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-rw-r--r--kernel/rcutree.h31
1 files changed, 23 insertions, 8 deletions
diff --git a/kernel/rcutree.h b/kernel/rcutree.h
index 9aa8c8a160d8..a48d11f37b4c 100644
--- a/kernel/rcutree.h
+++ b/kernel/rcutree.h
@@ -79,15 +79,21 @@ struct rcu_dynticks {
* Definition for node within the RCU grace-period-detection hierarchy.
*/
struct rcu_node {
- spinlock_t lock;
+ spinlock_t lock; /* Root rcu_node's lock protects some */
+ /* rcu_state fields as well as following. */
long gpnum; /* Current grace period for this node. */
/* This will either be equal to or one */
/* behind the root rcu_node's gpnum. */
unsigned long qsmask; /* CPUs or groups that need to switch in */
/* order for current grace period to proceed.*/
+ /* In leaf rcu_node, each bit corresponds to */
+ /* an rcu_data structure, otherwise, each */
+ /* bit corresponds to a child rcu_node */
+ /* structure. */
unsigned long qsmaskinit;
/* Per-GP initialization for qsmask. */
unsigned long grpmask; /* Mask to apply to parent qsmask. */
+ /* Only one bit will be set in this mask. */
int grplo; /* lowest-numbered CPU or group here. */
int grphi; /* highest-numbered CPU or group here. */
u8 grpnum; /* CPU/group number for next level up. */
@@ -95,6 +101,9 @@ struct rcu_node {
struct rcu_node *parent;
struct list_head blocked_tasks[2];
/* Tasks blocked in RCU read-side critsect. */
+ /* Grace period number (->gpnum) x blocked */
+ /* by tasks on the (x & 0x1) element of the */
+ /* blocked_tasks[] array. */
} ____cacheline_internodealigned_in_smp;
/* Index values for nxttail array in struct rcu_data. */
@@ -126,19 +135,22 @@ struct rcu_data {
* Any of the partitions might be empty, in which case the
* pointer to that partition will be equal to the pointer for
* the following partition. When the list is empty, all of
- * the nxttail elements point to nxtlist, which is NULL.
+ * the nxttail elements point to the ->nxtlist pointer itself,
+ * which in that case is NULL.
*
- * [*nxttail[RCU_NEXT_READY_TAIL], NULL = *nxttail[RCU_NEXT_TAIL]):
- * Entries that might have arrived after current GP ended
- * [*nxttail[RCU_WAIT_TAIL], *nxttail[RCU_NEXT_READY_TAIL]):
- * Entries known to have arrived before current GP ended
- * [*nxttail[RCU_DONE_TAIL], *nxttail[RCU_WAIT_TAIL]):
- * Entries that batch # <= ->completed - 1: waiting for current GP
* [nxtlist, *nxttail[RCU_DONE_TAIL]):
* Entries that batch # <= ->completed
* The grace period for these entries has completed, and
* the other grace-period-completed entries may be moved
* here temporarily in rcu_process_callbacks().
+ * [*nxttail[RCU_DONE_TAIL], *nxttail[RCU_WAIT_TAIL]):
+ * Entries that batch # <= ->completed - 1: waiting for current GP
+ * [*nxttail[RCU_WAIT_TAIL], *nxttail[RCU_NEXT_READY_TAIL]):
+ * Entries known to have arrived before current GP ended
+ * [*nxttail[RCU_NEXT_READY_TAIL], *nxttail[RCU_NEXT_TAIL]):
+ * Entries that might have arrived after current GP ended
+ * Note that the value of *nxttail[RCU_NEXT_TAIL] will
+ * always be NULL, as this is the end of the list.
*/
struct rcu_head *nxtlist;
struct rcu_head **nxttail[RCU_NEXT_SIZE];
@@ -216,6 +228,9 @@ struct rcu_state {
/* Force QS state. */
long gpnum; /* Current gp number. */
long completed; /* # of last completed gp. */
+
+ /* End of fields guarded by root rcu_node's lock. */
+
spinlock_t onofflock; /* exclude on/offline and */
/* starting new GP. */
spinlock_t fqslock; /* Only one task forcing */