From: Ingo Molnar make the TSC synchronization code more robust, and unify it between x86_64 and i386. The biggest change is the removal of the 'fix up TSCs' code on x86_64 and i386, in some rare cases it was /causing/ time-warps on SMP systems. The new code only checks for TSC asynchronity - and if it can prove a time-warp (if it can observe the TSC going backwards when going from one CPU to another within a critical section), then the TSC clock-source is turned off. The TSC synchronization-checking code also got moved into a separate file. Signed-off-by: Ingo Molnar Signed-off-by: Thomas Gleixner --- arch/i386/kernel/Makefile | 2 arch/i386/kernel/smpboot.c | 178 ++------------------------------ arch/i386/kernel/tsc.c | 4 arch/i386/kernel/tsc_sync.c | 1 arch/x86_64/kernel/Makefile | 2 arch/x86_64/kernel/smpboot.c | 230 ++---------------------------------------- arch/x86_64/kernel/time.c | 11 ++ arch/x86_64/kernel/tsc_sync.c | 187 ++++++++++++++++++++++++++++++++++ include/asm-i386/tsc.h | 49 -------- include/asm-x86_64/proto.h | 2 include/asm-x86_64/timex.h | 26 ---- include/asm-x86_64/tsc.h | 66 ++++++++++++ 12 files changed, 295 insertions(+), 463 deletions(-) Index: linux-2.6.20-rc4-mm1-bo/arch/i386/kernel/Makefile =================================================================== --- linux-2.6.20-rc4-mm1-bo.orig/arch/i386/kernel/Makefile +++ linux-2.6.20-rc4-mm1-bo/arch/i386/kernel/Makefile @@ -18,7 +18,7 @@ obj-$(CONFIG_X86_MSR) += msr.o obj-$(CONFIG_X86_CPUID) += cpuid.o obj-$(CONFIG_MICROCODE) += microcode.o obj-$(CONFIG_APM) += apm.o -obj-$(CONFIG_X86_SMP) += smp.o smpboot.o +obj-$(CONFIG_X86_SMP) += smp.o smpboot.o tsc_sync.o obj-$(CONFIG_X86_TRAMPOLINE) += trampoline.o obj-$(CONFIG_X86_MPPARSE) += mpparse.o obj-$(CONFIG_X86_LOCAL_APIC) += apic.o nmi.o Index: linux-2.6.20-rc4-mm1-bo/arch/i386/kernel/smpboot.c =================================================================== --- linux-2.6.20-rc4-mm1-bo.orig/arch/i386/kernel/smpboot.c +++ linux-2.6.20-rc4-mm1-bo/arch/i386/kernel/smpboot.c @@ -93,12 +93,6 @@ cpumask_t cpu_possible_map; EXPORT_SYMBOL(cpu_possible_map); static cpumask_t smp_commenced_mask; -/* TSC's upper 32 bits can't be written in eariler CPU (before prescott), there - * is no way to resync one AP against BP. TBD: for prescott and above, we - * should use IA64's algorithm - */ -static int __devinitdata tsc_sync_disabled; - /* Per CPU bogomips and other parameters */ struct cpuinfo_x86 cpu_data[NR_CPUS] __cacheline_aligned; EXPORT_SYMBOL(cpu_data); @@ -215,151 +209,6 @@ valid_k7: ; } -/* - * TSC synchronization. - * - * We first check whether all CPUs have their TSC's synchronized, - * then we print a warning if not, and always resync. - */ - -static struct { - atomic_t start_flag; - atomic_t count_start; - atomic_t count_stop; - unsigned long long values[NR_CPUS]; -} tsc __cpuinitdata = { - .start_flag = ATOMIC_INIT(0), - .count_start = ATOMIC_INIT(0), - .count_stop = ATOMIC_INIT(0), -}; - -#define NR_LOOPS 5 - -static void __init synchronize_tsc_bp(void) -{ - int i; - unsigned long long t0; - unsigned long long sum, avg; - long long delta; - unsigned int one_usec; - int buggy = 0; - - printk(KERN_INFO "checking TSC synchronization across %u CPUs: ", num_booting_cpus()); - - /* convert from kcyc/sec to cyc/usec */ - one_usec = cpu_khz / 1000; - - atomic_set(&tsc.start_flag, 1); - wmb(); - - /* - * We loop a few times to get a primed instruction cache, - * then the last pass is more or less synchronized and - * the BP and APs set their cycle counters to zero all at - * once. This reduces the chance of having random offsets - * between the processors, and guarantees that the maximum - * delay between the cycle counters is never bigger than - * the latency of information-passing (cachelines) between - * two CPUs. - */ - for (i = 0; i < NR_LOOPS; i++) { - /* - * all APs synchronize but they loop on '== num_cpus' - */ - while (atomic_read(&tsc.count_start) != num_booting_cpus()-1) - cpu_relax(); - atomic_set(&tsc.count_stop, 0); - wmb(); - /* - * this lets the APs save their current TSC: - */ - atomic_inc(&tsc.count_start); - - rdtscll(tsc.values[smp_processor_id()]); - /* - * We clear the TSC in the last loop: - */ - if (i == NR_LOOPS-1) - write_tsc(0, 0); - - /* - * Wait for all APs to leave the synchronization point: - */ - while (atomic_read(&tsc.count_stop) != num_booting_cpus()-1) - cpu_relax(); - atomic_set(&tsc.count_start, 0); - wmb(); - atomic_inc(&tsc.count_stop); - } - - sum = 0; - for (i = 0; i < NR_CPUS; i++) { - if (cpu_isset(i, cpu_callout_map)) { - t0 = tsc.values[i]; - sum += t0; - } - } - avg = sum; - do_div(avg, num_booting_cpus()); - - for (i = 0; i < NR_CPUS; i++) { - if (!cpu_isset(i, cpu_callout_map)) - continue; - delta = tsc.values[i] - avg; - if (delta < 0) - delta = -delta; - /* - * We report bigger than 2 microseconds clock differences. - */ - if (delta > 2*one_usec) { - long long realdelta; - - if (!buggy) { - buggy = 1; - printk("\n"); - } - realdelta = delta; - do_div(realdelta, one_usec); - if (tsc.values[i] < avg) - realdelta = -realdelta; - - if (realdelta) - printk(KERN_INFO "CPU#%d had %Ld usecs TSC " - "skew, fixed it up.\n", i, realdelta); - } - } - if (!buggy) - printk("passed.\n"); -} - -static void __cpuinit synchronize_tsc_ap(void) -{ - int i; - - /* - * Not every cpu is online at the time - * this gets called, so we first wait for the BP to - * finish SMP initialization: - */ - while (!atomic_read(&tsc.start_flag)) - cpu_relax(); - - for (i = 0; i < NR_LOOPS; i++) { - atomic_inc(&tsc.count_start); - while (atomic_read(&tsc.count_start) != num_booting_cpus()) - cpu_relax(); - - rdtscll(tsc.values[smp_processor_id()]); - if (i == NR_LOOPS-1) - write_tsc(0, 0); - - atomic_inc(&tsc.count_stop); - while (atomic_read(&tsc.count_stop) != num_booting_cpus()) - cpu_relax(); - } -} -#undef NR_LOOPS - extern void calibrate_delay(void); static atomic_t init_deasserted; @@ -445,12 +294,6 @@ static void __cpuinit smp_callin(void) * Allow the master to continue. */ cpu_set(cpuid, cpu_callin_map); - - /* - * Synchronize the TSC with the BP - */ - if (cpu_has_tsc && cpu_khz && !tsc_sync_disabled) - synchronize_tsc_ap(); } static int cpucount; @@ -553,6 +396,11 @@ static void __cpuinit start_secondary(vo smp_callin(); while (!cpu_isset(smp_processor_id(), smp_commenced_mask)) rep_nop(); + /* + * Check TSC synchronization with the BP: + */ + check_tsc_sync_target(); + setup_secondary_clock(); if (nmi_watchdog == NMI_IO_APIC) { disable_8259A_irq(0); @@ -1122,8 +970,6 @@ static int __cpuinit __smp_prepare_cpu(i info.cpu = cpu; INIT_WORK(&info.task, do_warm_boot_cpu); - tsc_sync_disabled = 1; - /* init low mem mapping */ clone_pgd_range(swapper_pg_dir, swapper_pg_dir + USER_PGD_PTRS, min_t(unsigned long, KERNEL_PGD_PTRS, USER_PGD_PTRS)); @@ -1131,7 +977,6 @@ static int __cpuinit __smp_prepare_cpu(i schedule_work(&info.task); wait_for_completion(&done); - tsc_sync_disabled = 0; zap_low_mappings(); ret = 0; exit: @@ -1328,12 +1173,6 @@ static void __init smp_boot_cpus(unsigne smpboot_setup_io_apic(); setup_boot_clock(); - - /* - * Synchronize the TSC with the AP - */ - if (cpu_has_tsc && cpucount && cpu_khz) - synchronize_tsc_bp(); } /* These are wrappers to interface to the new boot process. Someone @@ -1468,9 +1307,16 @@ int __cpuinit __cpu_up(unsigned int cpu) } local_irq_enable(); + per_cpu(cpu_state, cpu) = CPU_UP_PREPARE; /* Unleash the CPU! */ cpu_set(cpu, smp_commenced_mask); + + /* + * Check TSC synchronization with the AP: + */ + check_tsc_sync_source(cpu); + while (!cpu_isset(cpu, cpu_online_map)) cpu_relax(); return 0; Index: linux-2.6.20-rc4-mm1-bo/arch/i386/kernel/tsc.c =================================================================== --- linux-2.6.20-rc4-mm1-bo.orig/arch/i386/kernel/tsc.c +++ linux-2.6.20-rc4-mm1-bo/arch/i386/kernel/tsc.c @@ -407,8 +407,10 @@ out: * Make an educated guess if the TSC is trustworthy and synchronized * over all CPUs. */ -static __init int unsynchronized_tsc(void) +__cpuinit int unsynchronized_tsc(void) { + if (!cpu_has_tsc || tsc_unstable) + return 1; /* * Intel systems are normally all synchronized. * Exceptions must mark TSC as unstable: Index: linux-2.6.20-rc4-mm1-bo/arch/i386/kernel/tsc_sync.c =================================================================== --- /dev/null +++ linux-2.6.20-rc4-mm1-bo/arch/i386/kernel/tsc_sync.c @@ -0,0 +1 @@ +#include "../../x86_64/kernel/tsc_sync.c" Index: linux-2.6.20-rc4-mm1-bo/arch/x86_64/kernel/Makefile =================================================================== --- linux-2.6.20-rc4-mm1-bo.orig/arch/x86_64/kernel/Makefile +++ linux-2.6.20-rc4-mm1-bo/arch/x86_64/kernel/Makefile @@ -19,7 +19,7 @@ obj-$(CONFIG_ACPI) += acpi/ obj-$(CONFIG_X86_MSR) += msr.o obj-$(CONFIG_MICROCODE) += microcode.o obj-$(CONFIG_X86_CPUID) += cpuid.o -obj-$(CONFIG_SMP) += smp.o smpboot.o trampoline.o +obj-$(CONFIG_SMP) += smp.o smpboot.o trampoline.o tsc_sync.o obj-y += apic.o nmi.o obj-y += io_apic.o mpparse.o genapic.o genapic_flat.o obj-$(CONFIG_KEXEC) += machine_kexec.o relocate_kernel.o crash.o Index: linux-2.6.20-rc4-mm1-bo/arch/x86_64/kernel/smpboot.c =================================================================== --- linux-2.6.20-rc4-mm1-bo.orig/arch/x86_64/kernel/smpboot.c +++ linux-2.6.20-rc4-mm1-bo/arch/x86_64/kernel/smpboot.c @@ -147,217 +147,6 @@ static void __cpuinit smp_store_cpu_info print_cpu_info(c); } -/* - * New Funky TSC sync algorithm borrowed from IA64. - * Main advantage is that it doesn't reset the TSCs fully and - * in general looks more robust and it works better than my earlier - * attempts. I believe it was written by David Mosberger. Some minor - * adjustments for x86-64 by me -AK - * - * Original comment reproduced below. - * - * Synchronize TSC of the current (slave) CPU with the TSC of the - * MASTER CPU (normally the time-keeper CPU). We use a closed loop to - * eliminate the possibility of