From cdfa0f6fa6b7183c062046043b649b9a91e3ac52 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Mon, 3 Apr 2023 16:49:14 -0700 Subject: [PATCH] rcu/kvfree: Add debug to check grace periods This commit adds debugging checks to verify that the required RCU grace period has elapsed for each kvfree_rcu_bulk_data structure that arrives at the kvfree_rcu_bulk() function. These checks make use of that structure's ->gp_snap field, which has been upgraded from an unsigned long to an rcu_gp_oldstate structure. This upgrade reduces the chances of false positives to nearly zero, even on 32-bit systems, for which this structure carries 64 bits of state. Cc: Ziwei Dai Signed-off-by: Paul E. McKenney --- kernel/rcu/tree.c | 37 +++++++++++++++++++------------------ 1 file changed, 19 insertions(+), 18 deletions(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index f52ff72..91d75fd 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -2756,7 +2756,7 @@ EXPORT_SYMBOL_GPL(call_rcu); */ struct kvfree_rcu_bulk_data { struct list_head list; - unsigned long gp_snap; + struct rcu_gp_oldstate gp_snap; unsigned long nr_records; void *records[]; }; @@ -2921,23 +2921,24 @@ kvfree_rcu_bulk(struct kfree_rcu_cpu *krcp, int i; debug_rcu_bhead_unqueue(bnode); - - rcu_lock_acquire(&rcu_callback_map); - if (idx == 0) { // kmalloc() / kfree(). - trace_rcu_invoke_kfree_bulk_callback( - rcu_state.name, bnode->nr_records, - bnode->records); - - kfree_bulk(bnode->nr_records, bnode->records); - } else { // vmalloc() / vfree(). - for (i = 0; i < bnode->nr_records; i++) { - trace_rcu_invoke_kvfree_callback( - rcu_state.name, bnode->records[i], 0); - - vfree(bnode->records[i]); + if (!WARN_ON_ONCE(!poll_state_synchronize_rcu_full(&bnode->gp_snap))) { + rcu_lock_acquire(&rcu_callback_map); + if (idx == 0) { // kmalloc() / kfree(). + trace_rcu_invoke_kfree_bulk_callback( + rcu_state.name, bnode->nr_records, + bnode->records); + + kfree_bulk(bnode->nr_records, bnode->records); + } else { // vmalloc() / vfree(). + for (i = 0; i < bnode->nr_records; i++) { + trace_rcu_invoke_kvfree_callback( + rcu_state.name, bnode->records[i], 0); + + vfree(bnode->records[i]); + } } + rcu_lock_release(&rcu_callback_map); } - rcu_lock_release(&rcu_callback_map); raw_spin_lock_irqsave(&krcp->lock, flags); if (put_cached_bnode(krcp, bnode)) @@ -3081,7 +3082,7 @@ kvfree_rcu_drain_ready(struct kfree_rcu_cpu *krcp) INIT_LIST_HEAD(&bulk_ready[i]); list_for_each_entry_safe_reverse(bnode, n, &krcp->bulk_head[i], list) { - if (!poll_state_synchronize_rcu(bnode->gp_snap)) + if (!poll_state_synchronize_rcu_full(&bnode->gp_snap)) break; atomic_sub(bnode->nr_records, &krcp->bulk_count[i]); @@ -3285,7 +3286,7 @@ add_ptr_to_bulk_krc_lock(struct kfree_rcu_cpu **krcp, // Finally insert and update the GP for this page. bnode->records[bnode->nr_records++] = ptr; - bnode->gp_snap = get_state_synchronize_rcu(); + get_state_synchronize_rcu_full(&bnode->gp_snap); atomic_inc(&(*krcp)->bulk_count[idx]); return true; -- 2.7.4