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Commit dd7c4d89 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcu: performance fixes to TINY_PREEMPT_RCU callback checking 



This commit tightens up checks in rcu_preempt_check_callbacks() to avoid
unnecessary special handling at rcu_read_unlock() time.

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent 2c96c775

kernel/rcutiny_plugin.h

+8 −4
Original line number Diff line number Diff line
@@ -72,7 +72,7 @@ static void rcu_report_exp_done(void); 
/*

 * Return true if the CPU has not yet responded to the current grace period.

 */

static int rcu_cpu_cur_gp(void)

static int rcu_cpu_blocking_cur_gp(void)

{

	return rcu_preempt_ctrlblk.gpcpu != rcu_preempt_ctrlblk.gpnum;

}
@@ -229,7 +229,7 @@ void rcu_preempt_note_context_switch(void) 
		 * cannot end.

		 */

		list_add(&t->rcu_node_entry, &rcu_preempt_ctrlblk.blkd_tasks);

		if (rcu_cpu_cur_gp())

		if (rcu_cpu_blocking_cur_gp())

			rcu_preempt_ctrlblk.gp_tasks = &t->rcu_node_entry;

	}
@@ -368,12 +368,16 @@ static void rcu_preempt_check_callbacks(void) 
{

	struct task_struct *t = current;



	if (!rcu_preempt_running_reader() && rcu_preempt_gp_in_progress())

	if (rcu_preempt_gp_in_progress() &&

	    (!rcu_preempt_running_reader() ||

	     !rcu_cpu_blocking_cur_gp()))

		rcu_preempt_cpu_qs();

	if (&rcu_preempt_ctrlblk.rcb.rcucblist !=

	    rcu_preempt_ctrlblk.rcb.donetail)

		raise_softirq(RCU_SOFTIRQ);

	if (rcu_preempt_gp_in_progress() && rcu_preempt_running_reader())

	if (rcu_preempt_gp_in_progress() &&

	    rcu_cpu_blocking_cur_gp() &&

	    rcu_preempt_running_reader())

		t->rcu_read_unlock_special |= RCU_READ_UNLOCK_NEED_QS;

}