From 6f6485463aada1ec6a0f3db6a03eb8e393d6bb55 Mon Sep 17 00:00:00 2001 From: Johan Hovold Date: Sat, 9 Nov 2013 12:38:09 +0100 Subject: [PATCH] USB: serial: fix race in generic write Fix race in generic write implementation, which could lead to temporarily degraded throughput. The current generic write implementation introduced by commit 27c7acf22047 ("USB: serial: reimplement generic fifo-based writes") has always had this bug, although it's fairly hard to trigger and the consequences are not likely to be noticed. Specifically, a write() on one CPU while the completion handler is running on another could result in only one of the two write urbs being utilised to empty the remainder of the write fifo (unless there is a second write() that doesn't race during that time). Cc: stable # 2.6.35 Signed-off-by: Johan Hovold Signed-off-by: Greg Kroah-Hartman --- drivers/usb/serial/generic.c | 10 +--------- 1 file changed, 1 insertion(+), 9 deletions(-) diff --git a/drivers/usb/serial/generic.c b/drivers/usb/serial/generic.c index 2b01ec8..e36b25a 100644 --- a/drivers/usb/serial/generic.c +++ b/drivers/usb/serial/generic.c @@ -173,16 +173,8 @@ retry: clear_bit_unlock(USB_SERIAL_WRITE_BUSY, &port->flags); return result; } - /* - * Try sending off another urb, unless called from completion handler - * (in which case there will be no free urb or no data). - */ - if (mem_flags != GFP_ATOMIC) - goto retry; - clear_bit_unlock(USB_SERIAL_WRITE_BUSY, &port->flags); - - return 0; + goto retry; /* try sending off another urb */ } EXPORT_SYMBOL_GPL(usb_serial_generic_write_start); -- 2.7.4