Skip to content

Commit

Permalink
rcu: Add WARN_ON_ONCE() consistency checks covering state transitions
Browse files Browse the repository at this point in the history 
o Verify that qsmask bits stay clear through GP
  initialization.

o Verify that cpu_quiet_msk_finish() is never invoked unless
  there actually is an RCU grace period in progress.

o Verify that all internal-node rcu_node structures have empty
  blocked_tasks[] lists.

o Verify that child rcu_node structure's bits remain clear after
  acquiring parent's lock.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: akpm@linux-foundation.org
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
LKML-Reference: <12532926191947-git-send-email->
Signed-off-by: Ingo Molnar <mingo@elte.hu>
  • Loading branch information
@paulmck
paulmck authored and Ingo Molnar committed Sep 19, 2009
1 parent 16e3081 commit 28ecd58
Show file tree
Hide file tree
Showing 2 changed files with 23 additions and 10 deletions.
13 changes: 9 additions & 4 deletions kernel/rcutree.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -628,8 +628,8 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags)

/* Special-case the common single-level case. */
if (NUM_RCU_NODES == 1) {
rnp->qsmask = rnp->qsmaskinit;
rcu_preempt_check_blocked_tasks(rnp);
rnp->qsmask = rnp->qsmaskinit;
rnp->gpnum = rsp->gpnum;
rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state OK. */
spin_unlock_irqrestore(&rnp->lock, flags);
Expand Down Expand Up @@ -662,8 +662,8 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
rnp_end = &rsp->node[NUM_RCU_NODES];
for (rnp_cur = &rsp->node[0]; rnp_cur < rnp_end; rnp_cur++) {
spin_lock(&rnp_cur->lock); /* irqs already disabled. */
rnp_cur->qsmask = rnp_cur->qsmaskinit;
rcu_preempt_check_blocked_tasks(rnp);
rnp_cur->qsmask = rnp_cur->qsmaskinit;
rnp->gpnum = rsp->gpnum;
spin_unlock(&rnp_cur->lock); /* irqs already disabled. */
}
Expand Down Expand Up @@ -708,6 +708,7 @@ rcu_process_gp_end(struct rcu_state *rsp, struct rcu_data *rdp)
static void cpu_quiet_msk_finish(struct rcu_state *rsp, unsigned long flags)
__releases(rnp->lock)
{
WARN_ON_ONCE(rsp->completed == rsp->gpnum);
rsp->completed = rsp->gpnum;
rcu_process_gp_end(rsp, rsp->rda[smp_processor_id()]);
rcu_start_gp(rsp, flags); /* releases root node's rnp->lock. */
Expand All @@ -725,6 +726,8 @@ cpu_quiet_msk(unsigned long mask, struct rcu_state *rsp, struct rcu_node *rnp,
unsigned long flags)
__releases(rnp->lock)
{
struct rcu_node *rnp_c;

/* Walk up the rcu_node hierarchy. */
for (;;) {
if (!(rnp->qsmask & mask)) {
Expand All @@ -748,8 +751,10 @@ cpu_quiet_msk(unsigned long mask, struct rcu_state *rsp, struct rcu_node *rnp,
break;
}
spin_unlock_irqrestore(&rnp->lock, flags);
rnp_c = rnp;
rnp = rnp->parent;
spin_lock_irqsave(&rnp->lock, flags);
WARN_ON_ONCE(rnp_c->qsmask);
}

/*
Expand Down Expand Up @@ -858,7 +863,7 @@ static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp)
spin_lock_irqsave(&rsp->onofflock, flags);

/* Remove the outgoing CPU from the masks in the rcu_node hierarchy. */
rnp = rdp->mynode;
rnp = rdp->mynode; /* this is the outgoing CPU's rnp. */
mask = rdp->grpmask; /* rnp->grplo is constant. */
do {
spin_lock(&rnp->lock); /* irqs already disabled. */
Expand All @@ -867,7 +872,7 @@ static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp)
spin_unlock(&rnp->lock); /* irqs remain disabled. */
break;
}
rcu_preempt_offline_tasks(rsp, rnp);
rcu_preempt_offline_tasks(rsp, rnp, rdp);
mask = rnp->grpmask;
spin_unlock(&rnp->lock); /* irqs remain disabled. */
rnp = rnp->parent;
Expand Down
20 changes: 14 additions & 6 deletions kernel/rcutree_plugin.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -206,7 +206,8 @@ static void rcu_read_unlock_special(struct task_struct *t)
*/
if (!empty && rnp->qsmask == 0 &&
list_empty(&rnp->blocked_tasks[rnp->gpnum & 0x1])) {
t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_NEED_QS;
struct rcu_node *rnp_p;

if (rnp->parent == NULL) {
/* Only one rcu_node in the tree. */
cpu_quiet_msk_finish(&rcu_preempt_state, flags);
Expand All @@ -215,9 +216,10 @@ static void rcu_read_unlock_special(struct task_struct *t)
/* Report up the rest of the hierarchy. */
mask = rnp->grpmask;
spin_unlock_irqrestore(&rnp->lock, flags);
rnp = rnp->parent;
spin_lock_irqsave(&rnp->lock, flags);
cpu_quiet_msk(mask, &rcu_preempt_state, rnp, flags);
rnp_p = rnp->parent;
spin_lock_irqsave(&rnp_p->lock, flags);
WARN_ON_ONCE(rnp->qsmask);
cpu_quiet_msk(mask, &rcu_preempt_state, rnp_p, flags);
return;
}
spin_unlock(&rnp->lock);
Expand Down Expand Up @@ -278,6 +280,7 @@ static void rcu_print_task_stall(struct rcu_node *rnp)
static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp)
{
WARN_ON_ONCE(!list_empty(&rnp->blocked_tasks[rnp->gpnum & 0x1]));
WARN_ON_ONCE(rnp->qsmask);
}

/*
Expand All @@ -302,7 +305,8 @@ static int rcu_preempted_readers(struct rcu_node *rnp)
* The caller must hold rnp->lock with irqs disabled.
*/
static void rcu_preempt_offline_tasks(struct rcu_state *rsp,
struct rcu_node *rnp)
struct rcu_node *rnp,
struct rcu_data *rdp)
{
int i;
struct list_head *lp;
Expand All @@ -314,6 +318,9 @@ static void rcu_preempt_offline_tasks(struct rcu_state *rsp,
WARN_ONCE(1, "Last CPU thought to be offlined?");
return; /* Shouldn't happen: at least one CPU online. */
}
WARN_ON_ONCE(rnp != rdp->mynode &&
(!list_empty(&rnp->blocked_tasks[0]) ||
!list_empty(&rnp->blocked_tasks[1])));

/*
* Move tasks up to root rcu_node. Rely on the fact that the
Expand Down Expand Up @@ -489,7 +496,8 @@ static int rcu_preempted_readers(struct rcu_node *rnp)
* tasks that were blocked within RCU read-side critical sections.
*/
static void rcu_preempt_offline_tasks(struct rcu_state *rsp,
struct rcu_node *rnp)
struct rcu_node *rnp,
struct rcu_data *rdp)
{
}

Expand Down

0 comments on commit 28ecd58

Please sign in to comment.