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From: paulmck@kernel.org
To: rcu@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com,
	mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com,
	akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
	josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org,
	rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com,
	fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org,
	Uladzislau Rezki <urezki@gmail.com>,
	"Paul E . McKenney" <paulmck@kernel.org>
Subject: [PATCH tip/core/rcu 05/17] rcu/tree: Make debug_objects logic independent of rcu_head
Date: Wed, 24 Jun 2020 13:12:14 -0700
Message-ID: <20200624201226.21197-5-paulmck@kernel.org> (raw)
In-Reply-To: <20200624201200.GA28901@paulmck-ThinkPad-P72>

From: "Joel Fernandes (Google)" <joel@joelfernandes.org>

kfree_rcu()'s debug_objects logic uses the address of the object's
embedded rcu_head to queue/unqueue. Instead of this, make use of the
object's address itself as preparation for future headless kfree_rcu()
support.

Reviewed-by: Uladzislau Rezki <urezki@gmail.com>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/rcu/tree.c | 29 +++++++++++++----------------
 1 file changed, 13 insertions(+), 16 deletions(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 31d3b2c..dc5369a 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2952,13 +2952,11 @@ EXPORT_SYMBOL_GPL(call_rcu);
  * @nr_records: Number of active pointers in the array
  * @records: Array of the kfree_rcu() pointers
  * @next: Next bulk object in the block chain
- * @head_free_debug: For debug, when CONFIG_DEBUG_OBJECTS_RCU_HEAD is set
  */
 struct kfree_rcu_bulk_data {
 	unsigned long nr_records;
 	void *records[KFREE_BULK_MAX_ENTR];
 	struct kfree_rcu_bulk_data *next;
-	struct rcu_head *head_free_debug;
 };
 
 /**
@@ -3008,11 +3006,13 @@ struct kfree_rcu_cpu {
 static DEFINE_PER_CPU(struct kfree_rcu_cpu, krc);
 
 static __always_inline void
-debug_rcu_head_unqueue_bulk(struct rcu_head *head)
+debug_rcu_bhead_unqueue(struct kfree_rcu_bulk_data *bhead)
 {
 #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
-	for (; head; head = head->next)
-		debug_rcu_head_unqueue(head);
+	int i;
+
+	for (i = 0; i < bhead->nr_records; i++)
+		debug_rcu_head_unqueue((struct rcu_head *)(bhead->records[i]));
 #endif
 }
 
@@ -3042,7 +3042,7 @@ static void kfree_rcu_work(struct work_struct *work)
 	for (; bhead; bhead = bnext) {
 		bnext = bhead->next;
 
-		debug_rcu_head_unqueue_bulk(bhead->head_free_debug);
+		debug_rcu_bhead_unqueue(bhead);
 
 		rcu_lock_acquire(&rcu_callback_map);
 		trace_rcu_invoke_kfree_bulk_callback(rcu_state.name,
@@ -3064,14 +3064,15 @@ static void kfree_rcu_work(struct work_struct *work)
 	 */
 	for (; head; head = next) {
 		unsigned long offset = (unsigned long)head->func;
+		void *ptr = (void *)head - offset;
 
 		next = head->next;
-		debug_rcu_head_unqueue(head);
+		debug_rcu_head_unqueue((struct rcu_head *)ptr);
 		rcu_lock_acquire(&rcu_callback_map);
 		trace_rcu_invoke_kfree_callback(rcu_state.name, head, offset);
 
 		if (!WARN_ON_ONCE(!__is_kfree_rcu_offset(offset)))
-			kfree((void *)head - offset);
+			kfree(ptr);
 
 		rcu_lock_release(&rcu_callback_map);
 		cond_resched_tasks_rcu_qs();
@@ -3210,18 +3211,11 @@ kfree_call_rcu_add_ptr_to_bulk(struct kfree_rcu_cpu *krcp,
 		/* Initialize the new block. */
 		bnode->nr_records = 0;
 		bnode->next = krcp->bhead;
-		bnode->head_free_debug = NULL;
 
