| From | Frederic Weisbecker <> | Subject | [PATCH 22/32] rcu: Restart tick if we enqueue a callback in a nohz/cpuset CPU | Date | Mon, 15 Aug 2011 17:52:19 +0200 |
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If we enqueue an rcu callback, we need the CPU tick to stay alive until we take care of those by completing the appropriate grace period.
Thus, when we call_rcu(), send a self IPI that checks rcu_needs_cpu() so that we restore a periodic tick behaviour that can take care of everything.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Anton Blanchard <anton@au1.ibm.com> Cc: Avi Kivity <avi@redhat.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Lai Jiangshan <laijs@cn.fujitsu.com> Cc: Paul E . McKenney <paulmck@linux.vnet.ibm.com> Cc: Paul Menage <menage@google.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Stephen Hemminger <shemminger@vyatta.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Tim Pepper <lnxninja@linux.vnet.ibm.com> --- kernel/rcutree.c | 8 ++++++++ 1 files changed, 8 insertions(+), 0 deletions(-)
diff --git a/kernel/rcutree.c b/kernel/rcutree.c index d496c70..b5643ce2 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -51,6 +51,7 @@ #include <linux/kthread.h> #include <linux/prefetch.h> #include <linux/cpuset.h> +#include <linux/tick.h> #include "rcutree.h" @@ -1546,6 +1547,13 @@ __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu), rdp->nxttail[RCU_NEXT_TAIL] = &head->next; rdp->qlen++; + /* Restart the timer if needed to handle the callbacks */ + if (tick_nohz_adaptive_mode()) { + /* Make updates on nxtlist visible to self IPI */ + barrier(); + smp_cpuset_update_nohz(smp_processor_id()); + } + /* If interrupts were disabled, don't dive into RCU core. */ if (irqs_disabled_flags(flags)) { local_irq_restore(flags); -- 1.7.5.4
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