OrgACRN
/
acrn-kernel
mirror of https://github.com/projectacrn/acrn-kernel.git
1
0
Fork 0
Code Issues Releases Wiki Activity

rcu_sync: Fix comment to properly reflect rcu_sync_exit() behavior 

The rcu_sync_enter() function is used by updaters to force RCU readers
(e.g. percpu-rwsem) to use their slow paths during an update.  This is
accomplished by setting the ->gp_state of the rcu_sync structure to
GP_ENTER.  In the case of percpu-rwsem, the readers' slow path waits on
a semaphore instead of just incrementing a reader count.  Each updater
invokes the rcu_sync_exit() function to signal to readers that they
may again take their fastpaths.  The rcu_sync_exit() function sets the
->gp_state of the rcu_sync structure to GP_EXIT, and if all goes well,
after a grace period the ->gp_state reverts back to GP_IDLE.

Unfortunately, the rcu_sync_enter() function currently has a comment
incorrectly stating that rcu_sync_exit() (by an updater) will re-enable
reader "slowpaths".  This patch changes the comment to state that this
function re-enables reader fastpaths.

Signed-off-by: David Vernet <void@manifault.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
David Vernet 2022-03-29 15:26:13 -07:00 committed by Paul E. McKenney
parent 88ca472f80
commit f1efe84d6f
1 changed files with 1 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
kernel/rcu/sync.c
View File

@ -111,7 +111,7 @@ static void rcu_sync_func(struct rcu_head *rhp)
* a slowpath during the update. After this function returns, all * a slowpath during the update. After this function returns, all
* subsequent calls to rcu_sync_is_idle() will return false, which * subsequent calls to rcu_sync_is_idle() will return false, which
* tells readers to stay off their fastpaths. A later call to * tells readers to stay off their fastpaths. A later call to
* rcu_sync_exit() re-enables reader slowpaths. * rcu_sync_exit() re-enables reader fastpaths.
* *
* When called in isolation, rcu_sync_enter() must wait for a grace * When called in isolation, rcu_sync_enter() must wait for a grace
* period, however, closely spaced calls to rcu_sync_enter() can * period, however, closely spaced calls to rcu_sync_enter() can