is checked instead of the actual bitmap to avoid
+ * cacheline trashing.
+ */
+ if (!rdp->qs_pending)
+ return;
+
+ /*
+ * Was there a quiescent state since the beginning of the grace
+ * period? If no, then exit and wait for the next call.
+ */
+ if (!rdp->passed_quiesc)
+ return;
+ rdp->qs_pending = 0;
+
+ spin_lock(&rcp->lock);
+ /*
+ * rdp->quiescbatch/rcp->cur and the cpu bitmap can come out of sync
+ * during cpu startup. Ignore the quiescent state.
+ */
+ if (likely(rdp->quiescbatch == rcp->cur))
+ cpu_quiet(rdp->cpu, rcp);
+
+ spin_unlock(&rcp->lock);
+}
+
+
+#ifdef CONFIG_HOTPLUG_CPU
+
+/* warning! helper for rcu_offline_cpu. do not use elsewhere without reviewing
+ * locking requirements, the list it's pulling from has to belong to a cpu
+ * which is dead and hence not processing interrupts.
+ */
+static void rcu_move_batch(struct rcu_data *this_rdp, struct rcu_head *list,
+ struct rcu_head **tail)
+{
+ local_irq_disable();
+ *this_rdp->nxttail = list;
+ if (list)
+ this_rdp->nxttail = tail;
+ local_irq_enable();
+}
+
+static void __rcu_offline_cpu(struct rcu_data *this_rdp,
+ struct rcu_ctrlblk *rcp, struct rcu_data *rdp)
+{
+ /* if the cpu going offline owns the grace period
+ * we can block indefinitely waiting for it, so flush
+ * it here
+ */
+ spin_lock_bh(&rcp->lock);
+ if (rcp->cur != rcp->completed)
+ cpu_quiet(rdp->cpu, rcp);
+ spin_unlock_bh(&rcp->lock);
+ rcu_move_batch(this_rdp, rdp->curlist, rdp->curtail);
+ rcu_move_batch(this_rdp, rdp->nxtlist, rdp->nxttail);
+ rcu_move_batch(this_rdp, rdp->donelist, rdp->donetail);
+}
+
+static void rcu_offline_cpu(int cpu)
+{
+ struct rcu_data *this_rdp = &get_cpu_var(rcu_data);
+ struct rcu_data *this_bh_rdp = &get_cpu_var(rcu_bh_data);
+
+ __rcu_offline_cpu(this_rdp, &rcu_ctrlblk,
+ &per_cpu(rcu_data, cpu));
+ __rcu_offline_cpu(this_bh_rdp, &rcu_bh_ctrlblk,
+ &per_cpu(rcu_bh_data, cpu));
+ put_cpu_var(rcu_data);
+ put_cpu_var(rcu_bh_data);
+ tasklet_kill_immediate(&per_cpu(rcu_tasklet, cpu), cpu);
+}
+
+#else
+
+static void rcu_offline_cpu(int cpu)
+{
+}
+
+#endif
+
+/*
+ * This does the RCU processing work from tasklet context.
+ */
+static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp,
+ struct rcu_data *rdp)
+{
+ if (rdp->curlist && !rcu_batch_before(rcp->completed, rdp->batch)) {
+ *rdp->donetail = rdp->curlist;
+ rdp->donetail = rdp->curtail;
+ rdp->curlist = NULL;
+ rdp->curtail = &rdp->curlist;
+ }
+
+ local_irq_disable();
+ if (rdp->nxtlist && !rdp->curlist) {
+ rdp->curlist = rdp->nxtlist;
+ rdp->curtail = rdp->nxttail;
+ rdp->nxtlist = NULL;
+ rdp->nxttail = &rdp->nxtlist;
+ local_irq_enable();
+
+ /*
+ * start the next batch of callbacks
+ */
+
+ /* determine batch number */
+ rdp->batch = rcp->cur + 1;
+ /* see the comment and corresponding wmb() in
+ * the rcu_start_batch()
+ */
+ smp_rmb();
+
+ if (!rcp->next_pending) {
+ /* and start it/schedule start if it's a new batch */
+ spin_lock(&rcp->lock);
+ rcp->next_pending = 1;
+ rcu_start_batch(rcp);
+ spin_unlock(&rcp->lock);
+ }
+ } else {
+ local_irq_enable();
+ }
+ rcu_check_quiescent_state(rcp, rdp);
+ if (rdp->donelist)
+ rcu_do_batch(rdp);
+}
+
+static void rcu_process_callbacks(unsigned long unused)
+{
+ __rcu_process_callbacks(&rcu_ctrlblk, &__get_cpu_var(rcu_data));
+ __rcu_process_callbacks(&rcu_bh_ctrlblk, &__get_cpu_var(rcu_bh_data));
+}
+
+static int __rcu_pending(struct rcu_ctrlblk *rcp, struct rcu_data *rdp)
+{
+ /* This cpu has pending rcu entries and the grace period
+ * for them has completed.
