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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>
This commit is contained in:
Lai Jiangshan 2012-11-29 16:46:07 +08:00 committed by Paul E. McKenney
parent 511a0868be
commit 34a64b6bb6
1 changed files with 6 additions and 4 deletions
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10
kernel/srcu.c
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@ -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.