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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2009-09-18 09:50:19 -0700
committerIngo Molnar <mingo@elte.hu>2009-09-19 08:53:21 +0200
commit49e291266d0920264471d9d64268fb030e33a99a (patch)
tree8770717427ee877e6b7b3dae6b120f35be645d70
parente7d8842ed34a7fe19d1ed90f84c211fb056ac523 (diff)
downloadlinux-49e291266d0920264471d9d64268fb030e33a99a.tar.bz2
rcu: Fix thinko, actually initialize full tree
Commit de078d8 ("rcu: Need to update rnp->gpnum if preemptable RCU is to be reliable") repeatedly and incorrectly initializes the root rcu_node structure's ->gpnum field rather than initializing the ->gpnum field of each node in the tree. Fix this. Also add an additional consistency check to catch this in the future. 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: <125329262011-git-send-email-> Signed-off-by: Ingo Molnar <mingo@elte.hu>
-rw-r--r--kernel/rcutree.c11
-rw-r--r--kernel/rcutree_plugin.h4
2 files changed, 7 insertions, 8 deletions
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index ae4a553e37ce..1b32cdd1b2e2 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -601,8 +601,6 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
{
struct rcu_data *rdp = rsp->rda[smp_processor_id()];
struct rcu_node *rnp = rcu_get_root(rsp);
- struct rcu_node *rnp_cur;
- struct rcu_node *rnp_end;
if (!cpu_needs_another_gp(rsp, rdp)) {
spin_unlock_irqrestore(&rnp->lock, flags);
@@ -659,13 +657,12 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
* one corresponding to this CPU, due to the fact that we have
* irqs disabled.
*/
- 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. */
+ for (rnp = &rsp->node[0]; rnp < &rsp->node[NUM_RCU_NODES]; rnp++) {
+ spin_lock(&rnp->lock); /* irqs already disabled. */
rcu_preempt_check_blocked_tasks(rnp);
- rnp_cur->qsmask = rnp_cur->qsmaskinit;
+ rnp->qsmask = rnp->qsmaskinit;
rnp->gpnum = rsp->gpnum;
- spin_unlock(&rnp_cur->lock); /* irqs already disabled. */
+ spin_unlock(&rnp->lock); /* irqs already disabled. */
}
rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state now OK. */
diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index cd6047cc7fc2..09b7325baad1 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -476,10 +476,12 @@ static void rcu_print_task_stall(struct rcu_node *rnp)
/*
* Because there is no preemptable RCU, there can be no readers blocked,
- * so there is no need to check for blocked tasks.
+ * so there is no need to check for blocked tasks. So check only for
+ * bogus qsmask values.
*/
static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp)
{
+ WARN_ON_ONCE(rnp->qsmask);
}
/*