+ */
+ if (rdp->curlist && !rcu_batch_before(rcp->completed, rdp->batch))
+ return 1;
+
+ /* This cpu has no pending entries, but there are new entries */
+ if (!rdp->curlist && rdp->nxtlist)
+ return 1;
+
+ /* This cpu has finished callbacks to invoke */
+ if (rdp->donelist)
+ return 1;
+
+ /* The rcu core waits for a quiescent state from the cpu */
+ if (rdp->quiescbatch != rcp->cur || rdp->qs_pending)
+ return 1;
+
+ /* nothing to do */
+ return 0;
+}
+
+int rcu_pending(int cpu)
+{
+ return __rcu_pending(&rcu_ctrlblk, &per_cpu(rcu_data, cpu)) ||
+ __rcu_pending(&rcu_bh_ctrlblk, &per_cpu(rcu_bh_data, cpu));
+}
+
+void rcu_check_callbacks(int cpu, int user)
+{
+ if (user ||
+ (idle_cpu(cpu) && !in_softirq() &&
+ hardirq_count() <= (1 << HARDIRQ_SHIFT))) {
+ rcu_qsctr_inc(cpu);
+ rcu_bh_qsctr_inc(cpu);
+ } else if (!in_softirq())
+ rcu_bh_qsctr_inc(cpu);
+ tasklet_schedule(&per_cpu(rcu_tasklet, cpu));
+}
+
+static void rcu_init_percpu_data(int cpu, struct rcu_ctrlblk *rcp,
+ struct rcu_data *rdp)
+{
+ memset(rdp, 0, sizeof(*rdp));
+ rdp->curtail = &rdp->curlist;
+ rdp->nxttail = &rdp->nxtlist;
+ rdp->donetail = &rdp->donelist;
+ rdp->quiescbatch = rcp->completed;
+ rdp->qs_pending = 0;
+ rdp->cpu = cpu;
+ rdp->blimit = blimit;
+}
+
+static void __devinit rcu_online_cpu(int cpu)
+{
+ struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
+ struct rcu_data *bh_rdp = &per_cpu(rcu_bh_data, cpu);
+
+ rcu_init_percpu_data(cpu, &rcu_ctrlblk, rdp);
+ rcu_init_percpu_data(cpu, &rcu_bh_ctrlblk, bh_rdp);
+ tasklet_init(&per_cpu(rcu_tasklet, cpu), rcu_process_callbacks, 0UL);
+ INIT_RCU_HEAD(&per_cpu(rcu_barrier_head, cpu));
+}
+
+static int __devinit rcu_cpu_notify(struct notifier_block *self,
+ unsigned long action, void *hcpu)
+{
+ long cpu = (long)hcpu;
+ switch (action) {
+ case CPU_UP_PREPARE:
+ rcu_online_cpu(cpu);
+ break;
+ case CPU_DEAD:
+ rcu_offline_cpu(cpu);
+ break;
+ default:
+ break;
+ }
+ return NOTIFY_OK;
+}
+
+static struct notifier_block __devinitdata rcu_nb = {
+ .notifier_call = rcu_cpu_notify,
+};
+
+/*
+ * Initializes rcu mechanism. Assumed to be called early.
+ * That is before local timer(SMP) or jiffie timer (uniproc) is setup.
+ * Note that rcu_qsctr and friends are implicitly
+ * initialized due to the choice of ``0'' for RCU_CTR_INVALID.
