From: Alexander Gordeev <agordeev@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: Alexander Gordeev <agordeev@redhat.com>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Steven Rostedt <rostedt@goodmis.org>
Subject: [PATCH v2 1/9] rcu: Panic if RCU tree can not accommodate all CPUs
Date: Fri, 29 May 2015 11:53:37 +0200 [thread overview]
Message-ID: <1e5e5cf188c90193dc176caa5b6270606ae7af5b.1432889921.git.agordeev@redhat.com> (raw)
In-Reply-To: <cover.1432889921.git.agordeev@redhat.com>
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@linux.vnet.ibm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Alexander Gordeev <agordeev@redhat.com>
---
kernel/rcu/tree.c | 15 +++++++++------
1 file changed, 9 insertions(+), 6 deletions(-)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 2fce662..66a4230 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -4117,16 +4117,19 @@ static void __init rcu_init_geometry(void)
rcu_capacity[i] = rcu_capacity[i - 1] * RCU_FANOUT;
/*
+ * The tree must be able to accommodate the configured number of CPUs.
+ * If this limit is exceeded than we have a serious problem elsewhere.
+ *
* 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 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 ||
- n > rcu_capacity[MAX_RCU_LVLS]) {
+ if (n > rcu_capacity[MAX_RCU_LVLS])
+ panic("rcu_init_geometry: rcu_capacity[] is too small");
+ else if (rcu_fanout_leaf < RCU_FANOUT_LEAF ||
+ rcu_fanout_leaf > sizeof(unsigned long) * 8) {
WARN_ON(1);
return;
}
--
1.8.3.1
next prev parent reply other threads:[~2015-05-29 9:54 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-29 9:53 [PATCH v2 0/9] rcu: Cleanup RCU tree initialization Alexander Gordeev
2015-05-29 9:53 ` Alexander Gordeev [this message]
2015-06-01 18:37 ` [PATCH v2 1/9] rcu: Panic if RCU tree can not accommodate all CPUs Paul E. McKenney
2015-06-02 6:45 ` Alexander Gordeev
2015-06-02 12:37 ` Paul E. McKenney
2015-05-29 9:53 ` [PATCH v2 2/9] rcu: Remove superfluous local variable in rcu_init_geometry() Alexander Gordeev
2015-05-29 9:53 ` [PATCH v2 3/9] rcu: Cleanup rcu_init_geometry() code and arithmetics Alexander Gordeev
2015-05-29 9:53 ` [PATCH v2 4/9] rcu: Simplify rcu_init_geometry() capacity arithmetics Alexander Gordeev
2015-05-29 9:53 ` [PATCH v2 5/9] rcu: Limit rcu_state::levelcnt[] to RCU_NUM_LVLS items Alexander Gordeev
2015-05-29 9:53 ` [PATCH v2 6/9] rcu: Limit rcu_capacity[] size " Alexander Gordeev
2015-05-29 9:53 ` [PATCH v2 7/9] rcu: Remove unnecessary fields from rcu_state structure Alexander Gordeev
2015-05-29 9:53 ` [PATCH v2 8/9] rcu: Limit count of static data to the number of RCU levels Alexander Gordeev
2015-05-29 9:53 ` [PATCH v2 9/9] rcu: Simplify arithmetic to calculate number of RCU nodes Alexander Gordeev
2015-06-01 18:58 ` [PATCH v2 0/9] rcu: Cleanup RCU tree initialization Paul E. McKenney
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