Commit-ID: 71da81324c83ef65bb196c7f874ac1c6996d8287
Gitweb: http://git.kernel.org/tip/71da81324c83ef65bb196c7f874ac1c6996d8287
Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
AuthorDate: Fri, 26 Feb 2010 16:38:58 -0800
Committer: Ingo Molnar <mingo@xxxxxxx>
CommitDate: Sat, 27 Feb 2010 09:53:53 +0100
rcu: Fix accelerated GPs for last non-dynticked CPU
This patch disables irqs across the call to rcu_needs_cpu(). It
also enforces a hold-off period so that the idle loop doesn't
softirq itself to death when there are lots of RCU callbacks in
flight on the last non-dynticked CPU.
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: laijs@xxxxxxxxxxxxxx
Cc: dipankar@xxxxxxxxxx
Cc: mathieu.desnoyers@xxxxxxxxxx
Cc: josh@xxxxxxxxxxxxxxxx
Cc: dvhltc@xxxxxxxxxx
Cc: niv@xxxxxxxxxx
Cc: peterz@xxxxxxxxxxxxx
Cc: rostedt@xxxxxxxxxxx
Cc: Valdis.Kletnieks@xxxxxx
Cc: dhowells@xxxxxxxxxx
LKML-Reference: <1267231138-27856-3-git-send-email-paulmck@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
---
kernel/rcutree_plugin.h | 10 +++++++++-
1 files changed, 9 insertions(+), 1 deletions(-)
diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index ed241fc..464ad2c 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -986,6 +986,7 @@ static void rcu_needs_cpu_flush(void)
#define RCU_NEEDS_CPU_FLUSHES 5
static DEFINE_PER_CPU(int, rcu_dyntick_drain);
+static DEFINE_PER_CPU(unsigned long, rcu_dyntick_holdoff);
/*
* Check to see if any future RCU-related work will need to be done
@@ -1013,6 +1014,7 @@ int rcu_needs_cpu(int cpu)
for_each_cpu_not(thatcpu, nohz_cpu_mask)
if (thatcpu != cpu) {
per_cpu(rcu_dyntick_drain, cpu) = 0;
+ per_cpu(rcu_dyntick_holdoff, cpu) = jiffies - 1;
return rcu_needs_cpu_quick_check(cpu);
}
@@ -1022,6 +1024,7 @@ int rcu_needs_cpu(int cpu)
per_cpu(rcu_dyntick_drain, cpu) = RCU_NEEDS_CPU_FLUSHES;
} else if (--per_cpu(rcu_dyntick_drain, cpu) <= 0) {
/* We have hit the limit, so time to give up. */
+ per_cpu(rcu_dyntick_holdoff, cpu) = jiffies;
return rcu_needs_cpu_quick_check(cpu);
}
@@ -1038,8 +1041,10 @@ int rcu_needs_cpu(int cpu)
}
/* If RCU callbacks are still pending, RCU still needs this CPU. */
- if (c)
+ if (c) {
raise_softirq(RCU_SOFTIRQ);
+ per_cpu(rcu_dyntick_holdoff, cpu) = jiffies;
+ }
return c;
}
@@ -1050,10 +1055,13 @@ int rcu_needs_cpu(int cpu)
static void rcu_needs_cpu_flush(void)
{
int cpu = smp_processor_id();
+ unsigned long flags;
if (per_cpu(rcu_dyntick_drain, cpu) <= 0)
return;
+ local_irq_save(flags);
(void)rcu_needs_cpu(cpu);
+ local_irq_restore(flags);
}
#endif /* #else #if !defined(CONFIG_RCU_FAST_NO_HZ) */
--
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