+ */
+void __init __rcu_init(void)
+{
+ rcu_cpu_notify(&rcu_nb, CPU_UP_PREPARE,
+ (void *)(long)smp_processor_id());
+ /* Register notifier for non-boot CPUs */
+ register_cpu_notifier(&rcu_nb);
+}
+
+/*
+ * Deprecated, use synchronize_rcu() or synchronize_sched() instead.
+ */
+void synchronize_kernel(void)
+{
+ synchronize_rcu();
+}
+
+module_param(blimit, int, 0);
+module_param(qhimark, int, 0);
+module_param(qlowmark, int, 0);
+#ifdef CONFIG_SMP
+module_param(rsinterval, int, 0);
+#endif
+EXPORT_SYMBOL(call_rcu); /* WARNING: GPL-only in April 2006. */
+EXPORT_SYMBOL(call_rcu_bh); /* WARNING: GPL-only in April 2006. */
+EXPORT_SYMBOL(synchronize_kernel); /* WARNING: GPL-only in April 2006. */
diff -puN kernel/rcupdate.c~reorg-rcu-code kernel/rcupdate.c
--- linux-2.6.16-rt20-rcu/kernel/rcupdate.c~reorg-rcu-code 2006-07-04 11:33:33.000000000 +0530
+++ linux-2.6.16-rt20-rcu-dipankar/kernel/rcupdate.c 2006-07-04 11:33:34.000000000 +0530
@@ -49,140 +49,49 @@
#include <linux/random.h>
#include <linux/delay.h>
#include <linux/byteorder/swabb.h>
-#include "rcucommon.h"
-/* Definition for rcupdate control block. */
-struct rcu_ctrlblk rcu_ctrlblk = {
- .cur = -300,
- .completed = -300,
- .lock = SPIN_LOCK_UNLOCKED,
- .cpumask = CPU_MASK_NONE,
+struct rcu_synchronize {
+ struct rcu_head head;
+ struct completion completion;
};
-struct rcu_ctrlblk rcu_bh_ctrlblk = {
- .cur = -300,
- .completed = -300,
- .lock = SPIN_LOCK_UNLOCKED,
- .cpumask = CPU_MASK_NONE,
-};
-
-DEFINE_PER_CPU(struct rcu_data, rcu_data) = { 0L };
-DEFINE_PER_CPU(struct rcu_data, rcu_bh_data) = { 0L };
-
-/* Fake initialization required by compiler */
-static DEFINE_PER_CPU(struct tasklet_struct, rcu_tasklet) = {NULL};
-static int blimit = 10;
-static int qhimark = 10000;
-static int qlowmark = 100;
-#ifdef CONFIG_SMP
-static int rsinterval = 1000;
-#endif
+static DEFINE_PER_CPU(struct rcu_head, rcu_barrier_head);
static atomic_t rcu_barrier_cpu_count;
static struct semaphore rcu_barrier_sema;
static struct completion rcu_barrier_completion;
-#ifdef CONFIG_SMP
-static void force_quiescent_state(struct rcu_data *rdp,
- struct rcu_ctrlblk *rcp)
+/* Because of FASTCALL declaration of complete, we use this wrapper */
+static void wakeme_after_rcu(struct rcu_head *head)
{
- int cpu;
- cpumask_t cpumask;
- set_need_resched();
- if (unlikely(rdp->qlen - rdp->last_rs_qlen > rsinterval)) {
- rdp->last_rs_qlen = rdp->qlen;
- /*
- * Don't send IPI to itself. With irqs disabled,
- * rdp->cpu is the current cpu.
- */
- cpumask = rcp->cpumask;
- cpu_clear(rdp->cpu, cpumask);
- for_each_cpu_mask(cpu, cpumask)
- smp_send_reschedule(cpu);
- }
-}
-#else
-static inline void force_quiescent_state(struct rcu_data *rdp,
- struct rcu_ctrlblk *rcp)
-{
- set_need_resched();
+ struct rcu_synchronize *rcu;
+
+ rcu = container_of(head, struct rcu_synchronize, head);
+ complete(&rcu->completion);
}
-#endif
/**
- * call_rcu - Queue an RCU callback for invocation after a grace period.
- * @head: structure to be used for queueing the RCU updates.
- * @func: actual update function to be invoked after the grace period
+ * synchronize_rcu - wait until a grace period has elapsed.