unaccounted-for errors (such as - * getting a machine check in the middle of a calibration step). The - * basic idea is for the slave to ask the master what itc value it has - * and to read its own itc before and after the master responds. Each - * iteration gives us three timestamps: - * - * slave master - * - * t0 ---\ - * ---\ - * ---> - * tm - * /--- - * /--- - * t1 <--- - * - * - * The goal is to adjust the slave's TSC such that tm falls exactly - * half-way between t0 and t1. If we achieve this, the clocks are - * synchronized provided the interconnect between the slave and the - * master is symmetric. Even if the interconnect were asymmetric, we - * would still know that the synchronization error is smaller than the - * roundtrip latency (t0 - t1). - * - * When the interconnect is quiet and symmetric, this lets us - * synchronize the TSC to within one or two cycles. However, we can - * only *guarantee* that the synchronization is accurate to within a - * round-trip time, which is typically in the range of several hundred - * cycles (e.g., ~500 cycles). In practice, this means that the TSCs - * are usually almost perfectly synchronized, but we shouldn't assume - * that the accuracy is much better than half a micro second or so. - * - * [there are other errors like the latency of RDTSC and of the - * WRMSR. These can also account to hundreds of cycles. So it's - * probably worse. It claims 153 cycles error on a dual Opteron, - * but I suspect the numbers are actually somewhat worse -AK] - */ - -#define MASTER 0 -#define SLAVE (SMP_CACHE_BYTES/8) - -/* Intentionally don't use cpu_relax() while TSC synchronization - because we don't want to go into funky power save modi or cause - hypervisors to schedule us away. Going to sleep would likely affect - latency and low latency is the primary objective here. -AK */ -#define no_cpu_relax() barrier() - -static __cpuinitdata DEFINE_SPINLOCK(tsc_sync_lock); -static volatile __cpuinitdata unsigned long go[SLAVE + 1]; -static int notscsync __cpuinitdata; - -#undef DEBUG_TSC_SYNC - -#define NUM_ROUNDS 64 /* magic value */ -#define NUM_ITERS 5 /* likewise */ - -/* Callback on boot CPU */ -static __cpuinit void sync_master(void *arg) -{ - unsigned long flags, i; - - go[MASTER] = 0; - - local_irq_save(flags); - { - for (i = 0; i < NUM_ROUNDS*NUM_ITERS; ++i) { - while (!go[MASTER]) - no_cpu_relax(); - go[MASTER] = 0; - rdtscll(go[SLAVE]); - } - } - local_irq_restore(flags); -} - -/* - * Return the number of cycles by which our tsc differs from the tsc - * on the master (time-keeper) CPU. A positive number indicates our - * tsc is ahead of the master, negative that it is behind. - */ -static inline long -get_delta(long *rt, long *master) -{ - unsigned long best_t0 = 0, best_t1 = ~0UL, best_tm = 0; - unsigned long tcenter, t0, t1, tm; - int i; - - for (i = 0; i < NUM_ITERS; ++i) { - rdtscll(t0); - go[MASTER] = 1; - while (!