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https://github.com/followmsi/android_kernel_google_msm.git
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rcu: Add expedited grace-period support for preemptible RCU
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:
parent
cf244dc01b
commit
d9a3da0699
5 changed files with 260 additions and 27 deletions
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@ -327,6 +327,11 @@ rcu_torture_cb(struct rcu_head *p)
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cur_ops->deferred_free(rp);
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}
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static int rcu_no_completed(void)
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{
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return 0;
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}
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static void rcu_torture_deferred_free(struct rcu_torture *p)
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{
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call_rcu(&p->rtort_rcu, rcu_torture_cb);
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@ -388,6 +393,21 @@ static struct rcu_torture_ops rcu_sync_ops = {
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.name = "rcu_sync"
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};
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static struct rcu_torture_ops rcu_expedited_ops = {
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.init = rcu_sync_torture_init,
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.cleanup = NULL,
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.readlock = rcu_torture_read_lock,
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.read_delay = rcu_read_delay, /* just reuse rcu's version. */
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.readunlock = rcu_torture_read_unlock,
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.completed = rcu_no_completed,
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.deferred_free = rcu_sync_torture_deferred_free,
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.sync = synchronize_rcu_expedited,
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.cb_barrier = NULL,
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.stats = NULL,
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.irq_capable = 1,
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.name = "rcu_expedited"
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};
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/*
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* Definitions for rcu_bh torture testing.
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*/
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@ -581,11 +601,6 @@ static void sched_torture_read_unlock(int idx)
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preempt_enable();
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}
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static int sched_torture_completed(void)
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{
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return 0;
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}
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static void rcu_sched_torture_deferred_free(struct rcu_torture *p)
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{
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call_rcu_sched(&p->rtort_rcu, rcu_torture_cb);
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@ -602,7 +617,7 @@ static struct rcu_torture_ops sched_ops = {
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.readlock = sched_torture_read_lock,
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.read_delay = rcu_read_delay, /* just reuse rcu's version. */
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.readunlock = sched_torture_read_unlock,
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.completed = sched_torture_completed,
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.completed = rcu_no_completed,
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.deferred_free = rcu_sched_torture_deferred_free,
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.sync = sched_torture_synchronize,
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.cb_barrier = rcu_barrier_sched,
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@ -617,7 +632,7 @@ static struct rcu_torture_ops sched_sync_ops = {
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.readlock = sched_torture_read_lock,
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.read_delay = rcu_read_delay, /* just reuse rcu's version. */
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.readunlock = sched_torture_read_unlock,
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.completed = sched_torture_completed,
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.completed = rcu_no_completed,
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.deferred_free = rcu_sync_torture_deferred_free,
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.sync = sched_torture_synchronize,
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.cb_barrier = NULL,
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@ -631,7 +646,7 @@ static struct rcu_torture_ops sched_expedited_ops = {
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.readlock = sched_torture_read_lock,
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.read_delay = rcu_read_delay, /* just reuse rcu's version. */
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.readunlock = sched_torture_read_unlock,
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.completed = sched_torture_completed,
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.completed = rcu_no_completed,
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.deferred_free = rcu_sync_torture_deferred_free,
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.sync = synchronize_sched_expedited,
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.cb_barrier = NULL,
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@ -1116,7 +1131,8 @@ rcu_torture_init(void)
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int cpu;
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int firsterr = 0;
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static struct rcu_torture_ops *torture_ops[] =
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{ &rcu_ops, &rcu_sync_ops, &rcu_bh_ops, &rcu_bh_sync_ops,
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{ &rcu_ops, &rcu_sync_ops, &rcu_expedited_ops,
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&rcu_bh_ops, &rcu_bh_sync_ops,
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&srcu_ops, &srcu_expedited_ops,
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&sched_ops, &sched_sync_ops, &sched_expedited_ops, };
