From 9ccc906c97e34fd91dc6aaf5b69b52d824386910 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Tue, 13 May 2008 12:31:00 +0200 Subject: x86: distangle user disabled TSC from unstable tsc_enabled is set to 0 from the command line switch "notsc" and from the mark_tsc_unstable code. Seperate those functionalities and replace tsc_enable with tsc_disable. This makes also the native_sched_clock() decision when to use TSC understandable. Preparatory patch to solve the sched_clock() issue on 32 bit. Signed-off-by: Thomas Gleixner --- arch/x86/kernel/tsc_32.c | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-) (limited to 'arch/x86/kernel/tsc_32.c') diff --git a/arch/x86/kernel/tsc_32.c b/arch/x86/kernel/tsc_32.c index e4790728b224..b087d691f165 100644 --- a/arch/x86/kernel/tsc_32.c +++ b/arch/x86/kernel/tsc_32.c @@ -14,7 +14,7 @@ #include "mach_timer.h" -static int tsc_enabled; +static int tsc_disabled; /* * On some systems the TSC frequency does not @@ -28,8 +28,8 @@ EXPORT_SYMBOL_GPL(tsc_khz); static int __init tsc_setup(char *str) { printk(KERN_WARNING "notsc: Kernel compiled with CONFIG_X86_TSC, " - "cannot disable TSC completely.\n"); - mark_tsc_unstable("user disabled TSC"); + "cannot disable TSC completely.\n"); + tsc_disabled = 1; return 1; } #else @@ -120,7 +120,7 @@ unsigned long long native_sched_clock(void) * very important for it to be as fast as the platform * can achive it. ) */ - if (unlikely(!tsc_enabled && !tsc_unstable)) + if (unlikely(tsc_disabled)) /* No locking but a rare wrong value is not a big deal: */ return (jiffies_64 - INITIAL_JIFFIES) * (1000000000 / HZ); @@ -322,7 +322,6 @@ void mark_tsc_unstable(char *reason) { if (!tsc_unstable) { tsc_unstable = 1; - tsc_enabled = 0; printk("Marking TSC unstable due to: %s.\n", reason); /* Can be called before registration */ if (clocksource_tsc.mult) @@ -336,7 +335,7 @@ EXPORT_SYMBOL_GPL(mark_tsc_unstable); static int __init dmi_mark_tsc_unstable(const struct dmi_system_id *d) { printk(KERN_NOTICE "%s detected: marking TSC unstable.\n", - d->ident); + d->ident); tsc_unstable = 1; return 0; } @@ -403,8 +402,11 @@ void __init tsc_init(void) { int cpu; - if (!cpu_has_tsc) + if (!cpu_has_tsc || tsc_disabled) { + /* Disable the TSC in case of !cpu_has_tsc */ + tsc_disabled = 1; return; + } cpu_khz = calculate_cpu_khz(); tsc_khz = cpu_khz; @@ -441,8 +443,6 @@ 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); } -- cgit v1.2.3 From 74dc51a3de06aa516e3b9fdc4017b2aeb38bf44b Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Sun, 18 May 2008 22:17:59 +0200 Subject: x86: disable TSC for sched_clock() when calibration failed When the TSC calibration fails then TSC is still used in sched_clock(). Disable it completely in that case. Signed-off-by: Thomas Gleixner Cc: stable@kernel.org --- arch/x86/kernel/tsc_32.c | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'arch/x86/kernel/tsc_32.c') diff --git a/arch/x86/kernel/tsc_32.c b/arch/x86/kernel/tsc_32.c index b087d691f165..068759db63dd 100644 --- a/arch/x86/kernel/tsc_32.c +++ b/arch/x86/kernel/tsc_32.c @@ -413,6 +413,11 @@ void __init tsc_init(void) if (!cpu_khz) { mark_tsc_unstable("could not calculate TSC khz"); + /* + * We need to disable the TSC completely in this case + * to prevent sched_clock() from using it. + */ + tsc_disabled = 1; return; } -- cgit v1.2.3