From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: linux-kernel@vger.kernel.org
Cc: mingo@elte.hu, laijs@cn.fujitsu.com, dipankar@in.ibm.com,
akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca,
josh@joshtriplett.org, niv@us.ibm.com, tglx@linutronix.de,
peterz@infradead.org, rostedt@goodmis.org,
Valdis.Kletnieks@vt.edu, dhowells@redhat.com,
eric.dumazet@gmail.com, darren@dvhart.com, fweisbec@gmail.com,
patches@linaro.org, Jan Engelhardt <jengelh@medozas.de>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: [PATCH RFC tip/core/rcu 5/6] rcu: Make __kfree_rcu() less dependent on compiler choices
Date: Mon, 23 Apr 2012 09:42:26 -0700 [thread overview]
Message-ID: <1335199347-13926-5-git-send-email-paulmck@linux.vnet.ibm.com> (raw)
In-Reply-To: <1335199347-13926-1-git-send-email-paulmck@linux.vnet.ibm.com>
From: Jan Engelhardt <jengelh@medozas.de>
Currently, __kfree_rcu() is implemented as an inline function, and
contains a BUILD_BUG_ON() that malfunctions if __kfree_rcu() is compiled
as an out-of-line function. Unfortunately, there are compiler settings
(e.g., -O0) that can result in __kfree_rcu() being compiled out of line,
resulting in annoying build breakage. This commit therefore converts
both __kfree_rcu() and __is_kfree_rcu_offset() from inline functions to
macros to prevent such misbehavior on the part of the compiler.
Signed-off-by: Jan Engelhardt <jengelh@medozas.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
---
include/linux/rcupdate.h | 18 ++++++++++++++++++
1 files changed, 18 insertions(+), 0 deletions(-)
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 20fb776..d5dfb10 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -922,6 +922,21 @@ void __kfree_rcu(struct rcu_head *head, unsigned long offset)
kfree_call_rcu(head, (rcu_callback)offset);
}
+/*
+ * Does the specified offset indicate that the corresponding rcu_head
+ * structure can be handled by kfree_rcu()?
+ */
+#define __is_kfree_rcu_offset(offset) ((offset) < 4096)
+
+/*
+ * Helper macro for kfree_rcu() to prevent argument-expansion eyestrain.
+ */
+#define __kfree_rcu(head, offset) \
+ do { \
+ BUILD_BUG_ON(!__is_kfree_rcu_offset(offset)); \
+ call_rcu(head, (void (*)(struct rcu_head *))(unsigned long)(offset)); \
+ } while (0)
+
/**
* kfree_rcu() - kfree an object after a grace period.
* @ptr: pointer to kfree
@@ -944,6 +959,9 @@ void __kfree_rcu(struct rcu_head *head, unsigned long offset)
*
* Note that the allowable offset might decrease in the future, for example,
* to allow something like kmem_cache_free_rcu().
+ *
+ * The BUILD_BUG_ON check must not involve any function calls, hence the
+ * checks are done in macros here.
*/
#define kfree_rcu(ptr, rcu_head) \
__kfree_rcu(&((ptr)->rcu_head), offsetof(typeof(*(ptr)), rcu_head))
--
1.7.8
next prev parent reply other threads:[~2012-04-23 16:44 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-23 16:41 [PATCH RFC 0/6] Miscellaneous RCU fixes for 3.5 Paul E. McKenney
2012-04-23 16:42 ` [PATCH RFC tip/core/rcu 1/6] rcu: Stabilize use of num_online_cpus() for GP short circuit Paul E. McKenney
2012-04-23 16:42 ` [PATCH RFC tip/core/rcu 2/6] rcu: List-debug variants of rcu list routines Paul E. McKenney
2012-04-23 16:42 ` [PATCH RFC tip/core/rcu 3/6] rcu: Replace list_first_entry_rcu() with list_first_or_null_rcu() Paul E. McKenney
2012-04-23 16:42 ` [PATCH RFC tip/core/rcu 4/6] rcu: Clarify help text for RCU_BOOST_PRIO Paul E. McKenney
2012-04-26 12:46 ` Peter Zijlstra
2012-04-26 17:28 ` Paul E. McKenney
2012-04-23 16:42 ` Paul E. McKenney [this message]
2012-04-26 12:48 ` [PATCH RFC tip/core/rcu 5/6] rcu: Make __kfree_rcu() less dependent on compiler choices Peter Zijlstra
2012-04-26 13:29 ` Jan Engelhardt
2012-04-26 13:50 ` Peter Zijlstra
2012-04-23 16:42 ` [PATCH RFC tip/core/rcu 6/6] rcu: Reduce cache-miss initialization latencies for large systems Paul E. McKenney
2012-04-26 12:51 ` Peter Zijlstra
2012-04-26 14:12 ` Paul E. McKenney
2012-04-26 15:28 ` Peter Zijlstra
2012-04-26 16:15 ` Paul E. McKenney
2012-04-26 19:41 ` Peter Zijlstra
2012-04-26 19:47 ` Peter Zijlstra
2012-04-26 20:29 ` Paul E. McKenney
2012-04-26 22:04 ` Peter Zijlstra
2012-04-26 20:28 ` Paul E. McKenney
2012-04-26 22:01 ` Peter Zijlstra
2012-04-27 14:17 ` Paul E. McKenney
2012-04-27 4:36 ` Mike Galbraith
2012-04-27 15:15 ` Paul E. McKenney
2012-04-28 4:42 ` Mike Galbraith
2012-04-28 17:21 ` Paul E. McKenney
2012-04-29 3:54 ` Mike Galbraith
2012-04-24 15:35 ` [PATCH RFC tip/core/rcu 1/6] rcu: Stabilize use of num_online_cpus() for GP short circuit Srivatsa S. Bhat
2012-04-24 16:50 ` Paul E. McKenney
2012-04-24 17:46 ` Srivatsa S. Bhat
2012-05-07 3:47 ` Rusty Russell
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