From: Ingo Molnar <mingo@elte.hu>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org,
Thomas Gleixner <tglx@linutronix.de>,
"H. Peter Anvin" <hpa@zytor.com>
Subject: [GIT PULL] x86 fix
Date: Mon, 10 Aug 2009 20:08:09 +0200 [thread overview]
Message-ID: <20090810180809.GA26073@elte.hu> (raw)
Linus,
Please pull the latest x86-fixes-for-linus git tree from:
git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip.git x86-fixes-for-linus
Thanks,
Ingo
------------------>
Linus Torvalds (1):
x86: Fix serialization in pit_expect_msb()
arch/x86/kernel/tsc.c | 29 ++++++++++++++++++++++-------
1 files changed, 22 insertions(+), 7 deletions(-)
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 6e1a368..71f4368 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -275,15 +275,20 @@ static unsigned long pit_calibrate_tsc(u32 latch, unsigned long ms, int loopmin)
* use the TSC value at the transitions to calculate a pretty
* good value for the TSC frequencty.
*/
+static inline int pit_verify_msb(unsigned char val)
+{
+ /* Ignore LSB */
+ inb(0x42);
+ return inb(0x42) == val;
+}
+
static inline int pit_expect_msb(unsigned char val, u64 *tscp, unsigned long *deltap)
{
int count;
u64 tsc = 0;
for (count = 0; count < 50000; count++) {
- /* Ignore LSB */
- inb(0x42);
- if (inb(0x42) != val)
+ if (!pit_verify_msb(val))
break;
tsc = get_cycles();
}
@@ -336,8 +341,7 @@ static unsigned long quick_pit_calibrate(void)
* to do that is to just read back the 16-bit counter
* once from the PIT.
*/
- inb(0x42);
- inb(0x42);
+ pit_verify_msb(0);
if (pit_expect_msb(0xff, &tsc, &d1)) {
for (i = 1; i <= MAX_QUICK_PIT_ITERATIONS; i++) {
@@ -348,8 +352,19 @@ static unsigned long quick_pit_calibrate(void)
* Iterate until the error is less than 500 ppm
*/
delta -= tsc;
- if (d1+d2 < delta >> 11)
- goto success;
+ if (d1+d2 >= delta >> 11)
+ continue;
+
+ /*
+ * Check the PIT one more time to verify that
+ * all TSC reads were stable wrt the PIT.
+ *
+ * This also guarantees serialization of the
+ * last cycle read ('d2') in pit_expect_msb.
+ */
+ if (!pit_verify_msb(0xfe - i))
+ break;
+ goto success;
}
}
printk("Fast TSC calibration failed\n");
next reply other threads:[~2009-08-10 18:08 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-08-10 18:08 Ingo Molnar [this message]
-- strict thread matches above, loose matches on Subject: below --
2023-09-02 10:24 [GIT PULL] x86 fix Ingo Molnar
2023-09-02 16:13 ` pr-tracker-bot
2022-08-13 10:40 Ingo Molnar
2022-08-13 21:48 ` pr-tracker-bot
2020-08-02 19:17 Ingo Molnar
2020-08-02 20:15 ` pr-tracker-bot
2020-04-02 9:51 Ingo Molnar
2020-04-02 22:00 ` Linus Torvalds
2020-04-02 22:45 ` pr-tracker-bot
2020-03-24 9:06 Ingo Molnar
2020-03-24 17:15 ` pr-tracker-bot
2019-12-17 11:58 Ingo Molnar
2019-12-17 19:20 ` pr-tracker-bot
2019-09-28 12:42 Ingo Molnar
2019-09-28 20:50 ` pr-tracker-bot
2019-07-14 11:32 Ingo Molnar
2019-07-14 18:45 ` pr-tracker-bot
2019-05-05 11:00 Ingo Molnar
2019-05-05 22:10 ` pr-tracker-bot
2018-07-21 12:55 Ingo Molnar
2016-07-25 15:54 Ingo Molnar
2015-05-15 7:26 Ingo Molnar
2015-03-28 13:58 Ingo Molnar
2015-02-06 18:41 Ingo Molnar
2014-12-19 12:16 Ingo Molnar
2014-04-19 10:58 Ingo Molnar
2013-11-19 15:48 Ingo Molnar
2013-09-28 18:23 Ingo Molnar
2013-07-10 14:32 Ingo Molnar
2012-10-23 11:06 Ingo Molnar
2012-10-23 15:00 ` H. Peter Anvin
2012-10-23 15:17 ` Borislav Petkov
2011-12-20 19:30 Ingo Molnar
2011-10-13 9:00 Ingo Molnar
2011-09-30 18:22 Ingo Molnar
2011-09-30 18:59 ` Jeremy Fitzhardinge
2011-09-30 19:44 ` Thomas Gleixner
2011-07-23 8:43 Ingo Molnar
2011-02-07 15:03 Ingo Molnar
2010-12-28 22:27 Ingo Molnar
2010-12-23 13:00 Ingo Molnar
2010-12-08 7:51 Ingo Molnar
2010-10-30 18:26 Ingo Molnar
2009-09-27 8:02 Ingo Molnar
2009-06-29 8:36 Ingo Molnar
2009-03-10 18:25 [git pull] " Ingo Molnar
2009-02-28 13:02 i915 needs pgprot_writecombine() and is_io_mapping_posible() Theodore Ts'o
2009-02-28 13:34 ` [git pull] x86 fix Ingo Molnar
2009-01-13 1:17 Ingo Molnar
2008-11-07 16:30 Ingo Molnar
2008-10-04 14:55 Ingo Molnar
2008-07-01 19:57 Ingo Molnar
2008-04-26 19:47 Ingo Molnar
2008-04-26 20:15 ` Harvey Harrison
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20090810180809.GA26073@elte.hu \
--to=mingo@elte.hu \
--cc=hpa@zytor.com \
--cc=linux-kernel@vger.kernel.org \
--cc=tglx@linutronix.de \
--cc=torvalds@linux-foundation.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).