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* sched/x86: Fix overflow in cyc2ns_offsetSalman Qazi2012-03-131-6/+2
| | | | | | | | | | | | | | | | | | | | | | | | | When a machine boots up, the TSC generally gets reset. However, when kexec is used to boot into a kernel, the TSC value would be carried over from the previous kernel. The computation of cycns_offset in set_cyc2ns_scale is prone to an overflow, if the machine has been up more than 208 days prior to the kexec. The overflow happens when we multiply *scale, even though there is enough room to store the final answer. We fix this issue by decomposing tsc_now into the quotient and remainder of division by CYC2NS_SCALE_FACTOR and then performing the multiplication separately on the two components. Refactor code to share the calculation with the previous fix in __cycles_2_ns(). Signed-off-by: Salman Qazi <sqazi@google.com> Acked-by: John Stultz <john.stultz@linaro.org> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Paul Turner <pjt@google.com> Cc: john stultz <johnstul@us.ibm.com> Link: http://lkml.kernel.org/r/20120310004027.19291.88460.stgit@dungbeetle.mtv.corp.google.com Signed-off-by: Ingo Molnar <mingo@elte.hu>
* sched, x86: Avoid unnecessary overflow in sched_clockSalman Qazi2011-11-161-1/+22
| | | | | | | | | | | | | | | | | | | | (Added the missing signed-off-by line) In hundreds of days, the __cycles_2_ns calculation in sched_clock has an overflow. cyc * per_cpu(cyc2ns, cpu) exceeds 64 bits, causing the final value to become zero. We can solve this without losing any precision. We can decompose TSC into quotient and remainder of division by the scale factor, and then use this to convert TSC into nanoseconds. Signed-off-by: Salman Qazi <sqazi@google.com> Acked-by: John Stultz <johnstul@us.ibm.com> Reviewed-by: Paul Turner <pjt@google.com> Cc: stable@kernel.org Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/20111115221121.7262.88871.stgit@dungbeetle.mtv.corp.google.com Signed-off-by: Ingo Molnar <mingo@elte.hu>
* x86, nmi_watchdog: Remove all stub function calls from old nmi_watchdogDon Zickus2010-11-181-6/+0
| | | | | | | | | | | | | | | | | | | Now that the bulk of the old nmi_watchdog is gone, remove all the stub variables and hooks associated with it. This touches lots of files mainly because of how the io_apic nmi_watchdog was implemented. Now that the io_apic nmi_watchdog is forever gone, remove all its fingers. Most of this code was not being exercised by virtue of nmi_watchdog != NMI_IO_APIC, so there shouldn't be anything to risky here. Signed-off-by: Don Zickus <dzickus@redhat.com> Cc: fweisbec@gmail.com Cc: gorcunov@openvz.org LKML-Reference: <1289578944-28564-3-git-send-email-dzickus@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* x86: Move tsc_calibration to x86_init_opsThomas Gleixner2009-08-311-5/+0
| | | | | | | | | | TSC calibration is modified by the vmware hypervisor and paravirt by separate means. Moorestown wants to add its own calibration routine as well. So make calibrate_tsc a proper x86_init_ops function and override it by paravirt or by the early setup of the vmware hypervisor. Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
* x86: Simplify timer_ack magic in time_32.cThomas Gleixner2009-08-311-2/+4
| | | | | | | | | Let the compiler optimize the timer_ack magic away in the 32bit timer interrupt and put the same code into time_64.c. It's optimized out for CONFIG_X86_IO_APIC on 32bit and for 64bit because timer_ack is const 0 in both cases. Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
* x86: Add timer_init to x86_init_opsThomas Gleixner2009-08-311-2/+1
| | | | | | | | | | | | The timer init code is convoluted with several quirks and the paravirt timer chooser. Figuring out which code path is actually taken is not for the faint hearted. Move the numaq TSC quirk to tsc_pre_init x86_init_ops function and replace the paravirt time chooser and the remaining x86 quirk with a simple x86_init_ops function. Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
* sched, x86: Fix cpufreq + sched_clock() TSC scalingPeter Zijlstra2009-06-171-1/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | For freqency dependent TSCs we only scale the cycles, we do not account for the discrepancy in absolute value. Our current formula is: time = cycles * mult (where mult is a function of the cpu-speed on variable tsc machines) Suppose our current cycle count is 10, and we have a multiplier of 5, then our time value would end up being 50. Now cpufreq comes along and changes the multiplier to say 3 or 7, which would result in our time being resp. 30 or 70. That means that we can observe random jumps in the time value due to frequency changes in both fwd and bwd direction. So what this patch does is change the formula to: time = cycles * frequency + offset And we calculate offset so that time_before == time_after, thereby ridding us of these jumps in time. [ Impact: fix/reduce sched_clock() jumps across frequency changing events ] Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu> Chucked-on-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* x86: fix mismerge in arch/x86/include/asm/timer.hStephen Rothwell2009-03-301-1/+1
| | | | | Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* x86: refactor x86_quirks supportIngo Molnar2009-02-231-0/+2
| | | | | | | | | | | | | | | | | | | | | | | | Impact: cleanup Make x86_quirks support more transparent. The highlevel methods are now named: extern void x86_quirk_pre_intr_init(void); extern void x86_quirk_intr_init(void); extern void x86_quirk_trap_init(void); extern void x86_quirk_pre_time_init(void); extern void x86_quirk_time_init(void); This makes it clear that if some platform extension has to do something here that it is considered ... weird, and is discouraged. Also remove arch_hooks.h and move it into setup.h (and other header files where appropriate). Signed-off-by: Ingo Molnar <mingo@elte.hu>
* x86: Fix ASM_X86__ header guardsH. Peter Anvin2008-10-221-3/+3
| | | | | | | | | Change header guards named "ASM_X86__*" to "_ASM_X86_*" since: a. the double underscore is ugly and pointless. b. no leading underscore violates namespace constraints. Signed-off-by: H. Peter Anvin <hpa@zytor.com>
* x86, um: ... and asm-x86 moveAl Viro2008-10-221-0/+66
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: H. Peter Anvin <hpa@zytor.com>
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