USB: serial: relax unthrottle memory barrier (32553441) · Commits · 戴 / test

Commit ("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>

drivers/usb/serial/generic.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -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);
		}

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