(tm = go[SLAVE])) - no_cpu_relax(); - go[SLAVE] = 0; - rdtscll(t1); - - if (t1 - t0 < best_t1 - best_t0) - best_t0 = t0, best_t1 = t1, best_tm = tm; - } - - *rt = best_t1 - best_t0; - *master = best_tm - best_t0; - - /* average best_t0 and best_t1 without overflow: */ - tcenter = (best_t0/2 + best_t1/2); - if (best_t0 % 2 + best_t1 % 2 == 2) - ++tcenter; - return tcenter - best_tm; -} - -static __cpuinit void sync_tsc(unsigned int master) -{ - int i, done = 0; - long delta, adj, adjust_latency = 0; - unsigned long flags, rt, master_time_stamp, bound; -#ifdef DEBUG_TSC_SYNC - static struct syncdebug { - long rt; /* roundtrip time */ - long master; /* master's timestamp */ - long diff; /* difference between midpoint and master's timestamp */ - long lat; /* estimate of tsc adjustment latency */ - } t[NUM_ROUNDS] __cpuinitdata; -#endif - - printk(KERN_INFO "CPU %d: Syncing TSC to CPU %u.\n", - smp_processor_id(), master); - - go[MASTER] = 1; - - /* It is dangerous to broadcast IPI as cpus are coming up, - * as they may not be ready to accept them. So since - * we only need to send the ipi to the boot cpu direct - * the message, and avoid the race. - */ - smp_call_function_single(master, sync_master, NULL, 1, 0); - - while (go[MASTER]) /* wait for master to be ready */ - no_cpu_relax(); - - spin_lock_irqsave(&tsc_sync_lock, flags); - { - for (i = 0; i < NUM_ROUNDS; ++i) { - delta = get_delta(&rt, &master_time_stamp); - if (delta == 0) { - done = 1; /* let's lock on to this... */ - bound = rt; - } - - if (!done) { - unsigned long t; - if (i > 0) { - adjust_latency += -delta; - adj = -delta + adjust_latency/4; - } else - adj = -delta; - - rdtscll(t); - wrmsrl(MSR_IA32_TSC, t + adj); - } -#ifdef DEBUG_TSC_SYNC - t[i].rt = rt; - t[i].master = master_time_stamp; - t[i].diff = delta; - t[i].lat = adjust_latency/4; -#endif - } - } - spin_unlock_irqrestore(&tsc_sync_lock, flags); - -#ifdef DEBUG_TSC_SYNC - for (i = 0; i < NUM_ROUNDS; ++i) - printk("rt=%5ld master=%5ld diff=%5ld adjlat=%5ld\n", - t[i].rt, t[i].master, t[i].diff, t[i].lat); -#endif - - printk(KERN_INFO - "CPU %d: synchronized TSC with CPU %u (last diff %ld cycles, " - "maxerr %lu cycles)\n", - smp_processor_id(), master, delta, rt); -} - -static void __cpuinit tsc_sync_wait(void) -{ - /* - * When the CPU has synchronized TSCs assume the BIOS - * or the hardware already synced. Otherwise we could - * mess up a possible perfect synchronization with a - * not-quite-perfect algorithm. - */ - if (notscsync || !cpu_has_tsc || !unsynchronized_tsc()) - return; - sync_tsc(0); -} - -static __init int notscsync_setup(char *s) -{ - notscsync = 1; - return 1; -} -__setup("notscsync", notscsync_setup); - static atomic_t init_deasserted __cpuinitdata; /* @@ -545,6 +334,11 @@ void __cpuinit start_secondary(void) /* otherwise gcc will move up the smp_processor_id before the cpu_init */ barrier(); + /* + * Check TSC sync first: + */ + check_tsc_sync_target(); + Dprintk("cpu %d: setting up apic clock\n", smp_processor_id()); setup_secondary_APIC_clock(); @@ -564,14 +358,6 @@ void __cpuinit start_secondary(void) */ set_cpu_sibling_map(smp_processor_id()); - /* - * Wait for TSC sync to not schedule things before. - * We still process interrupts, which could see an inconsistent - * time in that window unfortunately. - * Do this here because TSC sync has global unprotected state. - */ - tsc_sync_wait(); - /* * We need to hold call_lock, so there is no inconsistency * between the time smp_call_function() determines number of @@ -591,6 +377,7 @@ void __cpuinit start_secondary(void) cpu_set(smp_processor_id(), cpu_online_map); per_cpu(cpu_state, smp_processor_id()) = CPU_ONLINE; spin_unlock(&vector_lock); + unlock_ipi_call_lock(); cpu_idle(); @@ -1166,6 +953,11 @@ int __cpuinit __cpu_up(unsigned int cpu) /* Unleash the CPU! */ Dprintk("waiting for cpu %d\n", cpu); + /* + * Make sure and check TSC sync: + */ + check_tsc_sync_source(cpu); + while (!cpu_isset(cpu, cpu_online_map)) cpu_relax(); err = 0; Index: linux-2.6.20-rc4-mm1-bo/arch/x86_64/kernel/time.c =================================================================== --- linux-2.6.20-rc4-mm1-bo.orig/arch/x86_64/kernel/time.c +++ linux-2.6.20-rc4-mm1-bo/arch/x86_64/kernel/time.c @@ -939,12 +939,23 @@ void __init time_init(void) #endif } +static int tsc_unstable = 0; + +void mark_tsc_unstable(void) +{ + tsc_unstable = 1; +} +EXPORT_SYMBOL_GPL(mark_tsc_unstable); + /* * Make an educated guess if the TSC is trustworthy and synchronized * over all CPUs. */ __cpuinit int unsynchronized_tsc(void) { + if (tsc_unstable) + return 1; + #ifdef CONFIG_SMP if (apic_is_clustered_box()) return 1; Index: linux-2.6.20-rc4-mm1-bo/arch/x86_64/kernel/tsc_sync.c =================================================================== --- /dev/null +++ linux-2.6.20-rc4-mm1-bo/arch/x86_64/kernel/tsc_sync.c @@ -0,0 +1,187 @@ +/* + * arch/x86_64/kernel/tsc_sync.c: check TSC synchronization. + * + * Copyright (C) 2006, Red Hat, Inc., Ingo Molnar + * + * We check whether all boot CPUs have their TSC's synchronized, + * print a warning if not and turn off the TSC clock-source. + * + * The warp-check is point-to-point between two CPUs, the CPU + * initiating the bootup is the 'source CPU', the freshly booting + * CPU is the 'target CPU'. + * + * Only two CPUs may participate - they can enter in any order. + * ( The serial nature of the boot logic and the CPU hotplug lock + * protects against more than 2 CPUs entering this code. ) + */ +#include +#include +#include +#include +#include +#include + +/* + * Entry/exit counters that make sure that both CPUs + * run the measurement code at once: + */ +static __cpuinitdata atomic_t start_count; +static __cpuinitdata atomic_t stop_count; + +/* + * We use a raw spinlock in this exceptional case, because + * we want to have the fastest, inlined, non-debug version + * of a critical section, to be able to prove TSC time-warps: + */ +static __cpuinitdata raw_spinlock_t sync_lock = __RAW_SPIN_LOCK_UNLOCKED; +static __cpuinitdata cycles_t last_tsc; +static __cpuinitdata cycles_t max_warp; +static __cpuinitdata int nr_warps; + +/* + * TSC-warp measurement loop running on both CPUs: + */ +static __cpuinit void check_tsc_warp(void) +{ + cycles_t start, now, prev, end; + int i; + + start = get_cycles_sync(); + /* + * The measurement runs for 20 msecs: + */ + end = start + cpu_khz * 20ULL; + now = start; + + for (i = 0; ; i++) { + /* + * We take the global lock, measure TSC, save the + * previous TSC that was measured (possibly on + * another CPU) and update the previous TSC timestamp. + */ + __raw_spin_lock(&sync_lock); + prev = last_tsc; + now = get_cycles_sync(); + last_tsc = now; + __raw_spin_unlock(&sync_lock); + + /* + * Be nice every now and then (and also check whether + * measurement is done [we also insert a 100 million + * loops safety exit, so we dont lock up in case the + * TSC readout is totally broken]): + */ + if (unlikely(!