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authorLai Jiangshan <laijs@cn.fujitsu.com>2012-02-27 09:29:09 -0800
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2012-04-30 10:48:22 -0700
commitb52ce066c55a6a53cf1f8d71308d74f908e31b99 (patch)
treee814e4e175f2bd8e1c0795247f413d711c7350df /include/linux
parent18108ebfebe9e871d0a9af830baf8f5df69eb5fc (diff)
rcu: Implement a variant of Peter's SRCU algorithm
This commit implements a variant of Peter's algorithm, which may be found at https://lkml.org/lkml/2012/2/1/119. o Make the checking lock-free to enable parallel checking. Parallel checking is required when (1) the original checking task is preempted for a long time, (2) sychronize_srcu_expedited() starts during an ongoing SRCU grace period, or (3) we wish to avoid acquiring a lock. o Since the checking is lock-free, we avoid a mutex in state machine for call_srcu(). o Remove the SRCU_REF_MASK and remove the coupling with the flipping. This might allow us to remove the preempt_disable() in future versions, though such removal will need great care because it rescinds the one-old-reader-per-CPU guarantee. o Remove a smp_mb(), simplify the comments and make the smp_mb() pairs more intuitive. Inspired-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'include/linux')
-rw-r--r--include/linux/srcu.h7
1 files changed, 1 insertions, 6 deletions
diff --git a/include/linux/srcu.h b/include/linux/srcu.h
index 5b49d41868c..15354db3e86 100644
--- a/include/linux/srcu.h
+++ b/include/linux/srcu.h
@@ -32,18 +32,13 @@
struct srcu_struct_array {
unsigned long c[2];
+ unsigned long seq[2];
};
-/* Bit definitions for field ->c above and ->snap below. */
-#define SRCU_USAGE_BITS 1
-#define SRCU_REF_MASK (ULONG_MAX >> SRCU_USAGE_BITS)
-#define SRCU_USAGE_COUNT (SRCU_REF_MASK + 1)
-
struct srcu_struct {
unsigned completed;
struct srcu_struct_array __percpu *per_cpu_ref;
struct mutex mutex;
- unsigned long snap[NR_CPUS];
#ifdef CONFIG_DEBUG_LOCK_ALLOC
struct lockdep_map dep_map;
#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */