From: Andreas Schwab <schwab@linux-m68k.org>
To: Joe Perches <joe@perches.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>,
Karsten Keil <isdn@linux-pingi.de>,
"David S. Miller" <davem@davemloft.net>,
Masanari Iida <standby24x7@gmail.com>,
netdev@vger.kernel.org, kernel-janitors@vger.kernel.org
Subject: Re: [patch] isdn: fix a wrapping bug in isdn_ppp_ioctl()
Date: Wed, 10 Oct 2012 13:58:38 +0000 [thread overview]
Message-ID: <m2sj9m5sz5.fsf@igel.home> (raw)
In-Reply-To: <1349874007.2386.42.camel@joe-AO722> (Joe Perches's message of "Wed, 10 Oct 2012 06:00:07 -0700")
Sorry, I was misremembering the history of the bit ops. There has
historically been issues with varying bit order, but noadays set_bit is
always defined consistently with C shifts.
But another issue, set_bit is an atomic operation which may be
significantly more expensive than the equivalent C operation. Better
use __set_bit when atomicity is not needed.
Andreas.
--
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756 01D3 44D5 214B 8276 4ED5
"And now for something completely different."
WARNING: multiple messages have this Message-ID (diff)
From: Andreas Schwab <schwab@linux-m68k.org>
To: Joe Perches <joe@perches.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>,
Karsten Keil <isdn@linux-pingi.de>,
"David S. Miller" <davem@davemloft.net>,
Masanari Iida <standby24x7@gmail.com>,
netdev@vger.kernel.org, kernel-janitors@vger.kernel.org
Subject: Re: [patch] isdn: fix a wrapping bug in isdn_ppp_ioctl()
Date: Wed, 10 Oct 2012 15:58:38 +0200 [thread overview]
Message-ID: <m2sj9m5sz5.fsf@igel.home> (raw)
In-Reply-To: <1349874007.2386.42.camel@joe-AO722> (Joe Perches's message of "Wed, 10 Oct 2012 06:00:07 -0700")
Sorry, I was misremembering the history of the bit ops. There has
historically been issues with varying bit order, but noadays set_bit is
always defined consistently with C shifts.
But another issue, set_bit is an atomic operation which may be
significantly more expensive than the equivalent C operation. Better
use __set_bit when atomicity is not needed.
Andreas.
--
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756 01D3 44D5 214B 8276 4ED5
"And now for something completely different."
next prev parent reply other threads:[~2012-10-10 13:58 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-10 9:42 [patch] isdn: fix a wrapping bug in isdn_ppp_ioctl() Dan Carpenter
2012-10-10 9:42 ` Dan Carpenter
2012-10-10 10:19 ` Joe Perches
2012-10-10 10:19 ` Joe Perches
2012-10-10 10:41 ` Joe Perches
2012-10-10 10:41 ` Joe Perches
2012-10-10 10:42 ` David Laight
2012-10-10 10:42 ` David Laight
2012-10-10 11:15 ` Joe Perches
2012-10-10 11:15 ` Joe Perches
2012-10-10 12:05 ` Andreas Schwab
2012-10-10 12:05 ` Andreas Schwab
2012-10-10 13:00 ` Joe Perches
2012-10-10 13:00 ` Joe Perches
2012-10-10 13:58 ` Andreas Schwab [this message]
2012-10-10 13:58 ` Andreas Schwab
2012-10-10 14:41 ` Joe Perches
2012-10-10 14:41 ` Joe Perches
2012-10-10 14:59 ` David Laight
2012-10-10 14:59 ` David Laight
2012-10-10 15:19 ` Joe Perches
2012-10-10 15:19 ` Joe Perches
2012-10-10 15:44 ` David Laight
2012-10-10 15:44 ` David Laight
2012-10-10 15:52 ` Joe Perches
2012-10-10 15:52 ` Joe Perches
2012-10-12 7:49 ` Karsten Keil
2012-10-12 7:49 ` Karsten Keil
2012-10-11 2:46 ` David Miller
2012-10-11 2:46 ` David Miller
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