Revision c4e18497d8fd92eef2c6e7eadcc1a107ccd115ea authored by Guenter Roeck on 20 December 2012, 23:05:42 UTC, committed by Linus Torvalds on 21 December 2012, 01:40:20 UTC
Commit 263a523d18bc ("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>
1 parent 154b454
crypto_wq.c
/*
* Workqueue for crypto subsystem
*
* Copyright (c) 2009 Intel Corp.
* Author: Huang Ying <ying.huang@intel.com>
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the Free
* Software Foundation; either version 2 of the License, or (at your option)
* any later version.
*
*/
#include <linux/workqueue.h>
#include <linux/module.h>
#include <crypto/algapi.h>
#include <crypto/crypto_wq.h>
struct workqueue_struct *kcrypto_wq;
EXPORT_SYMBOL_GPL(kcrypto_wq);
static int __init crypto_wq_init(void)
{
kcrypto_wq = alloc_workqueue("crypto",
WQ_MEM_RECLAIM | WQ_CPU_INTENSIVE, 1);
if (unlikely(!kcrypto_wq))
return -ENOMEM;
return 0;
}
static void __exit crypto_wq_exit(void)
{
destroy_workqueue(kcrypto_wq);
}
module_init(crypto_wq_init);
module_exit(crypto_wq_exit);
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Workqueue for crypto subsystem");
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