linux-kernel - [56/59] USB: xhci: Remove buggy assignment in next

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Message-Id: <20100824222527.286994497@clark.site>
Date:	Tue, 24 Aug 2010 15:25:08 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	John Youn <johnyoun@...opsys.com>,
	Sarah Sharp <sarah.a.sharp@...ux.intel.com>
Subject: [56/59] USB: xhci: Remove buggy assignment in next_trb()

2.6.32-stable review patch.  If anyone has any objections, please let us know.

------------------

From: John Youn <John.Youn@...opsys.com>

commit a1669b2c64a9c8b031e0ac5cbf2692337a577f7c upstream.

The code to increment the TRB pointer has a slight ambiguity that could
lead to a bug on different compilers.  The ANSI C specification does not
specify the precedence of the assignment operator over the postfix
operator.  gcc 4.4 produced the correct code (increment the pointer and
assign the value), but a MIPS compiler that one of John's clients used
assigned the old (unincremented) value.

Remove the unnecessary assignment to make all compilers produce the
correct assembly.

Signed-off-by: John Youn <johnyoun@...opsys.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@...ux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 drivers/usb/host/xhci-ring.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -124,7 +124,7 @@ static void next_trb(struct xhci_hcd *xh
 		*seg = (*seg)->next;
 		*trb = ((*seg)->trbs);
 	} else {
-		*trb = (*trb)++;
+		(*trb)++;
 	}
 }

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