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srcu: Merge ->srcu_state into ->srcu_gp_seq

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Updating ->srcu_state and ->srcu_gp_seq will lead to extremely complex
race conditions given multiple callback queues, so this commit takes
advantage of the two-bit state now available in rcu_seq counters to
store the state in the bottom two bits of ->srcu_gp_seq.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney 2017-03-22 15:26:18 -07:00
parent f1ec57a462
commit 80a7956fe3
3 changed files with 46 additions and 24 deletions
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5
include/linux/srcu.h
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@ -43,8 +43,7 @@ struct srcu_struct {
unsigned long completed;
unsigned long srcu_gp_seq;
struct srcu_array __percpu *per_cpu_ref;
spinlock_t queue_lock; /* protect ->srcu_cblist, ->srcu_state */
int srcu_state;
spinlock_t queue_lock; /* protect ->srcu_cblist */
struct rcu_segcblist srcu_cblist;
struct delayed_work work;
#ifdef CONFIG_DEBUG_LOCK_ALLOC
@ -56,7 +55,6 @@ struct srcu_struct {
#define SRCU_STATE_IDLE 0
#define SRCU_STATE_SCAN1 1
#define SRCU_STATE_SCAN2 2
#define SRCU_STATE_DONE 3
#ifdef CONFIG_DEBUG_LOCK_ALLOC
@ -85,7 +83,6 @@ void process_srcu(struct work_struct *work);
.completed = -300, \
.per_cpu_ref = &name##_srcu_array, \
.queue_lock = __SPIN_LOCK_UNLOCKED(name.queue_lock), \
.srcu_state = SRCU_STATE_IDLE, \
.srcu_cblist = RCU_SEGCBLIST_INITIALIZER(name.srcu_cblist),\
.work = __DELAYED_WORK_INITIALIZER(name.work, process_srcu, 0),\
__SRCU_DEP_MAP_INIT(name) \