linux-kernel - Re: [PATCH 7/8] usb, cdc-acm: optimize barrier usage for Rmw atomic bitops

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Message-ID: <20200323172954.pyxw5v4pmuvkbjrp@linux-p48b>
Date:   Mon, 23 Mar 2020 10:29:54 -0700
From:   Davidlohr Bueso <dave@...olabs.net>
To:     oneukum@...e.com
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        Davidlohr Bueso <dbueso@...e.de>
Subject: Re: [PATCH 7/8] usb, cdc-acm: optimize barrier usage for Rmw atomic
 bitops

ping? Can these please be picked up?

On Wed, 29 Jan 2020, Davidlohr Bueso wrote:

>We can avoid the unnecessary barrier on non LL/SC architectures,
>such as x86. Instead, use the smp_mb__after_atomic() call.
>
>Signed-off-by: Davidlohr Bueso <dbueso@...e.de>
>---
> drivers/usb/class/cdc-acm.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
>diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
>index 62f4fb9b362f..0bc4b558f387 100644
>--- a/drivers/usb/class/cdc-acm.c
>+++ b/drivers/usb/class/cdc-acm.c
>@@ -842,7 +842,7 @@ static void acm_tty_unthrottle(struct tty_struct *tty)
> 	clear_bit(ACM_THROTTLED, &acm->flags);
>
> 	/* Matches the smp_mb__after_atomic() in acm_read_bulk_callback(). */
>-	smp_mb();
>+	smp_mb__after_atomic();
>
> 	acm_submit_read_urbs(acm, GFP_KERNEL);
> }
>-- 
>2.16.4
>