[Feature][T106]ZXW P56U09 code
Only Configure: Yes
Affected branch: master
Affected module: unknow
Is it affected on both ZXIC and MTK: only ZXIC
Self-test: No
Doc Update: No
Change-Id: I3cbd8b420271eb20c2b40ebe5c78f83059cd42f3
diff --git a/ap/os/linux/linux-3.4.x/kernel/srcu.c b/ap/os/linux/linux-3.4.x/kernel/srcu.c
new file mode 100644
index 0000000..ba35f3a
--- /dev/null
+++ b/ap/os/linux/linux-3.4.x/kernel/srcu.c
@@ -0,0 +1,328 @@
+/*
+ * 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 <paulmck@us.ibm.com>
+ *
+ * For detailed explanation of Read-Copy Update mechanism see -
+ * Documentation/RCU/ *.txt
+ *
+ */
+
+#include <linux/export.h>
+#include <linux/mutex.h>
+#include <linux/percpu.h>
+#include <linux/preempt.h>
+#include <linux/rcupdate.h>
+#include <linux/sched.h>
+#include <linux/smp.h>
+#include <linux/delay.h>
+#include <linux/srcu.h>
+
+static int init_srcu_struct_fields(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;
+}
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+
+int __init_srcu_struct(struct srcu_struct *sp, const char *name,
+ struct lock_class_key *key)
+{
+ /* Don't re-initialize a lock while it is held. */
+ debug_check_no_locks_freed((void *)sp, sizeof(*sp));
+ lockdep_init_map(&sp->dep_map, name, key, 0);
+ return init_srcu_struct_fields(sp);
+}
+EXPORT_SYMBOL_GPL(__init_srcu_struct);
+
+#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
+
+/**
+ * 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 init_srcu_struct(struct srcu_struct *sp)
+{
+ return init_srcu_struct_fields(sp);
+}
+EXPORT_SYMBOL_GPL(init_srcu_struct);
+
+#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
+
+/*
+ * 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 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;
+}
+EXPORT_SYMBOL_GPL(cleanup_srcu_struct);
+
+/*
+ * 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 __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;
+}
+EXPORT_SYMBOL_GPL(__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 __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();
+}
+EXPORT_SYMBOL_GPL(__srcu_read_unlock);
+
+/*
+ * We use an adaptive strategy for synchronize_srcu() and especially for
+ * synchronize_srcu_expedited(). We spin for a fixed time period
+ * (defined below) to allow SRCU readers to exit their read-side critical
+ * sections. If there are still some readers after 10 microseconds,
+ * we repeatedly block for 1-millisecond time periods. This approach
+ * has done well in testing, so there is no need for a config parameter.
+ */
+#define SYNCHRONIZE_SRCU_READER_DELAY 10
+
+/*
+ * Helper function for synchronize_srcu() and synchronize_srcu_expedited().
+ */
+static void __synchronize_srcu(struct srcu_struct *sp, void (*sync_func)(void))
+{
+ int idx;
+
+ rcu_lockdep_assert(!lock_is_held(&sp->dep_map) &&
+ !lock_is_held(&rcu_bh_lock_map) &&
+ !lock_is_held(&rcu_lock_map) &&
+ !lock_is_held(&rcu_sched_lock_map),
+ "Illegal synchronize_srcu() in same-type SRCU (or RCU) read-side critical section");
+
+ 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;
+ }
+
+ sync_func(); /* 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++;
+
+ sync_func(); /* 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. We initially give readers
+ * an arbitrarily chosen 10 microseconds to get out of their
+ * SRCU read-side critical sections, then loop waiting 1/HZ
+ * seconds per iteration. The 10-microsecond value has done
+ * very well in testing.
+ */
+
+ if (srcu_readers_active_idx(sp, idx))
+ udelay(SYNCHRONIZE_SRCU_READER_DELAY);
+ while (srcu_readers_active_idx(sp, idx))
+ schedule_timeout_interruptible(1);
+
+ sync_func(); /* 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);
+}
+
+/**
+ * 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 synchronize_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 synchronize_srcu(struct srcu_struct *sp)
+{
+ __synchronize_srcu(sp, synchronize_sched);
+}
+EXPORT_SYMBOL_GPL(synchronize_srcu);
+
+/**
+ * synchronize_srcu_expedited - Brute-force SRCU grace period
+ * @sp: srcu_struct with which to synchronize.
+ *
+ * Wait for an SRCU grace period to elapse, but use a "big hammer"
+ * approach to force the grace period to end quickly. This consumes
+ * significant time on all CPUs and is unfriendly to real-time workloads,
+ * so is thus not recommended for any sort of common-case code. In fact,
+ * if you are using synchronize_srcu_expedited() in a loop, please
+ * restructure your code to batch your updates, and then use a single
+ * synchronize_srcu() instead.
+ *
+ * Note that it is illegal to call this function while holding any lock
+ * that is acquired by a CPU-hotplug notifier. And yes, it is also illegal
+ * to call this function from a CPU-hotplug notifier. Failing to observe
+ * these restriction will result in deadlock. It is also illegal to call
+ * synchronize_srcu_expedited() from the corresponding SRCU read-side
+ * critical section; doing so will result in deadlock. However, it is
+ * perfectly legal to call synchronize_srcu_expedited() on one srcu_struct
+ * from some other srcu_struct's read-side critical section, as long as
+ * the resulting graph of srcu_structs is acyclic.
+ */
+void synchronize_srcu_expedited(struct srcu_struct *sp)
+{
+ __synchronize_srcu(sp, synchronize_sched_expedited);
+}
+EXPORT_SYMBOL_GPL(synchronize_srcu_expedited);
+
+/**
+ * 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 srcu_batches_completed(struct srcu_struct *sp)
+{
+ return sp->completed;
+}
+EXPORT_SYMBOL_GPL(srcu_batches_completed);