*
- * The update function will be invoked some time after a full grace
- * period elapses, in other words after all currently executing RCU
+ * 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 fastcall call_rcu(struct rcu_head *head,
- void (*func)(struct rcu_head *rcu))
-{
- unsigned long flags;
- struct rcu_data *rdp;
-
- head->func = func;
- head->next = NULL;
- local_irq_save(flags);
- rdp = &__get_cpu_var(rcu_data);
- *rdp->nxttail = head;
- rdp->nxttail = &head->next;
- if (unlikely(++rdp->qlen > qhimark)) {
- rdp->blimit = INT_MAX;
- force_quiescent_state(rdp, &rcu_ctrlblk);
- }
- local_irq_restore(flags);
-}
-
-/**
- * call_rcu_bh - Queue an RCU for invocation after a quicker grace period.
- * @head: structure to be used for queueing the RCU updates.
- * @func: actual update function to be invoked after the grace period
*
- * The update function will be invoked some time after a full grace
- * period elapses, in other words after all currently executing RCU
- * read-side critical sections have completed. call_rcu_bh() assumes
- * that the read-side critical sections end on completion of a softirq
- * handler. This means that read-side critical sections in process
- * context must not be interrupted by softirqs. This interface is to be
- * used when most of the read-side critical sections are in softirq context.
- * RCU read-side critical sections are delimited by rcu_read_lock() and
- * rcu_read_unlock(), * if in interrupt context or rcu_read_lock_bh()
- * and rcu_read_unlock_bh(), if in process context. These may be nested.
+ * If your read-side code is not protected by rcu_read_lock(), do -not-
+ * use synchronize_rcu().
*/
-void fastcall call_rcu_bh(struct rcu_head *head,
- void (*func)(struct rcu_head *rcu))
+void synchronize_rcu(void)
{
- unsigned long flags;
- struct rcu_data *rdp;
+ struct rcu_synchronize rcu;
+
+ init_completion(&rcu.completion);
+ /* Will wake me after RCU finished */
+ call_rcu(&rcu.head, wakeme_after_rcu);
- head->func = func;
- head->next = NULL;
- local_irq_save(flags);
- rdp = &__get_cpu_var(rcu_bh_data);
- *rdp->nxttail = head;
- rdp->nxttail = &head->next;
-
- if (unlikely(++rdp->qlen > qhimark)) {
- rdp->blimit = INT_MAX;
- force_quiescent_state(rdp, &rcu_bh_ctrlblk);
- }
-
- local_irq_restore(flags);
-}
-
-/*
- * Return the number of RCU batches processed thus far. Useful
- * for debug and statistics.
- */
-long rcu_batches_completed(void)
-{
- return rcu_ctrlblk.completed;
+ /* Wait for it */
+ wait_for_completion(&rcu.completion);
}
static void rcu_barrier_callback(struct rcu_head *notused)
@@ -197,10 +106,8 @@ static void rcu_barrier_callback(struct
static void rcu_barrier_func(void *notused)
{
int cpu = smp_processor_id();
- struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
- struct rcu_head *head;
+ struct rcu_head *head = &per_cpu(rcu_barrier_head, cpu);
- head = &rdp->barrier;
atomic_inc(&rcu_barrier_cpu_count);
call_rcu(head, rcu_barrier_callback);
}
@@ -219,353 +126,12 @@ void rcu_barrier(void)
wait_for_completion(&rcu_barrier_completion);
up(&rcu_barrier_sema);
}
-EXPORT_SYMBOL_GPL(rcu_barrier);
-
-/*
- * Invoke the completed RCU callbacks. They are expected to be in
- * a per-cpu list.
- */
-static void rcu_do_batch(struct rcu_data *rdp)
-{
- struct rcu_head *next, *list;
- int count = 0;
-
- list = rdp->donelist;
- while (list) {
- next = rdp->donelist = list->next;
- list->func(list);
- list = next;
- rdp->qlen--;
- if (++count >= rdp->blimit)
- break;
- }
- if (rdp->blimit == INT_MAX && rdp->qlen <= qlowmark)
- rdp->blimit = blimit;
- if (!rdp->donelist)
- rdp->donetail = &rdp->donelist;
- else
- tasklet_schedule(&per_cpu(rcu_tasklet, rdp->cpu));
-}
-
-/*
- * Grace period handling:
- * The grace period handling consists out of two steps:
- * - A new grace period is started.
