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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2009-09-13 09:15:10 -0700
committerIngo Molnar <mingo@elte.hu>2009-09-18 00:06:33 +0200
commitc3422bea5f09b0e85704f51f2b01271630b8940b (patch)
treefc4a18241b0f7f5d71211f6787428197769cb9f5 /kernel/rcutree.c
parentb0e165c035b13e1074fa0b555318bd9cb7102558 (diff)
rcu: Simplify rcu_read_unlock_special() quiescent-state accounting
The earlier approach required two scheduling-clock ticks to note an preemptable-RCU quiescent state in the situation in which the scheduling-clock interrupt is unlucky enough to always interrupt an RCU read-side critical section. With this change, the quiescent state is instead noted by the outermost rcu_read_unlock() immediately following the first scheduling-clock tick, or, alternatively, by the first subsequent context switch. Therefore, this change also speeds up grace periods. Suggested-by: Josh Triplett <josh@joshtriplett.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: akpm@linux-foundation.org Cc: mathieu.desnoyers@polymtl.ca Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org Cc: Valdis.Kletnieks@vt.edu LKML-Reference: <12528585111945-git-send-email-> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/rcutree.c')
-rw-r--r--kernel/rcutree.c15
1 files changed, 6 insertions, 9 deletions
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index e9a4ae94647..6c99553e9f1 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -107,27 +107,23 @@ static void __cpuinit rcu_init_percpu_data(int cpu, struct rcu_state *rsp,
*/
void rcu_sched_qs(int cpu)
{
- unsigned long flags;
struct rcu_data *rdp;
- local_irq_save(flags);
rdp = &per_cpu(rcu_sched_data, cpu);
- rdp->passed_quiesc = 1;
rdp->passed_quiesc_completed = rdp->completed;
- rcu_preempt_qs(cpu);
- local_irq_restore(flags);
+ barrier();
+ rdp->passed_quiesc = 1;
+ rcu_preempt_note_context_switch(cpu);
}
void rcu_bh_qs(int cpu)
{
- unsigned long flags;
struct rcu_data *rdp;
- local_irq_save(flags);
rdp = &per_cpu(rcu_bh_data, cpu);
- rdp->passed_quiesc = 1;
rdp->passed_quiesc_completed = rdp->completed;
- local_irq_restore(flags);
+ barrier();
+ rdp->passed_quiesc = 1;
}
#ifdef CONFIG_NO_HZ
@@ -615,6 +611,7 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
/* Advance to a new grace period and initialize state. */
rsp->gpnum++;
+ WARN_ON_ONCE(rsp->signaled == RCU_GP_INIT);
rsp->signaled = RCU_GP_INIT; /* Hold off force_quiescent_state. */
rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS;
record_gp_stall_check_time(rsp);