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authorJohan Hovold <jhovold@gmail.com>2013-11-09 12:38:09 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-01-08 09:42:10 -0800
commitbc845e5405b033fadd398c5ca2884a568313c875 (patch)
treea9cbbab5a9f102c45cb85d2b18b7c9202378fe73
parent84dfcb758ba7cce52ef475ac96861a558e1a20ca (diff)
downloadlinux-linaro-stable-bc845e5405b033fadd398c5ca2884a568313c875.tar.gz
USB: serial: fix race in generic write
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@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--drivers/usb/serial/generic.c9
1 files changed, 1 insertions, 8 deletions
diff --git a/drivers/usb/serial/generic.c b/drivers/usb/serial/generic.c
index 664deb63807c..546177fa7cfe 100644
--- a/drivers/usb/serial/generic.c
+++ b/drivers/usb/serial/generic.c
@@ -223,14 +223,7 @@ 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 */
}
/**