- * This is done by rcu_start_batch. The start is not broadcasted to
- * all cpus, they must pick this up by comparing rcp->cur with
- * rdp->quiescbatch. All cpus are recorded in the
- * rcu_ctrlblk.cpumask bitmap.
- * - All cpus must go through a quiescent state.
- * Since the start of the grace period is not broadcasted, at least two
- * calls to rcu_check_quiescent_state are required:
- * The first call just notices that a new grace period is running. The
- * following calls check if there was a quiescent state since the beginning
- * of the grace period. If so, it updates rcu_ctrlblk.cpumask. If
- * the bitmap is empty, then the grace period is completed.
- * rcu_check_quiescent_state calls rcu_start_batch(0) to start the next grace
- * period (if necessary).
- */
-/*
- * Register a new batch of callbacks, and start it up if there is currently no
- * active batch and the batch to be registered has not already occurred.
- * Caller must hold rcu_ctrlblk.lock.
- */
-static void rcu_start_batch(struct rcu_ctrlblk *rcp)
-{
- if (rcp->next_pending &&
- rcp->completed == rcp->cur) {
- rcp->next_pending = 0;
- /*
- * next_pending == 0 must be visible in
- * __rcu_process_callbacks() before it can see new value of cur.
- */
- smp_wmb();
- rcp->cur++;
-
- /*
- * Accessing nohz_cpu_mask before incrementing rcp->cur needs a
- * Barrier Otherwise it can cause tickless idle CPUs to be
- * included in rcp->cpumask, which will extend graceperiods
- * unnecessarily.
- */
- smp_mb();
- cpus_andnot(rcp->cpumask, cpu_online_map, nohz_cpu_mask);
-
- }
-}
-
-/*
- * cpu went through a quiescent state since the beginning of the grace period.
- * Clear it from the cpu mask and complete the grace period if it was the last
- * cpu. Start another grace period if someone has further entries pending
- */
-static void cpu_quiet(int cpu, struct rcu_ctrlblk *rcp)
-{
- cpu_clear(cpu, rcp->cpumask);
- if (cpus_empty(rcp->cpumask)) {
- /* batch completed ! */
- rcp->completed = rcp->cur;
- rcu_start_batch(rcp);
- }
-}
-
-/*
- * Check if the cpu has gone through a quiescent state (say context
- * switch). If so and if it already hasn't done so in this RCU
- * quiescent cycle, then indicate that it has done so.
- */
-static void rcu_check_quiescent_state(struct rcu_ctrlblk *rcp,
- struct rcu_data *rdp)
-{
- if (rdp->quiescbatch != rcp->cur) {
- /* start new grace period: */
- rdp->qs_pending = 1;
- rdp->passed_quiesc = 0;
- rdp->quiescbatch = rcp->cur;
- return;
- }
-
- /* Grace period already completed for this cpu?
- * qs_pending is checked instead of the actual bitmap to avoid
- * cacheline trashing.
- */
- if (!rdp->qs_pending)
- return;
-
- /*
- * Was there a quiescent state since the beginning of the grace
- * period? If no, then exit and wait for the next call.
- */
- if (!rdp->passed_quiesc)
- return;
- rdp->qs_pending = 0;
-
- spin_lock(&rcp->lock);
- /*
- * rdp->quiescbatch/rcp->cur and the cpu bitmap can come out of sync
- * during cpu startup. Ignore the quiescent state.
- */
- if (likely(rdp->quiescbatch == rcp->cur))
- cpu_quiet(rdp->cpu, rcp);
-
- spin_unlock(&rcp->lock);
-}
-
-#ifdef CONFIG_HOTPLUG_CPU
-
-/* warning! helper for rcu_offline_cpu. do not use elsewhere without reviewing
- * locking requirements, the list it's pulling from has to belong to a cpu
- * which is dead and hence not processing interrupts.