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@ -948,7 +948,7 @@ static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp)
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{
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unsigned long flags;
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unsigned long mask;
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int need_quiet = 0;
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int need_report = 0;
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struct rcu_data *rdp = rsp->rda[cpu];
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struct rcu_node *rnp;
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@ -967,7 +967,7 @@ static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp)
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break;
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}
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if (rnp == rdp->mynode)
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need_quiet = rcu_preempt_offline_tasks(rsp, rnp, rdp);
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need_report = rcu_preempt_offline_tasks(rsp, rnp, rdp);
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else
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spin_unlock(&rnp->lock); /* irqs remain disabled. */
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mask = rnp->grpmask;
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@ -982,10 +982,12 @@ static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp)
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*/
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spin_unlock(&rsp->onofflock); /* irqs remain disabled. */
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rnp = rdp->mynode;
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if (need_quiet)
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if (need_report & RCU_OFL_TASKS_NORM_GP)
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rcu_report_unblock_qs_rnp(rnp, flags);
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else
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spin_unlock_irqrestore(&rnp->lock, flags);
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if (need_report & RCU_OFL_TASKS_EXP_GP)
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rcu_report_exp_rnp(rsp, rnp);
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rcu_adopt_orphan_cbs(rsp);
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}
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@ -1843,6 +1845,8 @@ static void __init rcu_init_one(struct rcu_state *rsp)
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rnp->level = i;
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INIT_LIST_HEAD(&rnp->blocked_tasks[0]);
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INIT_LIST_HEAD(&rnp->blocked_tasks[1]);
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INIT_LIST_HEAD(&rnp->blocked_tasks[2]);
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INIT_LIST_HEAD(&rnp->blocked_tasks[3]);
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}
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}
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}
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@ -104,8 +104,12 @@ struct rcu_node {
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/* an rcu_data structure, otherwise, each */
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/* bit corresponds to a child rcu_node */
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/* structure. */
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unsigned long expmask; /* Groups that have ->blocked_tasks[] */
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/* elements that need to drain to allow the */
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/* current expedited grace period to */
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/* complete (only for TREE_PREEMPT_RCU). */
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unsigned long qsmaskinit;
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/* Per-GP initialization for qsmask. */
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/* Per-GP initial value for qsmask & expmask. */
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unsigned long grpmask; /* Mask to apply to parent qsmask. */
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/* Only one bit will be set in this mask. */
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int grplo; /* lowest-numbered CPU or group here. */
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@ -113,7 +117,7 @@ struct rcu_node {
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u8 grpnum; /* CPU/group number for next level up. */
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u8 level; /* root is at level 0. */
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struct rcu_node *parent;
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struct list_head blocked_tasks[2];
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struct list_head blocked_tasks[4];
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/* Tasks blocked in RCU read-side critsect. */
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/* Grace period number (->gpnum) x blocked */
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/* by tasks on the (x & 0x1) element of the */
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@ -128,6 +132,21 @@ struct rcu_node {
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for ((rnp) = &(rsp)->node[0]; \
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(rnp) < &(rsp)->node[NUM_RCU_NODES]; (rnp)++)
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/*
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* Do a breadth-first scan of the non-leaf rcu_node structures for the
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* specified rcu_state structure. Note that if there is a singleton
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* rcu_node tree with but one rcu_node structure, this loop is a no-op.
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*/
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#define rcu_for_each_nonleaf_node_breadth_first(rsp, rnp) \
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for ((rnp) = &(rsp)->node[0]; \
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(rnp) < (rsp)->level[NUM_RCU_LVLS - 1]; (rnp)++)
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/*
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* Scan the leaves of the rcu_node hierarchy for the specified rcu_state
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* structure. Note that if there is a singleton rcu_node tree with but
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* one rcu_node structure, this loop -will- visit the rcu_node structure.
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* It is still a leaf node, even if it is also the root node.
