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USB: serial: relax unthrottle memory barrier

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Commit a8d78d9f38 ("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.

Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Johan Hovold <johan@kernel.org>
This commit is contained in:
Johan Hovold 2020-01-30 11:06:58 +01:00
parent bb6d3fb354
commit 3255344156
1 changed files with 2 additions and 2 deletions
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4
drivers/usb/serial/generic.c
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@ -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);
}