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author | Lai Jiangshan <laijs@cn.fujitsu.com> | 2012-11-29 12:46:07 +0400 |
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committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2013-02-08 03:17:01 +0400 |
commit | 34a64b6bb64b5cf193932e2b4394c5284732e008 (patch) | |
tree | 9a83d6cb769c4c21364f0ba0161ebd76ed03b512 /kernel/srcu.c | |
parent | 511a0868bed6694512348fc177cdfaf3fd97d0bb (diff) | |
download | linux-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.c | 10 |
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. |