(i & 7))) { + if (now > end || i > 100000000) + break; + cpu_relax(); + touch_nmi_watchdog(); + } + /* + * Outside the critical section we can now see whether + * we saw a time-warp of the TSC going backwards: + */ + if (unlikely(prev > now)) { + __raw_spin_lock(&sync_lock); + max_warp = max(max_warp, prev - now); + nr_warps++; + __raw_spin_unlock(&sync_lock); + } + + } +} + +/* + * Source CPU calls into this - it waits for the freshly booted + * target CPU to arrive and then starts the measurement: + */ +void __cpuinit check_tsc_sync_source(int cpu) +{ + int cpus = 2; + + /* + * No need to check if we already know that the TSC is not + * synchronized: + */ + if (unsynchronized_tsc()) + return; + + printk(KERN_INFO "checking TSC synchronization [CPU#%d -> CPU#%d]:", + smp_processor_id(), cpu); + + /* + * Reset it - in case this is a second bootup: + */ + atomic_set(&stop_count, 0); + + /* + * Wait for the target to arrive: + */ + while (atomic_read(&start_count) != cpus-1) + cpu_relax(); + /* + * Trigger the target to continue into the measurement too: + */ + atomic_inc(&start_count); + + check_tsc_warp(); + + while (atomic_read(&stop_count) != cpus-1) + cpu_relax(); + + /* + * Reset it - just in case we boot another CPU later: + */ + atomic_set(&start_count, 0); + + if (nr_warps) { + printk("\n"); + printk(KERN_WARNING "Measured %Ld cycles TSC warp between CPUs," + " turning off TSC clock.\n", max_warp); + mark_tsc_unstable(); + nr_warps = 0; + max_warp = 0; + last_tsc = 0; + } else { + printk(" passed.\n"); + } + + /* + * Let the target continue with the bootup: + */ + atomic_inc(&stop_count); +} + +/* + * Freshly booted CPUs call into this: + */ +void __cpuinit check_tsc_sync_target(void) +{ + int cpus = 2; + + if (unsynchronized_tsc()) + return; + + /* + * Register this CPU's participation and wait for the + * source CPU to start the measurement: + */ + atomic_inc(&start_count); + while (atomic_read(&start_count) != cpus) + cpu_relax(); + + check_tsc_warp(); + + /* + * Ok, we are done: + */ + atomic_inc(&stop_count); + + /* + * Wait for the source CPU to print stuff: + */ + while (atomic_read(&stop_count) != cpus) + cpu_relax(); +} +#undef NR_LOOPS + Index: linux-2.6.20-rc4-mm1-bo/include/asm-i386/tsc.h =================================================================== --- linux-2.6.20-rc4-mm1-bo.orig/include/asm-i386/tsc.h +++ linux-2.6.20-rc4-mm1-bo/include/asm-i386/tsc.h @@ -1,48 +1 @@ -/* - * linux/include/asm-i386/tsc.h - * - * i386 TSC related functions - */ -#ifndef _ASM_i386_TSC_H -#define _ASM_i386_TSC_H - -#include - -/* - * Standard way to access the cycle counter on i586+ CPUs. - * Currently only used on SMP. - * - * If you really have a SMP machine with i486 chips or older, - * compile for that, and this will just always return zero. - * That's ok, it just means that the nicer scheduling heuristics - * won't work for you. - * - * We only use the low 32 bits, and we'd simply better make sure - * that we reschedule before that wraps. Scheduling at least every - * four billion cycles just basically sounds like a good idea, - * regardless of how fast the machine is. - */ -typedef unsigned long long cycles_t; - -extern unsigned int cpu_khz; -extern unsigned int tsc_khz; - -static inline cycles_t get_cycles(void) -{ - unsigned long long ret = 0; - -#ifndef CONFIG_X86_TSC - if (!cpu_has_tsc) - return 0; -#endif - -#if