Commit-ID: 75cf15a4c0dd57f5d230bd30c2d41bd8e06ae5a9
Gitweb: http://git.kernel.org/tip/75cf15a4c0dd57f5d230bd30c2d41bd8e06ae5a9
Author: Alexander Gordeev <agordeev@xxxxxxxxxx>
AuthorDate: Wed, 3 Jun 2015 08:18:23 +0200
Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CommitDate: Wed, 15 Jul 2015 14:45:12 -0700
rcu: Panic if RCU tree can not accommodate all CPUs
Currently a condition when RCU tree is unable to accommodate
the configured number of CPUs is not permitted and causes
a fall back to compile-time values. However, the code has no
means to exceed the RCU tree capacity neither at compile-time
nor in run-time. Therefore, if the condition is met in run-
time then it indicates a serios problem elsewhere and should
be handled with a panic.
Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Signed-off-by: Alexander Gordeev <agordeev@xxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
---
kernel/rcu/tree.c | 29 +++++++++++++++++------------
1 file changed, 17 insertions(+), 12 deletions(-)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 1c58cbd..fe8d929 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -4107,6 +4107,19 @@ static void __init rcu_init_geometry(void)
rcu_fanout_leaf, nr_cpu_ids);
/*
+ * The boot-time rcu_fanout_leaf parameter is only permitted
+ * to increase the leaf-level fanout, not decrease it. Of course,
+ * the leaf-level fanout cannot exceed the number of bits in
+ * the rcu_node masks. Complain and fall back to the compile-
+ * time values if these limits are exceeded.
+ */
+ if (rcu_fanout_leaf < RCU_FANOUT_LEAF ||
+ rcu_fanout_leaf > sizeof(unsigned long) * 8) {
+ WARN_ON(1);
+ return;
+ }
+
+ /*
* Compute number of nodes that can be handled an rcu_node tree
* with the given number of levels. Setting rcu_capacity[0] makes
* some of the arithmetic easier.
@@ -4117,19 +4130,11 @@ static void __init rcu_init_geometry(void)
rcu_capacity[i] = rcu_capacity[i - 1] * RCU_FANOUT;
/*
- * The boot-time rcu_fanout_leaf parameter is only permitted
- * to increase the leaf-level fanout, not decrease it. Of course,
- * the leaf-level fanout cannot exceed the number of bits in
- * the rcu_node masks. Finally, the tree must be able to accommodate
- * the configured number of CPUs. Complain and fall back to the
- * compile-time values if these limits are exceeded.
+ * The tree must be able to accommodate the configured number of CPUs.
+ * If this limit is exceeded than we have a serious problem elsewhere.
*/
- if (rcu_fanout_leaf < RCU_FANOUT_LEAF ||
- rcu_fanout_leaf > sizeof(unsigned long) * 8 ||
- n > rcu_capacity[MAX_RCU_LVLS]) {
- WARN_ON(1);
- return;
- }
+ if (n > rcu_capacity[MAX_RCU_LVLS])
+ panic("rcu_init_geometry: rcu_capacity[] is too small");
/* Calculate the number of rcu_nodes at each level of the tree. */
for (i = 1; i <= MAX_RCU_LVLS; i++)
--
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