 		/* Attach it to the head. */
 		krcp->bhead = bnode;
 	}
 
-#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
-	head->func = func;
-	head->next = krcp->bhead->head_free_debug;
-	krcp->bhead->head_free_debug = head;
-#endif
-
 	/* Finally insert. */
 	krcp->bhead->records[krcp->bhead->nr_records++] =
 		(void *) head - (unsigned long) func;
@@ -3245,14 +3239,17 @@ void kfree_call_rcu(struct rcu_head *head, rcu_callback_t func)
 {
 	unsigned long flags;
 	struct kfree_rcu_cpu *krcp;
+	void *ptr;
 
 	local_irq_save(flags);	// For safely calling this_cpu_ptr().
 	krcp = this_cpu_ptr(&krc);
 	if (krcp->initialized)
 		raw_spin_lock(&krcp->lock);
 
+	ptr = (void *)head - (unsigned long)func;
+
 	// Queue the object but don't yet schedule the batch.
-	if (debug_rcu_head_queue(head)) {
+	if (debug_rcu_head_queue(ptr)) {
 		// Probable double kfree_rcu(), just leak.
 		WARN_ONCE(1, "%s(): Double-freed call. rcu_head %p\n",
 			  __func__, head);
-- 
2.9.5


  parent reply index

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-24 20:12 [PATCH tip/core/rcu 0/17] kfree_rcu updates for v5.9 Paul E. McKenney
2020-06-24 20:12 ` [PATCH tip/core/rcu 01/17] rcu: Fix a kernel-doc warnings for "count" paulmck
2020-06-24 20:12 ` [PATCH tip/core/rcu 02/17] rcu/tree: Keep kfree_rcu() awake during lock contention paulmck
2020-06-24 20:12 ` [PATCH tip/core/rcu 03/17] rcu/tree: Skip entry into the page allocator for PREEMPT_RT paulmck
2020-06-30 16:45   ` Sebastian Andrzej Siewior
2020-06-30 18:35     ` Paul E. McKenney
2020-07-02 14:12       ` Sebastian Andrzej Siewior
2020-07-02 16:48         ` Paul E. McKenney
2020-07-02 20:19           ` Sebastian Andrzej Siewior
2020-07-06 21:06             ` Paul E. McKenney
2020-07-02 19:45         ` Uladzislau Rezki
2020-07-06 19:42           ` Joel Fernandes
2020-07-06 19:55             ` Uladzislau Rezki
2020-07-06 20:29               ` Joel Fernandes
2020-06-24 20:12 ` [PATCH tip/core/rcu 04/17] rcu/tree: Repeat the monitor if any free channel is busy paulmck
2020-06-24 20:12 ` paulmck [this message]
2020-06-24 20:12 ` [PATCH tip/core/rcu 06/17] rcu/tree: Simplify KFREE_BULK_MAX_ENTR macro paulmck
2020-06-24 20:12 ` [PATCH tip/core/rcu 07/17] rcu/tree: Move kfree_rcu_cpu locking/unlocking to separate functions paulmck
2020-06-24 20:12 ` [PATCH tip/core/rcu 08/17] rcu/tree: Use static initializer for krc.lock paulmck
2020-06-24 20:12 ` [PATCH tip/core/rcu 09/17] rcu/tree: cache specified number of objects paulmck
2020-06-24 20:12 ` [PATCH tip/core/rcu 10/17] rcu/tree: Maintain separate array for vmalloc ptrs paulmck
2020-06-24 20:12 ` [PATCH tip/core/rcu 11/17] rcu/tiny: support vmalloc in tiny-RCU paulmck
2020-06-24 20:12 ` [PATCH tip/core/rcu 12/17] rcu: Rename *_kfree_callback/*_kfree_rcu_offset/kfree_call_* paulmck
2020-06-24 20:12 ` [PATCH tip/core/rcu 13/17] mm/list_lru.c: Rename kvfree_rcu() to local variant paulmck
2020-06-24 20:12 ` [PATCH tip/core/rcu 14/17] rcu: Introduce 2 arg kvfree_rcu() interface paulmck
2020-06-24 20:12 ` [PATCH tip/core/rcu 15/17] rcu: Support reclaim for head-less object paulmck
2020-06-24 20:12 ` [PATCH tip/core/rcu 16/17] rcu: Introduce single argument kvfree_rcu() interface paulmck
2020-06-24 20:12 ` [PATCH tip/core/rcu 17/17] lib/test_vmalloc.c: Add test cases for kvfree_rcu() paulmck

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