From: Johan Hovold <johan@kernel.org>
To: Johan Hovold <johan@kernel.org>
Cc: linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
Davidlohr Bueso <dave@stgolabs.net>
Subject: [PATCH] USB: serial: relax unthrottle memory barrier
Date: Thu, 30 Jan 2020 11:06:58 +0100 [thread overview]
Message-ID: <20200130100658.683-1-johan@kernel.org> (raw)
Commit a8d78d9f3856 ("USB: serial: clean up throttle handling")
converted the throttle handling to use atomic bitops. This means that we
can relax the smp_mb() in unthrottle() to smp_mb__after_atomic(), which
for example is a no-op on architectures like x86 that provide fully
ordered atomics.
Signed-off-by: Johan Hovold <johan@kernel.org>
---
drivers/usb/serial/generic.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/usb/serial/generic.c b/drivers/usb/serial/generic.c
index 1be8bea372a2..546a1c2ce2f2 100644
--- a/drivers/usb/serial/generic.c
+++ b/drivers/usb/serial/generic.c
@@ -417,7 +417,7 @@ void usb_serial_generic_read_bulk_callback(struct urb *urb)
/*
* Make sure URB is marked as free before checking the throttled flag
* to avoid racing with unthrottle() on another CPU. Matches the
- * smp_mb() in unthrottle().
+ * smp_mb__after_atomic() in unthrottle().
*/
smp_mb__after_atomic();
@@ -489,7 +489,7 @@ void usb_serial_generic_unthrottle(struct tty_struct *tty)
* Matches the smp_mb__after_atomic() in
* usb_serial_generic_read_bulk_callback().
*/
- smp_mb();
+ smp_mb__after_atomic();
usb_serial_generic_submit_read_urbs(port, GFP_KERNEL);
}
--
2.24.1
next reply other threads:[~2020-01-30 10:08 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-30 10:06 Johan Hovold [this message]
2020-01-30 10:23 ` [PATCH] USB: serial: relax unthrottle memory barrier Greg KH
2020-01-30 15:33 ` Davidlohr Bueso
2020-02-10 9:38 ` Johan Hovold
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