From: "Paul E. McKenney" <paulmck@kernel.org>
To: rcu@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com,
rostedt@goodmis.org, "Uladzislau Rezki (Sony)" <urezki@gmail.com>,
"Paul E . McKenney" <paulmck@kernel.org>,
Joel Fernandes <joel@joelfernandes.org>
Subject: [PATCH rcu 1/8] rcu/kvfree: Eliminate k[v]free_rcu() single argument macro
Date: Wed, 10 May 2023 10:02:35 -0700 [thread overview]
Message-ID: <20230510170242.2187714-1-paulmck@kernel.org> (raw)
In-Reply-To: <1c01c38f-3783-44d7-8c11-7416cd5b849c@paulmck-laptop>
From: "Uladzislau Rezki (Sony)" <urezki@gmail.com>
The kvfree_rcu() and kfree_rcu() APIs are hazardous in that if you forget
the second argument, it works, but might sleep. This sleeping can be a
correctness bug from atomic contexts, and even in non-atomic contexts it
might introduce unacceptable latencies. This commit therefore removes the
single-argument kvfree_rcu() and kfree_rcu() macros. Code that would have
previously used these single-argument kvfree_rcu() and kfree_rcu() macros
should instead use kvfree_rcu_mightsleep() or kfree_rcu_mightsleep().
[ paulmck: Apply Joel Fernandes feedback. ]
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
---
include/linux/rcupdate.h | 29 ++++++++---------------------
1 file changed, 8 insertions(+), 21 deletions(-)
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index dcd2cf1e8326..744869ef930a 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -957,9 +957,8 @@ static inline notrace void rcu_read_unlock_sched_notrace(void)
/**
* kfree_rcu() - kfree an object after a grace period.
- * @ptr: pointer to kfree for both single- and double-argument invocations.
- * @rhf: the name of the struct rcu_head within the type of @ptr,
- * but only for double-argument invocations.
+ * @ptr: pointer to kfree for double-argument invocations.
+ * @rhf: the name of the struct rcu_head within the type of @ptr.
*
* Many rcu callbacks functions just call kfree() on the base structure.
* These functions are trivial, but their size adds up, and furthermore
@@ -984,26 +983,18 @@ static inline notrace void rcu_read_unlock_sched_notrace(void)
* The BUILD_BUG_ON check must not involve any function calls, hence the
* checks are done in macros here.
*/
-#define kfree_rcu(ptr, rhf...) kvfree_rcu(ptr, ## rhf)
+#define kfree_rcu(ptr, rhf) kvfree_rcu_arg_2(ptr, rhf)
+#define kvfree_rcu(ptr, rhf) kvfree_rcu_arg_2(ptr, rhf)
/**
- * kvfree_rcu() - kvfree an object after a grace period.
- *
- * This macro consists of one or two arguments and it is
- * based on whether an object is head-less or not. If it
- * has a head then a semantic stays the same as it used
- * to be before:
- *
- * kvfree_rcu(ptr, rhf);
- *
- * where @ptr is a pointer to kvfree(), @rhf is the name
- * of the rcu_head structure within the type of @ptr.
+ * kfree_rcu_mightsleep() - kfree an object after a grace period.
+ * @ptr: pointer to kfree for single-argument invocations.
*
* When it comes to head-less variant, only one argument
* is passed and that is just a pointer which has to be
* freed after a grace period. Therefore the semantic is
*
- * kvfree_rcu(ptr);
+ * kfree_rcu_mightsleep(ptr);
*
* where @ptr is the pointer to be freed by kvfree().
*
@@ -1012,13 +1003,9 @@ static inline notrace void rcu_read_unlock_sched_notrace(void)
* annotation. Otherwise, please switch and embed the
* rcu_head structure within the type of @ptr.
*/
-#define kvfree_rcu(...) KVFREE_GET_MACRO(__VA_ARGS__, \
- kvfree_rcu_arg_2, kvfree_rcu_arg_1)(__VA_ARGS__)
-
+#define kfree_rcu_mightsleep(ptr) kvfree_rcu_arg_1(ptr)
#define kvfree_rcu_mightsleep(ptr) kvfree_rcu_arg_1(ptr)
-#define kfree_rcu_mightsleep(ptr) kvfree_rcu_mightsleep(ptr)
-#define KVFREE_GET_MACRO(_1, _2, NAME, ...) NAME
#define kvfree_rcu_arg_2(ptr, rhf) \
do { \
typeof (ptr) ___p = (ptr); \
--
2.40.1
next prev parent reply other threads:[~2023-05-10 17:03 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-10 17:02 [PATCH rcu 0/8] kvfree_rcu() changes for v6.5 Paul E. McKenney
2023-05-10 17:02 ` Paul E. McKenney [this message]
2023-05-10 17:02 ` [PATCH rcu 2/8] rcu/kvfree: Add debug to check grace periods Paul E. McKenney
2023-05-10 17:02 ` [PATCH rcu 3/8] rcu/kvfree: Add debug check for GP complete for kfree_rcu_cpu list Paul E. McKenney
2023-05-10 17:02 ` [PATCH rcu 4/8] rcu/kvfree: Invoke debug_rcu_bhead_unqueue() after checking bnode->gp_snap Paul E. McKenney
2023-05-10 17:02 ` [PATCH rcu 5/8] rcu/kvfree: Use consistent krcp when growing kfree_rcu() page cache Paul E. McKenney
2023-05-10 17:02 ` [PATCH rcu 6/8] rcu/kvfree: Do not run a page work if a cache is disabled Paul E. McKenney
2023-05-10 17:02 ` [PATCH rcu 7/8] rcu/kvfree: Make fill page cache start from krcp->nr_bkv_objs Paul E. McKenney
2023-05-10 17:02 ` [PATCH rcu 8/8] rcu/kvfree: Make drain_page_cache() take early return if cache is disabled Paul E. McKenney
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