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*/
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#define rcu_for_each_leaf_node(rsp, rnp) \
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for ((rnp) = (rsp)->level[NUM_RCU_LVLS - 1]; \
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(rnp) < &(rsp)->node[NUM_RCU_NODES]; (rnp)++)
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@ -261,7 +280,7 @@ struct rcu_state {
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long gpnum; /* Current gp number. */
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long completed; /* # of last completed gp. */
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/* End of fields guarded by root rcu_node's lock. */
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/* End of fields guarded by root rcu_node's lock. */
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spinlock_t onofflock; /* exclude on/offline and */
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/* starting new GP. Also */
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@ -293,6 +312,13 @@ struct rcu_state {
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#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
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};
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/* Return values for rcu_preempt_offline_tasks(). */
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#define RCU_OFL_TASKS_NORM_GP 0x1 /* Tasks blocking normal */
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/* GP were moved to root. */
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#define RCU_OFL_TASKS_EXP_GP 0x2 /* Tasks blocking expedited */
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/* GP were moved to root. */
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#ifdef RCU_TREE_NONCORE
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/*
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@ -333,6 +359,9 @@ static void rcu_preempt_offline_cpu(int cpu);
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static void rcu_preempt_check_callbacks(int cpu);
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static void rcu_preempt_process_callbacks(void);
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void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu));
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#if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_TREE_PREEMPT_RCU)
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static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp);
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#endif /* #if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_TREE_PREEMPT_RCU) */
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static int rcu_preempt_pending(int cpu);
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static int rcu_preempt_needs_cpu(int cpu);
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static void __cpuinit rcu_preempt_init_percpu_data(int cpu);
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@ -24,12 +24,15 @@
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* Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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*/
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#include <linux/delay.h>
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#ifdef CONFIG_TREE_PREEMPT_RCU
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struct rcu_state rcu_preempt_state = RCU_STATE_INITIALIZER(rcu_preempt_state);
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DEFINE_PER_CPU(struct rcu_data, rcu_preempt_data);
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static int rcu_preempted_readers_exp(struct rcu_node *rnp);
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/*
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* Tell them what RCU they are running.
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*/
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*/
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static int rcu_preempted_readers(struct rcu_node *rnp)
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{
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return !list_empty(&rnp->blocked_tasks[rnp->gpnum & 0x1]);
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int phase = rnp->gpnum & 0x1;
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return !list_empty(&rnp->blocked_tasks[phase]) ||
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!list_empty(&rnp->blocked_tasks[phase + 2]);
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}
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/*
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@ -204,6 +210,7 @@ static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp, unsigned long flags)
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static void rcu_read_unlock_special(struct task_struct *t)
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{
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int empty;
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int empty_exp;
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unsigned long flags;
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struct rcu_node *rnp;
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int special;
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@ -247,6 +254,8 @@ static void rcu_read_unlock_special(struct task_struct *t)
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spin_unlock(&rnp->lock); /* irqs remain disabled. */
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}
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empty = !rcu_preempted_readers(rnp);
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empty_exp = !rcu_preempted_readers_exp(rnp);
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smp_mb(); /* ensure expedited fastpath sees end of RCU c-s. */
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list_del_init(&t->rcu_node_entry);
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t->rcu_blocked_node = NULL;
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@ -259,6 +268,13 @@ static void rcu_read_unlock_special(struct task_struct *t)
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spin_unlock_irqrestore(&rnp->lock, flags);
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else
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rcu_report_unblock_qs_rnp(rnp, flags);
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/*
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* If this was the last task on the expedited lists,
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* then we need to report up the rcu_node hierarchy.
