From: Avi Kivity <a...@redhat.com>
Signed-off-by: Avi Kivity <a...@redhat.com>
diff --git a/external-module-compat-comm.h b/external-module-compat-comm.h
index 9801441..5b96c46 100644
--- a/external-module-compat-comm.h
+++ b/external-module-compat-comm.h
@@ -812,3 +812,16 @@ static inline struct file *eventfd_fget(int fd)
}
#endif
+
+/* srcu was born in 2.6.19 */
+
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,19)
+
+#define kvm_init_srcu_struct init_srcu_struct
+#define kvm_cleanup_srcu_struct cleanup_srcu_struct
+#define kvm_srcu_read_lock srcu_read_lock
+#define kvm_srcu_read_unlock srcu_read_unlock
+#define kvm_synchronize_srcu synchronize_srcu
+#define kvm_srcu_batches_completed srcu_batches_completed
+
+#endif
diff --git a/include-compat/linux/srcu.h b/include-compat/linux/srcu.h
new file mode 100644
index 0000000..0d476be
--- /dev/null
+++ b/include-compat/linux/srcu.h
@@ -0,0 +1,53 @@
+/*
+ * Sleepable Read-Copy Update mechanism for mutual exclusion
+ *
+ * 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 <paul...@us.ibm.com>
+ *
+ * For detailed explanation of Read-Copy Update mechanism see -
+ * Documentation/RCU/ *.txt
+ *
+ */
+
+#ifndef _LINUX_SRCU_H
+#define _LINUX_SRCU_H
+
+struct srcu_struct_array {
+ int c[2];
+};
+
+struct srcu_struct {
+ int completed;
+ struct srcu_struct_array *per_cpu_ref;
+ struct mutex mutex;
+};
+
+#ifndef CONFIG_PREEMPT
+#define srcu_barrier() barrier()
+#else /* #ifndef CONFIG_PREEMPT */
+#define srcu_barrier()
+#endif /* #else #ifndef CONFIG_PREEMPT */
+
+int kvm_init_srcu_struct(struct srcu_struct *sp);
+void kvm_cleanup_srcu_struct(struct srcu_struct *sp);
+int kvm_srcu_read_lock(struct srcu_struct *sp) __acquires(sp);
+void kvm_srcu_read_unlock(struct srcu_struct *sp, int idx) __releases(sp);
+void kvm_synchronize_srcu(struct srcu_struct *sp);
+long kvm_srcu_batches_completed(struct srcu_struct *sp);
+
+#endif
diff --git a/linux-2.6 b/linux-2.6
index 6790e2f..d789c98 160000
--- a/linux-2.6
+++ b/linux-2.6
@@ -1 +1 @@
-Subproject commit 6790e2f843585d5232ff7f724e6baf9f32cd08cd
+Subproject commit d789c98af00b1bd62f91a241586546072a41175b
diff --git a/srcu.c b/srcu.c
new file mode 100644
index 0000000..3243adf
--- /dev/null
+++ b/srcu.c
@@ -0,0 +1,263 @@
+/*
+ * Sleepable Read-Copy Update mechanism for mutual exclusion.
+ *
+ * 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 <paul...@us.ibm.com>
+ *
+ * For detailed explanation of Read-Copy Update mechanism see -
+ * Documentation/RCU/ *.txt
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/percpu.h>
+#include <linux/preempt.h>
+#include <linux/rcupdate.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/smp.h>
+#include <linux/srcu.h>
+
+#undef kvm_init_srcu_struct
+#undef kvm_cleanup_srcu_struct
+#undef kvm_srcu_read_lock
+#undef kvm_srcu_read_unlock
+#undef kvm_synchronize_srcu
+#undef kvm_srcu_batches_completed
+/**
+ * init_srcu_struct - initialize a sleep-RCU structure
+ * @sp: structure to initialize.
+ *
+ * Must invoke this on a given srcu_struct before passing that srcu_struct
+ * to any other function. Each srcu_struct represents a separate domain
+ * of SRCU protection.
+ */
+int kvm_init_srcu_struct(struct srcu_struct *sp)
+{
+ sp->completed = 0;
+ mutex_init(&sp->mutex);
+ sp->per_cpu_ref = alloc_percpu(struct srcu_struct_array);
+ return (sp->per_cpu_ref ? 0 : -ENOMEM);
+}
+
+/*
+ * srcu_readers_active_idx -- returns approximate number of readers
+ * active on the specified rank of per-CPU counters.
