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authorPaul E. McKenney <paul.mckenney@linaro.org>2012-01-23 17:05:46 -0800
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2012-02-21 09:06:04 -0800
commit3d3b7db0a22085cfc05c3318b9874f7fb8266d18 (patch)
tree7f6a080ca64f8a07dd058c2771b983c602fd1a65 /kernel/rcutree_plugin.h
parentc0d6d01bffdce19fa19baad6cb8cc3eed7bfd6f5 (diff)
downloadop-kernel-dev-3d3b7db0a22085cfc05c3318b9874f7fb8266d18.zip
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rcu: Move synchronize_sched_expedited() to rcutree.c
Now that TREE_RCU and TREE_PREEMPT_RCU no longer do anything different for the single-CPU case, there is no need for multiple definitions of synchronize_sched_expedited(). It is no longer in any sense a plug-in, so move it from kernel/rcutree_plugin.h to kernel/rcutree.c. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'kernel/rcutree_plugin.h')
-rw-r--r--kernel/rcutree_plugin.h116
1 files changed, 0 insertions, 116 deletions
diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index cecea84..98ce17c 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -25,7 +25,6 @@
*/
#include <linux/delay.h>
-#include <linux/stop_machine.h>
#define RCU_KTHREAD_PRIO 1
@@ -1888,121 +1887,6 @@ static void __cpuinit rcu_prepare_kthreads(int cpu)
#endif /* #else #ifdef CONFIG_RCU_BOOST */
-static atomic_t sync_sched_expedited_started = ATOMIC_INIT(0);
-static atomic_t sync_sched_expedited_done = ATOMIC_INIT(0);
-
-static int synchronize_sched_expedited_cpu_stop(void *data)
-{
- /*
- * There must be a full memory barrier on each affected CPU
- * between the time that try_stop_cpus() is called and the
- * time that it returns.
- *
- * In the current initial implementation of cpu_stop, the
- * above condition is already met when the control reaches
- * this point and the following smp_mb() is not strictly
- * necessary. Do smp_mb() anyway for documentation and
- * robustness against future implementation changes.
- */
- smp_mb(); /* See above comment block. */
- return 0;
-}
-
-/*
- * Wait for an rcu-sched grace period to elapse, but use "big hammer"
- * approach to force grace period to end quickly. This consumes
- * significant time on all CPUs, and is thus not recommended for
- * any sort of common-case code.
- *
- * Note that it is illegal to call this function while holding any
- * lock that is acquired by a CPU-hotplug notifier. Failing to
- * observe this restriction will result in deadlock.
- *
- * This implementation can be thought of as an application of ticket
- * locking to RCU, with sync_sched_expedited_started and
- * sync_sched_expedited_done taking on the roles of the halves
- * of the ticket-lock word. Each task atomically increments
- * sync_sched_expedited_started upon entry, snapshotting the old value,
- * then attempts to stop all the CPUs. If this succeeds, then each
- * CPU will have executed a context switch, resulting in an RCU-sched
- * grace period. We are then done, so we use atomic_cmpxchg() to
- * update sync_sched_expedited_done to match our snapshot -- but
- * only if someone else has not already advanced past our snapshot.
- *
- * On the other hand, if try_stop_cpus() fails, we check the value
- * of sync_sched_expedited_done. If it has advanced past our
- * initial snapshot, then someone else must have forced a grace period
- * some time after we took our snapshot. In this case, our work is
- * done for us, and we can simply return. Otherwise, we try again,
- * but keep our initial snapshot for purposes of checking for someone
- * doing our work for us.
- *
- * If we fail too many times in a row, we fall back to synchronize_sched().
- */
-void synchronize_sched_expedited(void)
-{
- int firstsnap, s, snap, trycount = 0;
-
- /* Note that atomic_inc_return() implies full memory barrier. */
- firstsnap = snap = atomic_inc_return(&sync_sched_expedited_started);
- get_online_cpus();
- WARN_ON_ONCE(cpu_is_offline(smp_processor_id()));
-
- /*
- * Each pass through the following loop attempts to force a
- * context switch on each CPU.
- */
- while (try_stop_cpus(cpu_online_mask,
- synchronize_sched_expedited_cpu_stop,
- NULL) == -EAGAIN) {
- put_online_cpus();
-
- /* No joy, try again later. Or just synchronize_sched(). */
- if (trycount++ < 10)
- udelay(trycount * num_online_cpus());
- else {
- synchronize_sched();
- return;
- }
-
- /* Check to see if someone else did our work for us. */
- s = atomic_read(&sync_sched_expedited_done);
- if (UINT_CMP_GE((unsigned)s, (unsigned)firstsnap)) {
- smp_mb(); /* ensure test happens before caller kfree */
- return;
- }
-
- /*
- * Refetching sync_sched_expedited_started allows later
- * callers to piggyback on our grace period. We subtract
- * 1 to get the same token that the last incrementer got.
- * We retry after they started, so our grace period works
- * for them, and they started after our first try, so their
- * grace period works for us.
- */
- get_online_cpus();
- snap = atomic_read(&sync_sched_expedited_started);
- smp_mb(); /* ensure read is before try_stop_cpus(). */
- }
-
- /*
- * Everyone up to our most recent fetch is covered by our grace
- * period. Update the counter, but only if our work is still
- * relevant -- which it won't be if someone who started later
- * than we did beat us to the punch.
- */
- do {
- s = atomic_read(&sync_sched_expedited_done);
- if (UINT_CMP_GE((unsigned)s, (unsigned)snap)) {
- smp_mb(); /* ensure test happens before caller kfree */
- break;
- }
- } while (atomic_cmpxchg(&sync_sched_expedited_done, s, snap) != s);
-
- put_online_cpus();
-}
-EXPORT_SYMBOL_GPL(synchronize_sched_expedited);
-
#if !defined(CONFIG_RCU_FAST_NO_HZ)
/*
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