From: David Vernet Date: Tue, 29 Mar 2022 22:26:13 +0000 (-0700) Subject: rcu_sync: Fix comment to properly reflect rcu_sync_exit() behavior X-Git-Tag: v5.19-rc1~252^2~1^2~1 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=f1efe84d6fd2af163989025bc285ff9b3b0c764f;p=thirdparty%2Flinux.git 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 Signed-off-by: Paul E. McKenney --- diff --git a/kernel/rcu/sync.c b/kernel/rcu/sync.c index 33d896d859023..5cefc702158fe 100644 --- a/kernel/rcu/sync.c +++ b/kernel/rcu/sync.c @@ -111,7 +111,7 @@ static void rcu_sync_func(struct rcu_head *rhp) * a slowpath during the update. After this function returns, all * subsequent calls to rcu_sync_is_idle() will return false, which * 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 * period, however, closely spaced calls to rcu_sync_enter() can