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authorPaul E. McKenney2019-12-15 11:38:57 -0800
committerPaul E. McKenney2020-02-20 15:58:21 -0800
commit82dd8419e225958f01708cda8a3fc6c3c5356228 (patch)
treed11b6e4bf1cbcbeaf29bc916762b2fdbaf24c3f1 /kernel
parent9f01eb5d4936f12d57da84cdfbc2a3623e23a7eb (diff)
rcu: Warn on for_each_leaf_node_cpu_mask() from non-leaf
The for_each_leaf_node_cpu_mask() and for_each_leaf_node_possible_cpu() macros must be invoked only on leaf rcu_node structures. Failing to abide by this restriction can result in infinite loops on systems with more than 64 CPUs (or for more than 32 CPUs on 32-bit systems). This commit therefore adds WARN_ON_ONCE() calls to make misuse of these two macros easier to debug. Reported-by: Qian Cai <cai@lca.pw> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/rcu/rcu.h6
1 files changed, 4 insertions, 2 deletions
diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h
index 05f936ed167a..f6ce173e35f6 100644
--- a/kernel/rcu/rcu.h
+++ b/kernel/rcu/rcu.h
@@ -325,7 +325,8 @@ static inline void rcu_init_levelspread(int *levelspread, const int *levelcnt)
* Iterate over all possible CPUs in a leaf RCU node.
*/
#define for_each_leaf_node_possible_cpu(rnp, cpu) \
- for ((cpu) = cpumask_next((rnp)->grplo - 1, cpu_possible_mask); \
+ for (WARN_ON_ONCE(!rcu_is_leaf_node(rnp)), \
+ (cpu) = cpumask_next((rnp)->grplo - 1, cpu_possible_mask); \
(cpu) <= rnp->grphi; \
(cpu) = cpumask_next((cpu), cpu_possible_mask))
@@ -335,7 +336,8 @@ static inline void rcu_init_levelspread(int *levelspread, const int *levelcnt)
#define rcu_find_next_bit(rnp, cpu, mask) \
((rnp)->grplo + find_next_bit(&(mask), BITS_PER_LONG, (cpu)))
#define for_each_leaf_node_cpu_mask(rnp, cpu, mask) \
- for ((cpu) = rcu_find_next_bit((rnp), 0, (mask)); \
+ for (WARN_ON_ONCE(!rcu_is_leaf_node(rnp)), \
+ (cpu) = rcu_find_next_bit((rnp), 0, (mask)); \
(cpu) <= rnp->grphi; \
(cpu) = rcu_find_next_bit((rnp), (cpu) + 1 - (rnp->grplo), (mask)))