- */
-static void rcu_move_batch(struct rcu_data *this_rdp, struct rcu_head *list,
- struct rcu_head **tail)
-{
- local_irq_disable();
- *this_rdp->nxttail = list;
- if (list)
- this_rdp->nxttail = tail;
- local_irq_enable();
-}
-
-static void __rcu_offline_cpu(struct rcu_data *this_rdp,
- struct rcu_ctrlblk *rcp, struct rcu_data *rdp)
-{
- /* if the cpu going offline owns the grace period
- * we can block indefinitely waiting for it, so flush
- * it here
- */
- spin_lock_bh(&rcp->lock);
- if (rcp->cur != rcp->completed)
- cpu_quiet(rdp->cpu, rcp);
- spin_unlock_bh(&rcp->lock);
- rcu_move_batch(this_rdp, rdp->curlist, rdp->curtail);
- rcu_move_batch(this_rdp, rdp->nxtlist, rdp->nxttail);
- rcu_move_batch(this_rdp, rdp->donelist, rdp->donetail);
-}
-
-static void rcu_offline_cpu(int cpu)
-{
- struct rcu_data *this_rdp = &get_cpu_var(rcu_data);
- struct rcu_data *this_bh_rdp = &get_cpu_var(rcu_bh_data);
-
- __rcu_offline_cpu(this_rdp, &rcu_ctrlblk,
- &per_cpu(rcu_data, cpu));
- __rcu_offline_cpu(this_bh_rdp, &rcu_bh_ctrlblk,
- &per_cpu(rcu_bh_data, cpu));
- put_cpu_var(rcu_data);
- put_cpu_var(rcu_bh_data);
- tasklet_kill_immediate(&per_cpu(rcu_tasklet, cpu), cpu);
-}
-
-#else
-
-static void rcu_offline_cpu(int cpu)
-{
-}
-
-#endif
-
-/*
- * This does the RCU processing work from tasklet context.
- */
-static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp,
- struct rcu_data *rdp)
-{
- if (rdp->curlist && !rcu_batch_before(rcp->completed, rdp->batch)) {
- *rdp->donetail = rdp->curlist;
- rdp->donetail = rdp->curtail;
- rdp->curlist = NULL;
- rdp->curtail = &rdp->curlist;
- }
-
- local_irq_disable();
- if (rdp->nxtlist && !rdp->curlist) {
- rdp->curlist = rdp->nxtlist;
- rdp->curtail = rdp->nxttail;
- rdp->nxtlist = NULL;
- rdp->nxttail = &rdp->nxtlist;
- local_irq_enable();
-
- /*
- * start the next batch of callbacks
- */
-
- /* determine batch number */
- rdp->batch = rcp->cur + 1;
- /* see the comment and corresponding wmb() in
- * the rcu_start_batch()
- */
- smp_rmb();
-
- if (!rcp->next_pending) {
- /* and start it/schedule start if it's a new batch */
- spin_lock(&rcp->lock);
- rcp->next_pending = 1;
- rcu_start_batch(rcp);
- spin_unlock(&rcp->lock);
- }
- } else {
- local_irq_enable();
- }
- rcu_check_quiescent_state(rcp, rdp);
- if (rdp->donelist)
- rcu_do_batch(rdp);
-}
-
-static void rcu_process_callbacks(unsigned long unused)
-{
- __rcu_process_callbacks(&rcu_ctrlblk, &__get_cpu_var(rcu_data));
- __rcu_process_callbacks(&rcu_bh_ctrlblk, &__get_cpu_var(rcu_bh_data));
-}
-
-static int __rcu_pending(struct rcu_ctrlblk *rcp, struct rcu_data *rdp)
-{
- /* This cpu has pending rcu entries and the grace period
- * for them has completed.