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*/
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if (!empty_exp && !rcu_preempted_readers_exp(rnp))
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rcu_report_exp_rnp(&rcu_preempt_state, rnp);
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} else {
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local_irq_restore(flags);
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}
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@ -343,7 +359,7 @@ static int rcu_preempt_offline_tasks(struct rcu_state *rsp,
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int i;
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struct list_head *lp;
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struct list_head *lp_root;
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int retval;
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int retval = 0;
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struct rcu_node *rnp_root = rcu_get_root(rsp);
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struct task_struct *tp;
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@ -353,7 +369,9 @@ static int rcu_preempt_offline_tasks(struct rcu_state *rsp,
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}
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WARN_ON_ONCE(rnp != rdp->mynode &&
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(!list_empty(&rnp->blocked_tasks[0]) ||
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!list_empty(&rnp->blocked_tasks[1])));
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!list_empty(&rnp->blocked_tasks[1]) ||
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!list_empty(&rnp->blocked_tasks[2]) ||
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!list_empty(&rnp->blocked_tasks[3])));
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/*
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* Move tasks up to root rcu_node. Rely on the fact that the
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@ -361,8 +379,11 @@ static int rcu_preempt_offline_tasks(struct rcu_state *rsp,
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* rcu_nodes in terms of gp_num value. This fact allows us to
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* move the blocked_tasks[] array directly, element by element.
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*/
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retval = rcu_preempted_readers(rnp);
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for (i = 0; i < 2; i++) {
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if (rcu_preempted_readers(rnp))
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retval |= RCU_OFL_TASKS_NORM_GP;
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if (rcu_preempted_readers_exp(rnp))
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retval |= RCU_OFL_TASKS_EXP_GP;
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for (i = 0; i < 4; i++) {
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lp = &rnp->blocked_tasks[i];
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lp_root = &rnp_root->blocked_tasks[i];
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while (!list_empty(lp)) {
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@ -449,14 +470,159 @@ void synchronize_rcu(void)
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}
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EXPORT_SYMBOL_GPL(synchronize_rcu);
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static DECLARE_WAIT_QUEUE_HEAD(sync_rcu_preempt_exp_wq);
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static long sync_rcu_preempt_exp_count;
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static DEFINE_MUTEX(sync_rcu_preempt_exp_mutex);
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/*
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* Wait for an rcu-preempt grace period. We are supposed to expedite the
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* grace period, but this is the crude slow compatability hack, so just
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* invoke synchronize_rcu().
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* Return non-zero if there are any tasks in RCU read-side critical
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* sections blocking the current preemptible-RCU expedited grace period.
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* If there is no preemptible-RCU expedited grace period currently in
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* progress, returns zero unconditionally.
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*/
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static int rcu_preempted_readers_exp(struct rcu_node *rnp)
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{
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return !list_empty(&rnp->blocked_tasks[2]) ||
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!list_empty(&rnp->blocked_tasks[3]);
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}
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/*
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* return non-zero if there is no RCU expedited grace period in progress
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* for the specified rcu_node structure, in other words, if all CPUs and
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* tasks covered by the specified rcu_node structure have done their bit
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* for the current expedited grace period. Works only for preemptible
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* RCU -- other RCU implementation use other means.
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*
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* Caller must hold sync_rcu_preempt_exp_mutex.
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*/
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static int sync_rcu_preempt_exp_done(struct rcu_node *rnp)
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{
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return !rcu_preempted_readers_exp(rnp) &&
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ACCESS_ONCE(rnp->expmask) == 0;
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}
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/*
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* Report the exit from RCU read-side critical section for the last task
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* that queued itself during or before the current expedited preemptible-RCU
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* grace period. This event is reported either to the rcu_node structure on
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* which the task was queued or to one of that rcu_node structure's ancestors,
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* recursively up the tree. (Calm down, calm down, we do the recursion
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* iteratively!)
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*
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* Caller must hold sync_rcu_preempt_exp_mutex.