+ */
+
+static int srcu_readers_active_idx(struct srcu_struct *sp, int idx)
+{
+ int cpu;
+ int sum;
+
+ sum = 0;
+ for_each_possible_cpu(cpu)
+ sum += per_cpu_ptr(sp->per_cpu_ref, cpu)->c[idx];
+ return sum;
+}
+
+/**
+ * srcu_readers_active - returns approximate number of readers.
+ * @sp: which srcu_struct to count active readers (holding srcu_read_lock).
+ *
+ * Note that this is not an atomic primitive, and can therefore suffer
+ * severe errors when invoked on an active srcu_struct. That said, it
+ * can be useful as an error check at cleanup time.
+ */
+static int srcu_readers_active(struct srcu_struct *sp)
+{
+ return srcu_readers_active_idx(sp, 0) + srcu_readers_active_idx(sp, 1);
+}
+
+/**
+ * cleanup_srcu_struct - deconstruct a sleep-RCU structure
+ * @sp: structure to clean up.
+ *
+ * Must invoke this after you are finished using a given srcu_struct that
+ * was initialized via init_srcu_struct(), else you leak memory.
+ */
+void kvm_cleanup_srcu_struct(struct srcu_struct *sp)
+{
+ int sum;
+
+ sum = srcu_readers_active(sp);
+ WARN_ON(sum); /* Leakage unless caller handles error. */
+ if (sum != 0)
+ return;
+ free_percpu(sp->per_cpu_ref);
+ sp->per_cpu_ref = NULL;
+}
+
+/**
+ * srcu_read_lock - register a new reader for an SRCU-protected structure.
+ * @sp: srcu_struct in which to register the new reader.
+ *
+ * Counts the new reader in the appropriate per-CPU element of the
+ * srcu_struct. Must be called from process context.
+ * Returns an index that must be passed to the matching srcu_read_unlock().
+ */
+int kvm_srcu_read_lock(struct srcu_struct *sp)
+{
+ int idx;
+
+ preempt_disable();
+ idx = sp->completed & 0x1;
+ barrier(); /* ensure compiler looks -once- at sp->completed. */
+ per_cpu_ptr(sp->per_cpu_ref, smp_processor_id())->c[idx]++;
+ srcu_barrier(); /* ensure compiler won't misorder critical section. */
+ preempt_enable();
+ return idx;
+}
+
+/**
+ * srcu_read_unlock - unregister a old reader from an SRCU-protected structure.
+ * @sp: srcu_struct in which to unregister the old reader.
+ * @idx: return value from corresponding srcu_read_lock().
+ *
+ * Removes the count for the old reader from the appropriate per-CPU
+ * element of the srcu_struct. Note that this may well be a different
+ * CPU than that which was incremented by the corresponding srcu_read_lock().
+ * Must be called from process context.
+ */
+void kvm_srcu_read_unlock(struct srcu_struct *sp, int idx)
+{
+ preempt_disable();
+ srcu_barrier(); /* ensure compiler won't misorder critical section. */
+ per_cpu_ptr(sp->per_cpu_ref, smp_processor_id())->c[idx]--;
+ preempt_enable();
+}
+
+/**
+ * synchronize_srcu - wait for prior SRCU read-side critical-section completion
+ * @sp: srcu_struct with which to synchronize.
+ *
+ * Flip the completed counter, and wait for the old count to drain to zero.
+ * As with classic RCU, the updater must use some separate means of
+ * synchronizing concurrent updates. Can block; must be called from
+ * process context.
+ *
+ * Note that it is illegal to call synchornize_srcu() from the corresponding
+ * SRCU read-side critical section; doing so will result in deadlock.
+ * However, it is perfectly legal to call synchronize_srcu() on one
+ * srcu_struct from some other srcu_struct's read-side critical section.
+ */
+void kvm_synchronize_srcu(struct srcu_struct *sp)
+{
+ int idx;
+
+ idx = sp->completed;
+ mutex_lock(&sp->mutex);
+
+ /*
+ * Check to see if someone else did the work for us while we were
+ * waiting to acquire the lock. We need -two- advances of
+ * the counter, not just one. If there was but one, we might have
+ * shown up -after- our helper's first synchronize_sched(), thus
+ * having failed to prevent CPU-reordering races with concurrent
+ * srcu_read_unlock()s on other CPUs (see comment below). So we
+ * either (1) wait for two or (2) supply the second ourselves.
