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rcu: Add expedited grace-period support for preemptible RCU

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Implement an synchronize_rcu_expedited() for preemptible RCU
that actually is expedited.  This uses
synchronize_sched_expedited() to force all threads currently
running in a preemptible-RCU read-side critical section onto the
appropriate ->blocked_tasks[] list, then takes a snapshot of all
of these lists and waits for them to drain.

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: <1259784616158-git-send-email->
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Paul E. McKenney
2009-12-02 12:10:15 -08:00
committed by Ingo Molnar
parent cf244dc01b
commit d9a3da0699
5 changed files with 260 additions and 27 deletions
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35
kernel/rcutree.h
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@@ -104,8 +104,12 @@ struct rcu_node {
/* an rcu_data structure, otherwise, each */
/* bit corresponds to a child rcu_node */
/* structure. */
unsigned long expmask; /* Groups that have ->blocked_tasks[] */
/* elements that need to drain to allow the */
/* current expedited grace period to */
/* complete (only for TREE_PREEMPT_RCU). */
unsigned long qsmaskinit;
/* Per-GP initialization for qsmask. */
/* Per-GP initial value for qsmask & expmask. */
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. */
@@ -113,7 +117,7 @@ struct rcu_node {
u8 grpnum; /* CPU/group number for next level up. */
u8 level; /* root is at level 0. */
struct rcu_node *parent;
struct list_head blocked_tasks[2];
struct list_head blocked_tasks[4];
/* Tasks blocked in RCU read-side critsect. */
/* Grace period number (->gpnum) x blocked */
/* by tasks on the (x & 0x1) element of the */
@@ -128,6 +132,21 @@ struct rcu_node {
for ((rnp) = &(rsp)->node[0]; \
(rnp) < &(rsp)->node[NUM_RCU_NODES]; (rnp)++)
/*
* Do a breadth-first scan of the non-leaf rcu_node structures for the
* specified rcu_state structure. Note that if there is a singleton
* rcu_node tree with but one rcu_node structure, this loop is a no-op.
*/
#define rcu_for_each_nonleaf_node_breadth_first(rsp, rnp) \
for ((rnp) = &(rsp)->node[0]; \
(rnp) < (rsp)->level[NUM_RCU_LVLS - 1]; (rnp)++)
/*
* Scan the leaves of the rcu_node hierarchy for the specified rcu_state
* structure. Note that if there is a singleton rcu_node tree with but
* one rcu_node structure, this loop -will- visit the rcu_node structure.
* It is still a leaf node, even if it is also the root node.
*/
#define rcu_for_each_leaf_node(rsp, rnp) \
for ((rnp) = (rsp)->level[NUM_RCU_LVLS - 1]; \
(rnp) < &(rsp)->node[NUM_RCU_NODES]; (rnp)++)
@@ -261,7 +280,7 @@ struct rcu_state {
long gpnum; /* Current gp number. */
long completed; /* # of last completed gp. */
/* End of fields guarded by root rcu_node's lock. */
/* End of fields guarded by root rcu_node's lock. */
spinlock_t onofflock; /* exclude on/offline and */
/* starting new GP. Also */
@@ -293,6 +312,13 @@ struct rcu_state {
#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
};
/* Return values for rcu_preempt_offline_tasks(). */
#define RCU_OFL_TASKS_NORM_GP 0x1 /* Tasks blocking normal */
/* GP were moved to root. */
#define RCU_OFL_TASKS_EXP_GP 0x2 /* Tasks blocking expedited */
/* GP were moved to root. */
#ifdef RCU_TREE_NONCORE
/*
@@ -333,6 +359,9 @@ static void rcu_preempt_offline_cpu(int cpu);
static void rcu_preempt_check_callbacks(int cpu);
static void rcu_preempt_process_callbacks(void);
void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu));
#if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_TREE_PREEMPT_RCU)
static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp);
#endif /* #if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_TREE_PREEMPT_RCU) */
static int rcu_preempt_pending(int cpu);
static int rcu_preempt_needs_cpu(int cpu);
static void __cpuinit rcu_preempt_init_percpu_data(int cpu);