Fix: work-around upstream Linux timekeeping bug

[lttng-modules.git] / wrapper / trace-clock.h

diff --git a/wrapper/trace-clock.h b/wrapper/trace-clock.h
index 1d14cb9bd1b4457950f2aa74a933fdb6a50394ee..649c93f358d62c9bcede2cd33bd3f890ffa412ab 100644 (file)
--- a/wrapper/trace-clock.h
+++ b/wrapper/trace-clock.h
@@ -47,7 +47,16 @@
 
 extern struct lttng_trace_clock *lttng_trace_clock;
 
-#if (LINUX_VERSION_CODE >= KERNEL_VERSION(3,17,0))
+/*
+ * Upstream Linux commit 27727df240c7 ("Avoid taking lock in NMI path with
+ * CONFIG_DEBUG_TIMEKEEPING") introduces a buggy ktime_get_mono_fast_ns().
+ * This is fixed by patch "timekeeping: Fix __ktime_get_fast_ns() regression".
+ */
+#if (LINUX_VERSION_CODE >= KERNEL_VERSION(3,17,0) \
+       && !LTTNG_KERNEL_RANGE(4,8,0, 4,8,1) \
+       && !LTTNG_KERNEL_RANGE(4,7,4, 4,7,7) \
+       && !LTTNG_KERNEL_RANGE(4,4,20, 4,4,24) \
+       && !LTTNG_KERNEL_RANGE(4,1,32, 4,1,34))
 
 DECLARE_PER_CPU(local_t, lttng_last_tsc);
 
@@ -175,13 +184,13 @@ static inline const char *trace_clock_description_monotonic(void)
 #if (LINUX_VERSION_CODE >= KERNEL_VERSION(3,17,0))
 static inline int get_trace_clock(void)
 {
-       printk(KERN_WARNING "LTTng: Using mainline kernel monotonic fast clock, which is NMI-safe.\n");
+       printk_once(KERN_WARNING "LTTng: Using mainline kernel monotonic fast clock, which is NMI-safe.\n");
        return 0;
 }
 #else /* #if (LINUX_VERSION_CODE >= KERNEL_VERSION(3,17,0)) */
 static inline int get_trace_clock(void)
 {
-       printk(KERN_WARNING "LTTng: Using mainline kernel monotonic clock. NMIs will not be traced.\n");
+       printk_once(KERN_WARNING "LTTng: Using mainline kernel monotonic clock. NMIs will not be traced.\n");
        return 0;
 }
 #endif /* #else #if (LINUX_VERSION_CODE >= KERNEL_VERSION(3,17,0)) */