+ */
+
+ if ((sp->completed - idx) >= 2) {
+ mutex_unlock(&sp->mutex);
+ return;
+ }
+
+ synchronize_sched(); /* Force memory barrier on all CPUs. */
+
+ /*
+ * The preceding synchronize_sched() ensures that any CPU that
+ * sees the new value of sp->completed will also see any preceding
+ * changes to data structures made by this CPU. This prevents
+ * some other CPU from reordering the accesses in its SRCU
+ * read-side critical section to precede the corresponding
+ * srcu_read_lock() -- ensuring that such references will in
+ * fact be protected.
+ *
+ * So it is now safe to do the flip.
+ */
+
+ idx = sp->completed & 0x1;
+ sp->completed++;
+
+ synchronize_sched(); /* Force memory barrier on all CPUs. */
+
+ /*
+ * At this point, because of the preceding synchronize_sched(),
+ * all srcu_read_lock() calls using the old counters have completed.
+ * Their corresponding critical sections might well be still
+ * executing, but the srcu_read_lock() primitives themselves
+ * will have finished executing.
+ */
+
+ while (srcu_readers_active_idx(sp, idx))
+ schedule_timeout_interruptible(1);
+
+ synchronize_sched(); /* Force memory barrier on all CPUs. */
+
+ /*
+ * The preceding synchronize_sched() forces all srcu_read_unlock()
+ * primitives that were executing concurrently with the preceding
+ * for_each_possible_cpu() loop to have completed by this point.
+ * More importantly, it also forces the corresponding SRCU read-side
+ * critical sections to have also completed, and the corresponding
+ * references to SRCU-protected data items to be dropped.
+ *
+ * Note:
+ *
+ * Despite what you might think at first glance, the
+ * preceding synchronize_sched() -must- be within the
+ * critical section ended by the following mutex_unlock().
+ * Otherwise, a task taking the early exit can race
+ * with a srcu_read_unlock(), which might have executed
+ * just before the preceding srcu_readers_active() check,
+ * and whose CPU might have reordered the srcu_read_unlock()
+ * with the preceding critical section. In this case, there
+ * is nothing preventing the synchronize_sched() task that is
+ * taking the early exit from freeing a data structure that
+ * is still being referenced (out of order) by the task
+ * doing the srcu_read_unlock().
+ *
+ * Alternatively, the comparison with "2" on the early exit
+ * could be changed to "3", but this increases synchronize_srcu()
+ * latency for bulk loads. So the current code is preferred.
+ */
+
+ mutex_unlock(&sp->mutex);
+}
+
+/**
+ * srcu_batches_completed - return batches completed.
+ * @sp: srcu_struct on which to report batch completion.
+ *
+ * Report the number of batches, correlated with, but not necessarily
+ * precisely the same as, the number of grace periods that have elapsed.
+ */
+
+long kvm_srcu_batches_completed(struct srcu_struct *sp)
+{
+ return sp->completed;
+}
+
+EXPORT_SYMBOL_GPL(kvm_init_srcu_struct);
+EXPORT_SYMBOL_GPL(kvm_cleanup_srcu_struct);
+EXPORT_SYMBOL_GPL(kvm_srcu_read_lock);
+EXPORT_SYMBOL_GPL(kvm_srcu_read_unlock);
+EXPORT_SYMBOL_GPL(kvm_synchronize_srcu);
+EXPORT_SYMBOL_GPL(kvm_srcu_batches_completed);
diff --git a/sync b/sync
index 18f0200..c4c4078 100755
--- a/sync
+++ b/sync
@@ -34,7 +34,10 @@ def __hack(data):
'hrtimer_add_expires_ns hrtimer_get_expires '
'hrtimer_get_expires_ns hrtimer_start_expires '
'hrtimer_expires_remaining smp_send_reschedule '
- 'on_each_cpu relay_open request_irq free_irq')
+ 'on_each_cpu relay_open request_irq free_irq '
+ 'init_srcu_struct cleanup_srcu_struct srcu_read_lock '
+ 'srcu_read_unlock synchronize_srcu srcu_batches_completed '
+ )
anon_inodes = anon_inodes_exit = False
result = []
def sub(regexp, repl, str):
diff --git a/x86/Kbuild b/x86/Kbuild
index ade87fc..c4694a7 100644
--- a/x86/Kbuild
+++ b/x86/Kbuild
@@ -16,4 +16,6 @@ endif
kvm-intel-objs := vmx.o vmx-debug.o
kvm-amd-objs := svm.o
+kvm-objs += ../srcu.o
+
CFLAGS_kvm_main.o = -DKVM_MAIN
--
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