linux-kernel - Re: [PATCH] rcu_sync: Fix comment to properly reflect rcu_sync

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Message-ID: <20220329193613.2a3g3bkxadocirgm@user-VirtualBox>
Date:   Tue, 29 Mar 2022 15:36:13 -0400
From:   David Vernet <void@...ifault.com>
To:     "Paul E. McKenney" <paulmck@...nel.org>
Cc:     frederic@...nel.org, jiangshanlai@...il.com,
        joel@...lfernandes.org, josh@...htriplett.org,
        linux-kernel@...r.kernel.org, mathieu.desnoyers@...icios.com,
        quic_neeraju@...cinc.com, rcu@...r.kernel.org, rostedt@...dmis.org
Subject: Re: [PATCH] rcu_sync: Fix comment to properly reflect
 rcu_sync_exit() behavior

On Tue, Mar 29, 2022 at 04:22:56PM -0700, Paul E. McKenney wrote:
> As usual, I could not resist the urge to wordsmith.  Please take a look
> at the following to see if I messed something up.
> 
> 							Thanx, Paul
> 
> ------------------------------------------------------------------------
> 
> commit b89e06a95c05009bcf31949814c42bc420f414a6
> Author: David Vernet <void@...ifault.com>
> Date:   Tue Mar 29 15:26:13 2022 -0700
> 
>     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@...ifault.com>
>     Signed-off-by: Paul E. McKenney <paulmck@...nel.org>

The word smithing looks like a good improvement to me!

Thanks,
David