Re: [PATCH] i386: Prevent early access to TSC to avoid crash on TSCless systems
* Guillaume Chazarain <[EMAIL PROTECTED]> wrote: > >+static int tsc_enabled; > > So, now we have tsc_disable, tsc_enabled and tsc_unstable. I can > understand the latter, but this lacks orthogonality IMHO. tsc_disable should be renamed to tsc_disable_override or so, to signal that it's only the mirror of the 'notsc' flag the user passed in over the boot line. Ingo - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] i386: Prevent early access to TSC to avoid crash on TSCless systems
+static int tsc_enabled; So, now we have tsc_disable, tsc_enabled and tsc_unstable. I can understand the latter, but this lacks orthogonality IMHO. -- Guillaume - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] i386: Prevent early access to TSC to avoid crash on TSCless systems
* Thomas Gleixner <[EMAIL PROTECTED]> wrote: > commit f9690982b8c2f9a2c65acdc113e758ec356676a3 removed the check for > cpu_khz from sched_clock(), which prevented early access to the TSC by > non obvious magic. > > This is harmless as long as the CPU has a TSC. On TSCless systems this > results in an illegal instruction trap. > > Replace tsc_disabled and tsc_unstable by tsc_enabled, which is only > set when the tsc is available and not unstable. > > Signed-off-by: Thomas Gleixner <[EMAIL PROTECTED]> oops, indeed! I think this should also resolve one of the bugs (TSC-less Cyrix?) that were reported against -mm some time ago. Acked-by: Ingo Molnar <[EMAIL PROTECTED]> Ingo - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[PATCH] i386: Prevent early access to TSC to avoid crash on TSCless systems
commit f9690982b8c2f9a2c65acdc113e758ec356676a3 removed the check for
cpu_khz from sched_clock(), which prevented early access to the TSC by
non obvious magic.
This is harmless as long as the CPU has a TSC. On TSCless systems this
results in an illegal instruction trap.
Replace tsc_disabled and tsc_unstable by tsc_enabled, which is only set
when the tsc is available and not unstable.
Signed-off-by: Thomas Gleixner <[EMAIL PROTECTED]>
diff --git a/arch/i386/kernel/tsc.c b/arch/i386/kernel/tsc.c
index 0e65f7a..6cb8f53 100644
--- a/arch/i386/kernel/tsc.c
+++ b/arch/i386/kernel/tsc.c
@@ -18,6 +18,8 @@
#include "mach_timer.h"
+static int tsc_enabled;
+
/*
* On some systems the TSC frequency does not
* change with the cpu frequency. So we need
@@ -105,7 +107,7 @@ unsigned long long sched_clock(void)
/*
* Fall back to jiffies if there's no TSC available:
*/
- if (tsc_unstable || unlikely(tsc_disable))
+ if (unlikely(!tsc_enabled))
/* No locking but a rare wrong value is not a big deal: */
return (jiffies_64 - INITIAL_JIFFIES) * (10 / HZ);
@@ -283,6 +285,7 @@ void mark_tsc_unstable(void)
{
if (!tsc_unstable) {
tsc_unstable = 1;
+ tsc_enabled = 0;
/* Can be called before registration */
if (clocksource_tsc.mult)
clocksource_change_rating(_tsc, 0);
@@ -383,7 +386,9 @@ void __init tsc_init(void)
if (check_tsc_unstable()) {
clocksource_tsc.rating = 0;
clocksource_tsc.flags &= ~CLOCK_SOURCE_IS_CONTINUOUS;
- }
+ } else
+ tsc_enabled = 1;
+
clocksource_register(_tsc);
return;
-
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Please read the FAQ at http://www.tux.org/lkml/
[PATCH] i386: Prevent early access to TSC to avoid crash on TSCless systems
commit f9690982b8c2f9a2c65acdc113e758ec356676a3 removed the check for
cpu_khz from sched_clock(), which prevented early access to the TSC by
non obvious magic.
This is harmless as long as the CPU has a TSC. On TSCless systems this
results in an illegal instruction trap.
Replace tsc_disabled and tsc_unstable by tsc_enabled, which is only set
when the tsc is available and not unstable.
Signed-off-by: Thomas Gleixner [EMAIL PROTECTED]
diff --git a/arch/i386/kernel/tsc.c b/arch/i386/kernel/tsc.c
index 0e65f7a..6cb8f53 100644
--- a/arch/i386/kernel/tsc.c
+++ b/arch/i386/kernel/tsc.c
@@ -18,6 +18,8 @@
#include mach_timer.h
+static int tsc_enabled;
+
/*
* On some systems the TSC frequency does not
* change with the cpu frequency. So we need
@@ -105,7 +107,7 @@ unsigned long long sched_clock(void)
/*
* Fall back to jiffies if there's no TSC available:
*/
- if (tsc_unstable || unlikely(tsc_disable))
+ if (unlikely(!tsc_enabled))
/* No locking but a rare wrong value is not a big deal: */
return (jiffies_64 - INITIAL_JIFFIES) * (10 / HZ);
@@ -283,6 +285,7 @@ void mark_tsc_unstable(void)
{
if (!tsc_unstable) {
tsc_unstable = 1;
+ tsc_enabled = 0;
/* Can be called before registration */
if (clocksource_tsc.mult)
clocksource_change_rating(clocksource_tsc, 0);
@@ -383,7 +386,9 @@ void __init tsc_init(void)
if (check_tsc_unstable()) {
clocksource_tsc.rating = 0;
clocksource_tsc.flags = ~CLOCK_SOURCE_IS_CONTINUOUS;
- }
+ } else
+ tsc_enabled = 1;
+
clocksource_register(clocksource_tsc);
return;
-
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Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] i386: Prevent early access to TSC to avoid crash on TSCless systems
* Thomas Gleixner [EMAIL PROTECTED] wrote: commit f9690982b8c2f9a2c65acdc113e758ec356676a3 removed the check for cpu_khz from sched_clock(), which prevented early access to the TSC by non obvious magic. This is harmless as long as the CPU has a TSC. On TSCless systems this results in an illegal instruction trap. Replace tsc_disabled and tsc_unstable by tsc_enabled, which is only set when the tsc is available and not unstable. Signed-off-by: Thomas Gleixner [EMAIL PROTECTED] oops, indeed! I think this should also resolve one of the bugs (TSC-less Cyrix?) that were reported against -mm some time ago. Acked-by: Ingo Molnar [EMAIL PROTECTED] Ingo - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] i386: Prevent early access to TSC to avoid crash on TSCless systems
+static int tsc_enabled; So, now we have tsc_disable, tsc_enabled and tsc_unstable. I can understand the latter, but this lacks orthogonality IMHO. -- Guillaume - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] i386: Prevent early access to TSC to avoid crash on TSCless systems
* Guillaume Chazarain [EMAIL PROTECTED] wrote: +static int tsc_enabled; So, now we have tsc_disable, tsc_enabled and tsc_unstable. I can understand the latter, but this lacks orthogonality IMHO. tsc_disable should be renamed to tsc_disable_override or so, to signal that it's only the mirror of the 'notsc' flag the user passed in over the boot line. Ingo - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