- */
- if (rdp->curlist && !rcu_batch_before(rcp->completed, rdp->batch))
- return 1;
-
- /* This cpu has no pending entries, but there are new entries */
- if (!rdp->curlist && rdp->nxtlist)
- return 1;
-
- /* This cpu has finished callbacks to invoke */
- if (rdp->donelist)
- return 1;
-
- /* The rcu core waits for a quiescent state from the cpu */
- if (rdp->quiescbatch != rcp->cur || rdp->qs_pending)
- return 1;
-
- /* nothing to do */
- return 0;
-}
-
-int rcu_pending(int cpu)
-{
- return __rcu_pending(&rcu_ctrlblk, &per_cpu(rcu_data, cpu)) ||
- __rcu_pending(&rcu_bh_ctrlblk, &per_cpu(rcu_bh_data, cpu));
-}
-
-void rcu_check_callbacks(int cpu, int user)
-{
- if (user ||
- (idle_cpu(cpu) && !in_softirq() &&
- hardirq_count() <= (1 << HARDIRQ_SHIFT))) {
- rcu_qsctr_inc(cpu);
- rcu_bh_qsctr_inc(cpu);
- } else if (!in_softirq())
- rcu_bh_qsctr_inc(cpu);
- tasklet_schedule(&per_cpu(rcu_tasklet, cpu));
-}
-
-static void rcu_init_percpu_data(int cpu, struct rcu_ctrlblk *rcp,
- struct rcu_data *rdp)
-{
- memset(rdp, 0, sizeof(*rdp));
- rdp->curtail = &rdp->curlist;
- rdp->nxttail = &rdp->nxtlist;
- rdp->donetail = &rdp->donelist;
- rdp->quiescbatch = rcp->completed;
- rdp->qs_pending = 0;
- rdp->cpu = cpu;
- rdp->blimit = blimit;
-}
-
-static void __devinit rcu_online_cpu(int cpu)
-{
- struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
- struct rcu_data *bh_rdp = &per_cpu(rcu_bh_data, cpu);
-
- rcu_init_percpu_data(cpu, &rcu_ctrlblk, rdp);
- rcu_init_percpu_data(cpu, &rcu_bh_ctrlblk, bh_rdp);
- tasklet_init(&per_cpu(rcu_tasklet, cpu), rcu_process_callbacks, 0UL);
-}
-
-static int __devinit rcu_cpu_notify(struct notifier_block *self,
- unsigned long action, void *hcpu)
-{
- long cpu = (long)hcpu;
- switch (action) {
- case CPU_UP_PREPARE:
- rcu_online_cpu(cpu);
- break;
- case CPU_DEAD:
- rcu_offline_cpu(cpu);
- break;
- default:
- break;
- }
- return NOTIFY_OK;
-}
-
-static struct notifier_block __devinitdata rcu_nb = {
- .notifier_call = rcu_cpu_notify,
-};
-
-/*
- * Initializes rcu mechanism. Assumed to be called early.
- * That is before local timer(SMP) or jiffie timer (uniproc) is setup.
- * Note that rcu_qsctr and friends are implicitly
- * initialized due to the choice of ``0'' for RCU_CTR_INVALID.
- */
void __init rcu_init(void)
{
sema_init(&rcu_barrier_sema, 1);
- rcu_cpu_notify(&rcu_nb, CPU_UP_PREPARE,
- (void *)(long)smp_processor_id());
- /* Register notifier for non-boot CPUs */
- register_cpu_notifier(&rcu_nb);
+ __rcu_init();
}
-module_param(blimit, int, 0);
-module_param(qhimark, int, 0);
-module_param(qlowmark, int, 0);
-#ifdef CONFIG_SMP
-module_param(rsinterval, int, 0);
-#endif
-EXPORT_SYMBOL_GPL(call_rcu);
-EXPORT_SYMBOL_GPL(call_rcu_bh);
EXPORT_SYMBOL_GPL(synchronize_rcu);
+EXPORT_SYMBOL_GPL(rcu_barrier);
diff -puN kernel/rcupreempt.c~reorg-rcu-code kernel/rcupreempt.c
--- linux-2.6.16-rt20-rcu/kernel/rcupreempt.c~reorg-rcu-code 2006-07-04 11:33:34.000000000 +0530
+++ linux-2.6.16-rt20-rcu-dipankar/kernel/rcupreempt.c 2006-07-04 11:33:34.000000000 +0530
@@ -46,7 +46,6 @@
#include <linux/random.h>
#include <linux/delay.h>
#include <linux/byteorder/swabb.h>
-#include "rcucommon.h"
/*
* PREEMPT_RCU data structures.
