From 309a4316507767f8078d30c9681dc76f4299b0f1 Mon Sep 17 00:00:00 2001 From: Zqiang Date: Sat, 8 Apr 2023 22:25:30 +0800 Subject: [PATCH] rcu/kvfree: Use consistent krcp when growing kfree_rcu() page cache The add_ptr_to_bulk_krc_lock() function is invoked to allocate a new kfree_rcu() page, also known as a kvfree_rcu_bulk_data structure. The kfree_rcu_cpu structure's lock is used to protect this operation, except that this lock must be momentarily dropped when allocating memory. It is clearly important that the lock that is reacquired be the same lock that was acquired initially via krc_this_cpu_lock(). Unfortunately, this same krc_this_cpu_lock() function is used to re-acquire this lock, and if the task migrated to some other CPU during the memory allocation, this will result in the kvfree_rcu_bulk_data structure being added to the wrong CPU's kfree_rcu_cpu structure. This commit therefore replaces that second call to krc_this_cpu_lock() with raw_spin_lock_irqsave() in order to explicitly acquire the lock on the correct kfree_rcu_cpu structure, thus keeping things straight even when the task migrates. Signed-off-by: Zqiang Signed-off-by: Paul E. McKenney --- kernel/rcu/tree.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 426f1f3bb5f28..51d84eabf6453 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -3279,7 +3279,7 @@ add_ptr_to_bulk_krc_lock(struct kfree_rcu_cpu **krcp, // scenarios. bnode = (struct kvfree_rcu_bulk_data *) __get_free_page(GFP_KERNEL | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN); - *krcp = krc_this_cpu_lock(flags); + raw_spin_lock_irqsave(&(*krcp)->lock, *flags); } if (!bnode) -- 2.30.2