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Subject[GIT PULL] core kernel fixes
Linus,

Please pull the latest core-fixes-for-linus git tree from:

git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip.git core-fixes-for-linus

Thanks,

Ingo

------------------>
Paul E. McKenney (2):
rcu: demote SRCU_SYNCHRONIZE_DELAY from kernel-parameter status
rcu: avoid pointless blocked-task warnings
Steven Rostedt (1):
rtmutex: Fix comment about why new_owner can be NULL in wake_futex_pi()


init/Kconfig | 15 ---------------
kernel/futex.c | 7 +++----
kernel/rcutiny.c | 3 ++-
kernel/srcu.c | 15 +++++++++++++--
4 files changed, 18 insertions(+), 22 deletions(-)
diff --git a/init/Kconfig b/init/Kconfig
index 8dfd094..bd1ea92 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -497,21 +497,6 @@ config RCU_BOOST_DELAY

Accept the default if unsure.

-config SRCU_SYNCHRONIZE_DELAY
- int "Microseconds to delay before waiting for readers"
- range 0 20
- default 10
- help
- This option controls how long SRCU delays before entering its
- loop waiting on SRCU readers. The purpose of this loop is
- to avoid the unconditional context-switch penalty that would
- otherwise be incurred if there was an active SRCU reader,
- in a manner similar to adaptive locking schemes. This should
- be set to be a bit longer than the common-case SRCU read-side
- critical-section overhead.
-
- Accept the default if unsure.
-
endmenu # "RCU Subsystem"

config IKCONFIG
diff --git a/kernel/futex.c b/kernel/futex.c
index 3019b92..5696d38 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -791,10 +791,9 @@ static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this)
new_owner = rt_mutex_next_owner(&pi_state->pi_mutex);

/*
- * This happens when we have stolen the lock and the original
- * pending owner did not enqueue itself back on the rt_mutex.
- * Thats not a tragedy. We know that way, that a lock waiter
- * is on the fly. We make the futex_q waiter the pending owner.
+ * It is possible that the next waiter (the one that brought
+ * this owner to the kernel) timed out and is no longer
+ * waiting on the lock.
*/
if (!new_owner)
new_owner = this->task;
diff --git a/kernel/rcutiny.c b/kernel/rcutiny.c
index 0344937..0c343b9 100644
--- a/kernel/rcutiny.c
+++ b/kernel/rcutiny.c
@@ -189,7 +189,8 @@ static int rcu_kthread(void *arg)
unsigned long flags;

for (;;) {
- wait_event(rcu_kthread_wq, have_rcu_kthread_work != 0);
+ wait_event_interruptible(rcu_kthread_wq,
+ have_rcu_kthread_work != 0);
morework = rcu_boost();
local_irq_save(flags);
work = have_rcu_kthread_work;
diff --git a/kernel/srcu.c b/kernel/srcu.c
index 98d8c1e..73ce23f 100644
--- a/kernel/srcu.c
+++ b/kernel/srcu.c
@@ -156,6 +156,16 @@ void __srcu_read_unlock(struct srcu_struct *sp, int idx)
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))
@@ -207,11 +217,12 @@ static void __synchronize_srcu(struct srcu_struct *sp, void (*sync_func)(void))
* 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.
+ * seconds per iteration. The 10-microsecond value has done
+ * very well in testing.
*/

if (srcu_readers_active_idx(sp, idx))
- udelay(CONFIG_SRCU_SYNCHRONIZE_DELAY);
+ udelay(SYNCHRONIZE_SRCU_READER_DELAY);
while (srcu_readers_active_idx(sp, idx))
schedule_timeout_interruptible(1);


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