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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2010-02-22 17:04:59 -0800
committerIngo Molnar <mingo@elte.hu>2010-02-25 10:34:55 +0100
commit8bd93a2c5d4cab2ae17d06350daa7dbf546a4634 (patch)
tree3facbdbfbcc1b169fad20f456b0a2521adadfb25 /include
parent998f2ac3fea93bfa8b55c279fff68f7c5b9ab93d (diff)
rcu: Accelerate grace period if last non-dynticked CPU
Currently, rcu_needs_cpu() simply checks whether the current CPU has an outstanding RCU callback, which means that the last CPU to go into dyntick-idle mode might wait a few ticks for the relevant grace periods to complete. However, if all the other CPUs are in dyntick-idle mode, and if this CPU is in a quiescent state (which it is for RCU-bh and RCU-sched any time that we are considering going into dyntick-idle mode), then the grace period is instantly complete. This patch therefore repeatedly invokes the RCU grace-period machinery in order to force any needed grace periods to complete quickly. It does so a limited number of times in order to prevent starvation by an RCU callback function that might pass itself to call_rcu(). However, if any CPU other than the current one is not in dyntick-idle mode, fall back to simply checking (with fix to bug noted by Lai Jiangshan). Also, take advantage of last grace-period forcing, the opportunity to do so noted by Steve Rostedt. And apply simplified #ifdef condition suggested by Frederic Weisbecker. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: mathieu.desnoyers@polymtl.ca Cc: josh@joshtriplett.org Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org Cc: Valdis.Kletnieks@vt.edu Cc: dhowells@redhat.com LKML-Reference: <1266887105-1528-15-git-send-email-paulmck@linux.vnet.ibm.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'include')
-rw-r--r--include/linux/cpumask.h14
1 files changed, 14 insertions, 0 deletions
diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index d77b54733c5..dbcee7647d9 100644
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -143,6 +143,8 @@ static inline unsigned int cpumask_any_but(const struct cpumask *mask,
#define for_each_cpu(cpu, mask) \
for ((cpu) = 0; (cpu) < 1; (cpu)++, (void)mask)
+#define for_each_cpu_not(cpu, mask) \
+ for ((cpu) = 0; (cpu) < 1; (cpu)++, (void)mask)
#define for_each_cpu_and(cpu, mask, and) \
for ((cpu) = 0; (cpu) < 1; (cpu)++, (void)mask, (void)and)
#else
@@ -203,6 +205,18 @@ int cpumask_any_but(const struct cpumask *mask, unsigned int cpu);
(cpu) < nr_cpu_ids;)
/**
+ * for_each_cpu_not - iterate over every cpu in a complemented mask
+ * @cpu: the (optionally unsigned) integer iterator
+ * @mask: the cpumask pointer
+ *
+ * After the loop, cpu is >= nr_cpu_ids.
+ */
+#define for_each_cpu_not(cpu, mask) \
+ for ((cpu) = -1; \
+ (cpu) = cpumask_next_zero((cpu), (mask)), \
+ (cpu) < nr_cpu_ids;)
+
+/**
* for_each_cpu_and - iterate over every cpu in both masks
* @cpu: the (optionally unsigned) integer iterator
* @mask: the first cpumask pointer