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*/
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static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp)
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{
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unsigned long flags;
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unsigned long mask;
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spin_lock_irqsave(&rnp->lock, flags);
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for (;;) {
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if (!sync_rcu_preempt_exp_done(rnp))
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break;
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if (rnp->parent == NULL) {
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wake_up(&sync_rcu_preempt_exp_wq);
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break;
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}
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mask = rnp->grpmask;
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spin_unlock(&rnp->lock); /* irqs remain disabled */
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rnp = rnp->parent;
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spin_lock(&rnp->lock); /* irqs already disabled */
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rnp->expmask &= ~mask;
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}
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spin_unlock_irqrestore(&rnp->lock, flags);
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}
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/*
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* Snapshot the tasks blocking the newly started preemptible-RCU expedited
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* grace period for the specified rcu_node structure. If there are no such
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* tasks, report it up the rcu_node hierarchy.
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*
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* Caller must hold sync_rcu_preempt_exp_mutex and rsp->onofflock.
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*/
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static void
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sync_rcu_preempt_exp_init(struct rcu_state *rsp, struct rcu_node *rnp)
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{
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int must_wait;
|
||||
|
||||
spin_lock(&rnp->lock); /* irqs already disabled */
|
||||
list_splice_init(&rnp->blocked_tasks[0], &rnp->blocked_tasks[2]);
|
||||
list_splice_init(&rnp->blocked_tasks[1], &rnp->blocked_tasks[3]);
|
||||
must_wait = rcu_preempted_readers_exp(rnp);
|
||||
spin_unlock(&rnp->lock); /* irqs remain disabled */
|
||||
if (!must_wait)
|
||||
rcu_report_exp_rnp(rsp, rnp);
|
||||
}
|
||||
|
||||
/*
|
||||
* Wait for an rcu-preempt grace period, but expedite it. The basic idea
|
||||
* is to invoke synchronize_sched_expedited() to push all the tasks to
|
||||
* the ->blocked_tasks[] lists, move all entries from the first set of
|
||||
* ->blocked_tasks[] lists to the second set, and finally wait for this
|
||||
* second set to drain.
|
||||
*/
|
||||
void synchronize_rcu_expedited(void)
|
||||
{
|
||||
synchronize_rcu();
|
||||
unsigned long flags;
|
||||
struct rcu_node *rnp;
|
||||
struct rcu_state *rsp = &rcu_preempt_state;
|
||||
long snap;
|
||||
int trycount = 0;
|
||||
|
||||
smp_mb(); /* Caller's modifications seen first by other CPUs. */
|
||||
snap = ACCESS_ONCE(sync_rcu_preempt_exp_count) + 1;
|
||||
smp_mb(); /* Above access cannot bleed into critical section. */
