This is a note to let you know that I've just added the patch titled
USB: serial: fix race in generic write
to the 3.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
usb-serial-fix-race-in-generic-write.patch
and it can be found in the queue-3.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 6f6485463aada1ec6a0f3db6a03eb8e393d6bb55 Mon Sep 17 00:00:00 2001
From: Johan Hovold <jhovold@xxxxxxxxx>
Date: Sat, 9 Nov 2013 12:38:09 +0100
Subject: USB: serial: fix race in generic write
From: Johan Hovold <jhovold@xxxxxxxxx>
commit 6f6485463aada1ec6a0f3db6a03eb8e393d6bb55 upstream.
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).
Signed-off-by: Johan Hovold <jhovold@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/usb/serial/generic.c | 9 +--------
1 file changed, 1 insertion(+), 8 deletions(-)
--- a/drivers/usb/serial/generic.c
+++ b/drivers/usb/serial/generic.c
@@ -176,14 +176,7 @@ retry:
return result;
}
- /* Try sending off another urb, unless in irq context (in which case
- * there will be no free urb). */
- if (!in_irq())
- goto retry;
-
- clear_bit_unlock(USB_SERIAL_WRITE_BUSY, &port->flags);
-
- return 0;
+ goto retry; /* try sending off another urb */
}
/**
Patches currently in stable-queue which might be from jhovold@xxxxxxxxx are
queue-3.10/usb-serial-fix-race-in-generic-write.patch
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