Messages in this thread Patch in this message | | | From | Alexander Gordeev <> | Subject | [PATCH v2 1/9] rcu: Panic if RCU tree can not accommodate all CPUs | Date | Fri, 29 May 2015 11:53:37 +0200 |
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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
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