From: "Joel Fernandes (Google)" <joel@joelfernandes.org>
To: linux-kernel@vger.kernel.org
Cc: "Joel Fernandes (Google)" <joel@joelfernandes.org>,
Andrew Morton <akpm@linux-foundation.org>,
Davidlohr Bueso <dave@stgolabs.net>,
Ingo Molnar <mingo@redhat.com>,
Josh Triplett <josh@joshtriplett.org>,
Lai Jiangshan <jiangshanlai@gmail.com>,
linux-mm@kvack.org,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
"Paul E. McKenney" <paulmck@kernel.org>,
rcu@vger.kernel.org, Sakari Ailus <sakari.ailus@linux.intel.com>,
Steven Rostedt <rostedt@goodmis.org>,
"Uladzislau Rezki (Sony)" <urezki@gmail.com>
Subject: [RFC] Simplify debug_objects handling in kfree_rcu
Date: Mon, 16 Mar 2020 13:42:18 -0400 [thread overview]
Message-ID: <20200316174218.154090-1-joel@joelfernandes.org> (raw)
In order to prepare for future changes to headless RCU support, make the
debug_objects handling in kfree_rcu use the final 'pointer' value of the
object, instead of depending on the head.
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
---
Paul, Vlad, I am adding this to my rcu/kfree tree for further testing. Let me know any
comments. I have only build-tested this patch.
kernel/rcu/tree.c | 30 +++++++++++++-----------------
1 file changed, 13 insertions(+), 17 deletions(-)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 32152be9a09ac..0e2632622176b 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2758,7 +2758,6 @@ 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;
};
/**
@@ -2808,11 +2807,11 @@ 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);
+ for (int i = 0; i < bhead->nr_records; i++)
+ debug_rcu_head_unqueue((struct rcu_head *)(bhead->records[i]));
#endif
}
@@ -2842,7 +2841,7 @@ 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,
@@ -2864,14 +2863,15 @@ 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_kvfree_callback(rcu_state.name, head, offset);
if (!WARN_ON_ONCE(!__is_kvfree_rcu_offset(offset)))
- kvfree((void *)head - offset);
+ kvfree(ptr);
rcu_lock_release(&rcu_callback_map);
cond_resched_tasks_rcu_qs();
@@ -2995,18 +2995,11 @@ 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;
@@ -3030,14 +3023,17 @@ void kvfree_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)
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);
@@ -3054,8 +3050,8 @@ void kvfree_call_rcu(struct rcu_head *head, rcu_callback_t func)
* Under high memory pressure GFP_NOWAIT can fail,
* in that case the emergency path is maintained.
*/
- if (is_vmalloc_addr((void *) head - (unsigned long) func) ||
- !kfree_call_rcu_add_ptr_to_bulk(krcp, head, func)) {
+ if (is_vmalloc_addr(ptr) ||
+ !kfree_call_rcu_add_ptr_to_bulk(krcp, head, func)) {
head->func = func;
head->next = krcp->head;
krcp->head = head;
--
2.25.1.481.gfbce0eb801-goog
reply other threads:[~2020-03-16 17:42 UTC|newest]
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