1 files changed, 187 insertions, 1 deletions

diff --git a/arch/x86/kernel/tsc_sync.c b/arch/x86/kernel/tsc_sync.c
index 12424629af87..355f5f506c81 100644
--- a/arch/x86/kernel/tsc_sync.c
+++ b/arch/x86/kernel/tsc_sync.c
@@ -1 +1,187 @@
-#include "../../x86_64/kernel/tsc_sync.c"
+/*
+ * 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 <linux/spinlock.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/smp.h>
+#include <linux/nmi.h>
+#include <asm/tsc.h>
+
+/*
+ * 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 + tsc_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("check_tsc_sync_source failed");
+                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
+