defined(CONFIG_X86_GENERIC) || defined(CONFIG_X86_TSC) - rdtscll(ret); -#endif - return ret; -} - -extern void tsc_init(void); -extern void mark_tsc_unstable(void); - -#endif +#include Index: linux-2.6.20-rc4-mm1-bo/include/asm-x86_64/proto.h =================================================================== --- linux-2.6.20-rc4-mm1-bo.orig/include/asm-x86_64/proto.h +++ linux-2.6.20-rc4-mm1-bo/include/asm-x86_64/proto.h @@ -91,8 +91,6 @@ extern void check_efer(void); extern int unhandled_signal(struct task_struct *tsk, int sig); -extern int unsynchronized_tsc(void); - extern void select_idle_routine(const struct cpuinfo_x86 *c); extern unsigned long table_start, table_end; Index: linux-2.6.20-rc4-mm1-bo/include/asm-x86_64/timex.h =================================================================== --- linux-2.6.20-rc4-mm1-bo.orig/include/asm-x86_64/timex.h +++ linux-2.6.20-rc4-mm1-bo/include/asm-x86_64/timex.h @@ -12,35 +12,11 @@ #include #include #include +#include #include #define CLOCK_TICK_RATE PIT_TICK_RATE /* Underlying HZ */ -typedef unsigned long long cycles_t; - -static inline cycles_t get_cycles (void) -{ - unsigned long long ret; - - rdtscll(ret); - return ret; -} - -/* Like get_cycles, but make sure the CPU is synchronized. */ -static __always_inline cycles_t get_cycles_sync(void) -{ - unsigned long long ret; - unsigned eax; - /* Don't do an additional sync on CPUs where we know - RDTSC is already synchronous. */ - alternative_io("cpuid", ASM_NOP2, X86_FEATURE_SYNC_RDTSC, - "=a" (eax), "0" (1) : "ebx","ecx","edx","memory"); - rdtscll(ret); - return ret; -} - -extern unsigned int cpu_khz; - extern int read_current_timer(unsigned long *timer_value); #define ARCH_HAS_READ_CURRENT_TIMER 1 Index: linux-2.6.20-rc4-mm1-bo/include/asm-x86_64/tsc.h =================================================================== --- /dev/null +++ linux-2.6.20-rc4-mm1-bo/include/asm-x86_64/tsc.h @@ -0,0 +1,66 @@ +/* + * linux/include/asm-x86_64/tsc.h + * + * x86_64 TSC related functions + */ +#ifndef _ASM_x86_64_TSC_H +#define _ASM_x86_64_TSC_H + +#include + +/* + * Standard way to access the cycle counter. + */ +typedef unsigned long long cycles_t; + +extern unsigned int cpu_khz; +extern unsigned int tsc_khz; + +static inline cycles_t get_cycles(void) +{ + unsigned long long ret = 0; + +#ifndef CONFIG_X86_TSC + if (!cpu_has_tsc) + return 0; +#endif + +#if defined(CONFIG_X86_GENERIC) || defined(CONFIG_X86_TSC) + rdtscll(ret); +#endif + return ret; +} + +/* Like get_cycles, but make sure the CPU is synchronized. */ +static __always_inline cycles_t get_cycles_sync(void) +{ + unsigned long long ret; +#ifdef X86_FEATURE_SYNC_RDTSC + unsigned eax; + + /* + * Don't do an additional sync on CPUs where we know + * RDTSC is already synchronous: + */ + alternative_io("cpuid", ASM_NOP2, X86_FEATURE_SYNC_RDTSC, + "=a" (eax), "0" (1) : "ebx","ecx","edx","memory"); +#else + sync_core(); +#endif + rdtscll(ret); + + return ret; +} + +extern void tsc_init(void); +extern void mark_tsc_unstable(void); +extern int unsynchronized_tsc(void); + +/* + * Boot-time check whether the TSCs are synchronized across + * all CPUs/cores: + */ +extern void check_tsc_sync_source(int cpu); +extern void check_tsc_sync_target(void); + +#endif -- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/