Guenter Roeck c4e18497d8 linux/kernel.h: fix DIV_ROUND_CLOSEST with unsigned divisors ... Commit 263a523d18 ("linux/kernel.h: Fix warning seen with W=1 due to change in DIV_ROUND_CLOSEST") fixes a warning seen with W=1 due to change in DIV_ROUND_CLOSEST. Unfortunately, the C compiler converts divide operations with unsigned divisors to unsigned, even if the dividend is signed and negative (for example, -10 / 5U = 858993457). The C standard says "If one operand has unsigned int type, the other operand is converted to unsigned int", so the compiler is not to blame. As a result, DIV_ROUND_CLOSEST(0, 2U) and similar operations now return bad values, since the automatic conversion of expressions such as "0 - 2U/2" to unsigned was not taken into account. Fix by checking for the divisor variable type when deciding which operation to perform. This fixes DIV_ROUND_CLOSEST(0, 2U), but still returns bad values for negative dividends divided by unsigned divisors. Mark the latter case as unsupported. One observed effect of this problem is that the s2c_hwmon driver reports a value of 4198403 instead of 0 if the ADC reads 0. Other impact is unpredictable. Problem is seen if the divisor is an unsigned variable or constant and the dividend is less than (divisor/2). Signed-off-by: Guenter Roeck <linux@roeck-us.net> Reported-by: Juergen Beisert <jbe@pengutronix.de> Tested-by: Juergen Beisert <jbe@pengutronix.de> Cc: Jean Delvare <khali@linux-fr.org> Cc: <stable@vger.kernel.org> [3.7.x] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>		2012-12-20 17:40:20 -08:00
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acpi	PCI changes for the v3.8 merge window:	2012-12-13 12:14:47 -08:00
asm-generic	asm-generic: io: don't perform swab during {in,out} string functions	2012-12-17 17:15:13 -08:00
clocksource
crypto
drm	Merge branch 'drm-intel-fixes' of git://people.freedesktop.org/~danvet/drm-intel into drm-next	2012-12-16 06:05:03 +00:00
keys
linux	linux/kernel.h: fix DIV_ROUND_CLOSEST with unsigned divisors	2012-12-20 17:40:20 -08:00
math-emu
media
memory
misc
net	Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net	2012-12-19 20:29:15 -08:00
pcmcia
ras
rdma
rxrpc
scsi	SCSI misc on 20121212	2012-12-13 19:20:31 -08:00
sound	ASoC: More updates for v3.8	2012-12-17 15:40:55 +01:00
target	target/iscsi_target: Add NodeACL tags for initiator group support	2012-12-13 14:18:09 -08:00
trace	mm: add a __GFP_KMEMCG flag	2012-12-18 15:02:12 -08:00
uapi	Some nice cleanups, and even a patch my wife did as a "live" demo for	2012-12-20 08:37:05 -08:00
video	Merge branch 'omap-for-v3.8/fixes-for-merge-window' into omap-for-v3.8/fixes-for-merge-window-v2	2012-12-16 11:28:10 -08:00
xen	Bugfixes:	2012-12-18 12:26:54 -08:00
Kbuild