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Merge branches 'bigrtm.2012.07.04a', 'doctorture.2012.07.02a', 'fixes.2012.07.06a' and 'fnh.2012.07.02a' into HEAD

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bigrtm: First steps towards getting RCU out of the way of
	tens-of-microseconds real-time response on systems compiled
	with NR_CPUS=4096.  Also cleanups for and increased concurrency
	of rcu_barrier() family of primitives.
doctorture: rcutorture and documentation improvements.
fixes:  Miscellaneous fixes.
fnh: RCU_FAST_NO_HZ fixes and improvements.
This commit is contained in:
Paul E. McKenney
2012-07-06 05:59:20 -07:00
parent ff015030c9 72472a02a9 cfca927972 9d2ad24306
commit 02a0677b0b
15 changed files with 252 additions and 258 deletions
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49
kernel/rcutiny_plugin.h
View File

@@ -132,7 +132,6 @@ static struct rcu_preempt_ctrlblk rcu_preempt_ctrlblk = {
RCU_TRACE(.rcb.name = "rcu_preempt")
};
static void rcu_read_unlock_special(struct task_struct *t);
static int rcu_preempted_readers_exp(void);
static void rcu_report_exp_done(void);
@@ -526,24 +525,12 @@ void rcu_preempt_note_context_switch(void)
local_irq_restore(flags);
}
/*
* Tiny-preemptible RCU implementation for rcu_read_lock().
* Just increment ->rcu_read_lock_nesting, shared state will be updated
* if we block.
*/
void __rcu_read_lock(void)
{
current->rcu_read_lock_nesting++;
barrier(); /* needed if we ever invoke rcu_read_lock in rcutiny.c */
}
EXPORT_SYMBOL_GPL(__rcu_read_lock);
/*
* Handle special cases during rcu_read_unlock(), such as needing to
* notify RCU core processing or task having blocked during the RCU
* read-side critical section.
*/
static noinline void rcu_read_unlock_special(struct task_struct *t)
void rcu_read_unlock_special(struct task_struct *t)
{
int empty;
int empty_exp;
@@ -626,38 +613,6 @@ static noinline void rcu_read_unlock_special(struct task_struct *t)
local_irq_restore(flags);
}
/*
* Tiny-preemptible RCU implementation for rcu_read_unlock().
* Decrement ->rcu_read_lock_nesting. If the result is zero (outermost
* rcu_read_unlock()) and ->rcu_read_unlock_special is non-zero, then
* invoke rcu_read_unlock_special() to clean up after a context switch
* in an RCU read-side critical section and other special cases.
*/
void __rcu_read_unlock(void)
{
struct task_struct *t = current;
barrier(); /* needed if we ever invoke rcu_read_unlock in rcutiny.c */
if (t->rcu_read_lock_nesting != 1)
--t->rcu_read_lock_nesting;
else {
t->rcu_read_lock_nesting = INT_MIN;
barrier(); /* assign before ->rcu_read_unlock_special load */
if (unlikely(ACCESS_ONCE(t->rcu_read_unlock_special)))
rcu_read_unlock_special(t);
barrier(); /* ->rcu_read_unlock_special load before assign */
t->rcu_read_lock_nesting = 0;
}
#ifdef CONFIG_PROVE_LOCKING
{
int rrln = ACCESS_ONCE(t->rcu_read_lock_nesting);
WARN_ON_ONCE(rrln < 0 && rrln > INT_MIN / 2);
}
#endif /* #ifdef CONFIG_PROVE_LOCKING */
}
EXPORT_SYMBOL_GPL(__rcu_read_unlock);
/*
* Check for a quiescent state from the current CPU. When a task blocks,
* the task is recorded in the rcu_preempt_ctrlblk structure, which is
@@ -846,8 +801,6 @@ EXPORT_SYMBOL_GPL(synchronize_rcu_expedited);
*/
int rcu_preempt_needs_cpu(void)
{
if (!rcu_preempt_running_reader())
rcu_preempt_cpu_qs();
return rcu_preempt_ctrlblk.rcb.rcucblist != NULL;
}