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authorLai Jiangshan <laijs@cn.fujitsu.com>2012-11-29 12:46:07 +0400
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2013-02-08 03:17:01 +0400
commit34a64b6bb64b5cf193932e2b4394c5284732e008 (patch)
tree9a83d6cb769c4c21364f0ba0161ebd76ed03b512 /kernel/srcu.c
parent511a0868bed6694512348fc177cdfaf3fd97d0bb (diff)
downloadlinux-34a64b6bb64b5cf193932e2b4394c5284732e008.tar.xz
srcu: Update synchronize_srcu()'s comments
The core of SRCU is changed, but synchronize_srcu()'s comments describe the old algorithm. This commit therefore updates them to match the new algorithm. Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'kernel/srcu.c')
-rw-r--r--kernel/srcu.c10
1 files changed, 6 insertions, 4 deletions
diff --git a/kernel/srcu.c b/kernel/srcu.c
index 7cf5baba96f9..f098f1768215 100644
--- a/kernel/srcu.c
+++ b/kernel/srcu.c
@@ -450,10 +450,12 @@ static void __synchronize_srcu(struct srcu_struct *sp, int trycount)
* synchronize_srcu - wait for prior SRCU read-side critical-section completion
* @sp: srcu_struct with which to synchronize.
*
- * Flip the completed counter, and wait for the old count to drain to zero.
- * As with classic RCU, the updater must use some separate means of
- * synchronizing concurrent updates. Can block; must be called from
- * process context.
+ * Wait for the count to drain to zero of both indexes. To avoid the
+ * possible starvation of synchronize_srcu(), it waits for the count of
+ * the index=((->completed & 1) ^ 1) to drain to zero at first,
+ * and then flip the completed and wait for the count of the other index.
+ *
+ * Can block; must be called from process context.
*
* Note that it is illegal to call synchronize_srcu() from the corresponding
* SRCU read-side critical section; doing so will result in deadlock.