|
||||
|
||||
/*
|
||||
* Acquire lock, falling back to synchronize_rcu() if too many
|
||||
* lock-acquisition failures. Of course, if someone does the
|
||||
* expedited grace period for us, just leave.
|
||||
*/
|
||||
while (!mutex_trylock(&sync_rcu_preempt_exp_mutex)) {
|
||||
if (trycount++ < 10)
|
||||
udelay(trycount * num_online_cpus());
|
||||
else {
|
||||
synchronize_rcu();
|
||||
return;
|
||||
}
|
||||
if ((ACCESS_ONCE(sync_rcu_preempt_exp_count) - snap) > 0)
|
||||
goto mb_ret; /* Others did our work for us. */
|
||||
}
|
||||
if ((ACCESS_ONCE(sync_rcu_preempt_exp_count) - snap) > 0)
|
||||
goto unlock_mb_ret; /* Others did our work for us. */
|
||||
|
||||
/* force all RCU readers onto blocked_tasks[]. */
|
||||
synchronize_sched_expedited();
|
||||
|
||||
spin_lock_irqsave(&rsp->onofflock, flags);
|
||||
|
||||
/* Initialize ->expmask for all non-leaf rcu_node structures. */
|
||||
rcu_for_each_nonleaf_node_breadth_first(rsp, rnp) {
|
||||
spin_lock(&rnp->lock); /* irqs already disabled. */
|
||||
rnp->expmask = rnp->qsmaskinit;
|
||||
spin_unlock(&rnp->lock); /* irqs remain disabled. */
|
||||
}
|
||||
|
||||
/* Snapshot current state of ->blocked_tasks[] lists. */
|
||||
rcu_for_each_leaf_node(rsp, rnp)
|
||||
sync_rcu_preempt_exp_init(rsp, rnp);
|
||||
if (NUM_RCU_NODES > 1)
|
||||
sync_rcu_preempt_exp_init(rsp, rcu_get_root(rsp));
|
||||
|
||||
spin_unlock_irqrestore(&rsp->onofflock, flags);
|
||||
|
||||
/* Wait for snapshotted ->blocked_tasks[] lists to drain. */
|
||||
rnp = rcu_get_root(rsp);
|
||||
wait_event(sync_rcu_preempt_exp_wq,
|
||||
sync_rcu_preempt_exp_done(rnp));
|
||||
|
||||
/* Clean up and exit. */
|
||||
smp_mb(); /* ensure expedited GP seen before counter increment. */
|
||||
ACCESS_ONCE(sync_rcu_preempt_exp_count)++;
|
||||
unlock_mb_ret:
|
||||
mutex_unlock(&sync_rcu_preempt_exp_mutex);
|
||||
mb_ret:
|
||||
smp_mb(); /* ensure subsequent action seen after grace period. */
|
||||
}
|
||||
EXPORT_SYMBOL_GPL(synchronize_rcu_expedited);
|
||||
|
||||
|
@ -655,6 +821,20 @@ void synchronize_rcu_expedited(void)
|
|||
}
|
||||
EXPORT_SYMBOL_GPL(synchronize_rcu_expedited);
|
||||
|
||||
#ifdef CONFIG_HOTPLUG_CPU
|
||||
|
||||
/*
|
||||
* Because preemptable RCU does not exist, there is never any need to
|
||||
* report on tasks preempted in RCU read-side critical sections during
|
||||
* expedited RCU grace periods.
|
||||
*/
|
||||
static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp)
|
||||
{
|
||||
return;
|
||||
}
|
||||
|
||||
#endif /* #ifdef CONFIG_HOTPLUG_CPU */
|
||||
|
||||
/*
|
||||
* Because preemptable RCU does not exist, it never has any work to do.
|
||||
*/
|
||||
|
|
|
@ -157,6 +157,7 @@ static void print_one_rcu_state(struct seq_file *m, struct rcu_state *rsp)
|
|||
{
|
||||
long gpnum;
|
||||
int level = 0;
|
||||
int phase;
|
||||
struct rcu_node *rnp;
|
||||
|
||||
gpnum = rsp->gpnum;
|
||||
|
@ -173,10 +174,13 @@ static void print_one_rcu_state(struct seq_file *m, struct rcu_state *rsp)
|
|||
seq_puts(m, "\n");
|
||||
level = rnp->level;
|
||||
}
|
||||
seq_printf(m, "%lx/%lx %c>%c %d:%d ^%d ",
|
||||
phase = gpnum & 0x1;
|
||||
seq_printf(m, "%lx/%lx %c%c>%c%c %d:%d ^%d ",
|
||||
rnp->qsmask, rnp->qsmaskinit,
|
||||
"T."[list_empty(&rnp->blocked_tasks[gpnum & 1])],
|
||||
"T."[list_empty(&rnp->blocked_tasks[!(gpnum & 1)])],
|
||||
"T."[list_empty(&rnp->blocked_tasks[phase])],
|
||||
"E."[list_empty(&rnp->blocked_tasks[phase + 2])],
|
||||
"T."[list_empty(&rnp->blocked_tasks[!phase])],
|
||||
"E."[list_empty(&rnp->blocked_tasks[!phase + 2])],
|
||||
rnp->grplo, rnp->grphi, rnp->grpnum);
|
||||
}
|
||||
seq_puts(m, "\n");
|
||||
|
|
Loading…
Reference in a new issue