Merge branch 'x86-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git...

[linux-2.6] / arch / x86 / kernel / tsc_sync.c

diff --git a/arch/x86/kernel/tsc_sync.c b/arch/x86/kernel/tsc_sync.c
index 12424629af87017b87cd8cfe9666388d28c7defa..9ffb01c31c40a8c9083e9949d065a442a62f46b7 100644 (file)
--- a/arch/x86/kernel/tsc_sync.c
+++ b/arch/x86/kernel/tsc_sync.c
@@ -1 +1,189 @@
-#include "../../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();
+       /*
+        * 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();
+               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 10 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 > 10000000)
+                               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);
+               }
+       }
+       WARN(!(now-start),
+               "Warning: zero tsc calibration delta: %Ld [max: %Ld]\n",
+                       now-start, end-start);
+}
+
+/*
+ * 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();
+
+       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");
+       } else {
+               printk(" passed.\n");
+       }
+
+       /*
+        * Reset it - just in case we boot another CPU later:
+        */
+       atomic_set(&start_count, 0);
+       nr_warps = 0;
+       max_warp = 0;
+       last_tsc = 0;
+
+       /*
+        * 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
+