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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@linux.vnet.ibm.com> Cc: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Alexander Gordeev <agordeev@redhat.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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319362c90f
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1 changed files with 17 additions and 12 deletions
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@ -4106,6 +4106,19 @@ static void __init rcu_init_geometry(void)
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pr_info("RCU: Adjusting geometry for rcu_fanout_leaf=%d, nr_cpu_ids=%d\n",
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rcu_fanout_leaf, nr_cpu_ids);
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/*
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* The boot-time rcu_fanout_leaf parameter is only permitted
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* to increase the leaf-level fanout, not decrease it. Of course,
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* the leaf-level fanout cannot exceed the number of bits in
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* the rcu_node masks. Complain and fall back to the compile-
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* time values if these limits are exceeded.
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*/
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if (rcu_fanout_leaf < RCU_FANOUT_LEAF ||
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rcu_fanout_leaf > sizeof(unsigned long) * 8) {
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WARN_ON(1);
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return;
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}
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/*
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* Compute number of nodes that can be handled an rcu_node tree
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* with the given number of levels. Setting rcu_capacity[0] makes
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@ -4117,19 +4130,11 @@ static void __init rcu_init_geometry(void)
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rcu_capacity[i] = rcu_capacity[i - 1] * RCU_FANOUT;
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/*
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* The boot-time rcu_fanout_leaf parameter is only permitted
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* to increase the leaf-level fanout, not decrease it. Of course,
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* the leaf-level fanout cannot exceed the number of bits in
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* the rcu_node masks. Finally, the tree must be able to accommodate
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* the configured number of CPUs. Complain and fall back to the
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* compile-time values if these limits are exceeded.
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* The tree must be able to accommodate the configured number of CPUs.
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* If this limit is exceeded than we have a serious problem elsewhere.
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*/
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if (rcu_fanout_leaf < RCU_FANOUT_LEAF ||
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rcu_fanout_leaf > sizeof(unsigned long) * 8 ||
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n > rcu_capacity[MAX_RCU_LVLS]) {
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WARN_ON(1);
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return;
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}
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if (n > rcu_capacity[MAX_RCU_LVLS])
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panic("rcu_init_geometry: rcu_capacity[] is too small");
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/* Calculate the number of rcu_nodes at each level of the tree. */
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for (i = 1; i <= MAX_RCU_LVLS; i++)
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