@@ -101,8 +100,7 @@ long rcu_batches_completed(void)
return rcu_ctrlblk.completed;
}
-void
-rcu_read_lock(void)
+void __rcu_read_lock(void)
{
int flipctr;
unsigned long oldirq;
@@ -146,8 +144,7 @@ rcu_read_lock(void)
local_irq_restore(oldirq);
}
-void
-rcu_read_unlock(void)
+void __rcu_read_unlock(void)
{
unsigned long oldirq;
@@ -172,8 +169,7 @@ rcu_read_unlock(void)
local_irq_restore(oldirq);
}
-static void
-__rcu_advance_callbacks(void)
+static void __rcu_advance_callbacks(void)
{
if (rcu_data.completed != rcu_ctrlblk.completed) {
@@ -213,8 +209,7 @@ __rcu_advance_callbacks(void)
* on a large SMP, they might want to use a hierarchical organization of
* the per-CPU-counter pairs.
*/
-static void
-rcu_try_flip(void)
+static void rcu_try_flip(void)
{
int cpu;
long flipctr;
@@ -271,8 +266,7 @@ rcu_try_flip(void)
spin_unlock_irqrestore(&rcu_ctrlblk.fliplock, oldirq);
}
-void
-rcu_check_callbacks(int cpu, int user)
+void rcu_check_callbacks(int cpu, int user)
{
unsigned long oldirq;
@@ -295,8 +289,7 @@ rcu_check_callbacks(int cpu, int user)
}
}
-static
-void rcu_process_callbacks(unsigned long data)
+static void rcu_process_callbacks(unsigned long data)
{
unsigned long flags;
struct rcu_head *next, *list;
@@ -324,9 +317,8 @@ void rcu_process_callbacks(unsigned long
}
}
-void fastcall
-call_rcu(struct rcu_head *head,
- void (*func)(struct rcu_head *rcu))
+void fastcall call_rcu(struct rcu_head *head,
+ void (*func)(struct rcu_head *rcu))
{
unsigned long flags;
@@ -349,8 +341,7 @@ call_rcu(struct rcu_head *head,
* switch to eliminate possibility of failure. (Maybe just crank
* priority down...)
*/
-void
-synchronize_sched(void)
+void __synchronize_sched(void)
{
cpumask_t oldmask;
int cpu;
@@ -365,15 +356,14 @@ synchronize_sched(void)
sched_setaffinity(0, oldmask);
}
-int
-rcu_pending(int cpu)
+int rcu_pending(int cpu)
{
return (rcu_data.donelist != NULL ||
rcu_data.waitlist != NULL ||
rcu_data.nextlist != NULL);
}
-void __init rcu_init(void)
+void __init __rcu_init(void)
{
/*&&&&*/printk("WARNING: experimental RCU implementation.\n");
spin_lock_init(&rcu_data.lock);
@@ -457,6 +447,6 @@ int rcu_read_proc_ctrs_data(char *page)
EXPORT_SYMBOL_GPL(call_rcu);
EXPORT_SYMBOL_GPL(rcu_batches_completed);
EXPORT_SYMBOL_GPL(synchronize_rcu);
-EXPORT_SYMBOL_GPL(synchronize_sched);
-EXPORT_SYMBOL_GPL(rcu_read_lock);
-EXPORT_SYMBOL_GPL(rcu_read_unlock);
+EXPORT_SYMBOL_GPL(__synchronize_sched);
+EXPORT_SYMBOL_GPL(__rcu_read_lock);
+EXPORT_SYMBOL_GPL(__rcu_read_unlock);
diff -puN -L kernel/rcucommon.h kernel/rcucommon.h~reorg-rcu-code /dev/null
--- linux-2.6.16-rt20-rcu/kernel/rcucommon.h
+++ /dev/null 2006-03-26 18:34:52.000000000 +0530
@@ -1,71 +0,0 @@
-/*
- * Read-Copy Update mechanism for mutual exclusion, definitions common
- * to all implementations.
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
- *
- * Copyright (C) IBM Corporation, 2001
- *
- * Authors: Dipankar Sarma <dipankar@xxxxxxxxxx>
- * Manfred Spraul <manfred@xxxxxxxxxxxxxxxx>
- * Paul E. McKenney <paulmck@xxxxxxxxxx>
- *
- * Based on the original work by Paul McKenney <paulmck@xxxxxxxxxx>
- * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
- *
- * Papers: http://www.rdrop.com/users/paulmck/RCU
- *
- * For detailed explanation of Read-Copy Update mechanism see -
- * Documentation/RCU/ *.txt
- *
- */
-
-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);
-}
_
-
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