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authorOleg Nesterov <oleg@redhat.com>2014-07-08 15:17:59 -0700
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2014-09-07 16:18:13 -0700
commit85b39d305bfe809a11ff2770d380be3e2465beec (patch)
tree2bc6f52c07779203329b0d791f631ab894a8846e /kernel/rcu/update.c
parente02b2edfa13878c6671d31d5c736f56f89d99bf1 (diff)
downloadlinux-sh-85b39d305bfe809a11ff2770d380be3e2465beec.tar.gz
rcu: Uninline rcu_read_lock_held()
This commit uninlines rcu_read_lock_held(). According to "size vmlinux" this saves 28549 in .text: - 5541731 3014560 14757888 23314179 + 5513182 3026848 14757888 23297918 Note: it looks as if the data grows by 12288 bytes but this is not true, it does not actually grow. But .data starts with ALIGN(THREAD_SIZE) and since .text shrinks the padding grows, and thus .data grows too as it seen by /bin/size. diff System.map: - ffffffff81510000 D _sdata - ffffffff81510000 D init_thread_union + ffffffff81509000 D _sdata + ffffffff8150c000 D init_thread_union Perhaps we can change vmlinux.lds.S to .data itself, so that /bin/size can't "wrongly" report that .data grows if .text shinks. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'kernel/rcu/update.c')
-rw-r--r--kernel/rcu/update.c32
1 files changed, 32 insertions, 0 deletions
diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
index 4056d7992a6c..ea8ea7b16e11 100644
--- a/kernel/rcu/update.c
+++ b/kernel/rcu/update.c
@@ -137,6 +137,38 @@ int notrace debug_lockdep_rcu_enabled(void)
EXPORT_SYMBOL_GPL(debug_lockdep_rcu_enabled);
/**
+ * rcu_read_lock_held() - might we be in RCU read-side critical section?
+ *
+ * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an RCU
+ * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC,
+ * this assumes we are in an RCU read-side critical section unless it can
+ * prove otherwise. This is useful for debug checks in functions that
+ * require that they be called within an RCU read-side critical section.
+ *
+ * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot
+ * and while lockdep is disabled.
+ *
+ * Note that rcu_read_lock() and the matching rcu_read_unlock() must
+ * occur in the same context, for example, it is illegal to invoke
+ * rcu_read_unlock() in process context if the matching rcu_read_lock()
+ * was invoked from within an irq handler.
+ *
+ * Note that rcu_read_lock() is disallowed if the CPU is either idle or
+ * offline from an RCU perspective, so check for those as well.
+ */
+int rcu_read_lock_held(void)
+{
+ if (!debug_lockdep_rcu_enabled())
+ return 1;
+ if (!rcu_is_watching())
+ return 0;
+ if (!rcu_lockdep_current_cpu_online())
+ return 0;
+ return lock_is_held(&rcu_lock_map);
+}
+EXPORT_SYMBOL_GPL(rcu_read_lock_held);
+
+/**
* rcu_read_lock_bh_held() - might we be in RCU-bh read-side critical section?
*
* Check for bottom half being disabled, which covers both the