Fix: lttng trace-clock needs to disable preemption

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

diff --git a/wrapper/trace-clock.h b/wrapper/trace-clock.h
index b145b826571ee4fe3095973a0f6360de3344c9e6..561094b3ae924a6545cf795f0ba838040c1273fe 100644 (file)
--- a/wrapper/trace-clock.h
+++ b/wrapper/trace-clock.h
@@ -36,9 +36,11 @@
 #include <linux/version.h>
 #include <asm/local.h>
 #include "../lttng-kernel-version.h"
+#include "percpu-defs.h"
 #include "random.h"
 
-#if LTTNG_KERNEL_RANGE(3,10,0, 3,10,14) || LTTNG_KERNEL_RANGE(3,11,0, 3,11,3)
+#if ((LTTNG_KERNEL_RANGE(3,10,0, 3,10,14) && !LTTNG_RHEL_KERNEL_RANGE(3,10,0,7,0, 3,10,14,0,0)) \
+       || LTTNG_KERNEL_RANGE(3,11,0, 3,11,3))
 #error "Linux kernels 3.10 and 3.11 introduce a deadlock in the timekeeping subsystem. Fixed by commit 7bd36014460f793c19e7d6c94dab67b0afcfcb7f \"timekeeping: Fix HRTICK related deadlock from ntp lock changes\" in Linux."
 #endif
 
@@ -88,7 +90,7 @@ static inline u64 trace_clock_fixup(u64 src_now, u64 last)
 #endif /* #else #if (BITS_PER_LONG == 32) */
 
 /*
- * Always called with preemption disabled. Can be interrupted.
+ * Sometimes called with preemption enabled. Can be interrupted.
  */
 static inline u64 trace_clock_monotonic_wrapper(void)
 {
@@ -97,7 +99,8 @@ static inline u64 trace_clock_monotonic_wrapper(void)
        local_t *last_tsc;
 
        /* Use fast nmi-safe monotonic clock provided by the Linux kernel. */
-       last_tsc = &__get_cpu_var(lttng_last_tsc);
+       preempt_disable();
+       last_tsc = lttng_this_cpu_ptr(&lttng_last_tsc);
        last = local_read(last_tsc);
        /*
         * Read "last" before "now". It is not strictly required, but it ensures
@@ -110,6 +113,7 @@ static inline u64 trace_clock_monotonic_wrapper(void)
        if (((long) now - (long) last) < 0)
                now = trace_clock_fixup(now, last);
        result = local_cmpxchg(last_tsc, last, (unsigned long) now);
+       preempt_enable();
        if (result == last) {
                /* Update done. */
                return now;
@@ -140,11 +144,6 @@ static inline u64 trace_clock_monotonic_wrapper(void)
 }
 #endif /* #else #if (LINUX_VERSION_CODE >= KERNEL_VERSION(3,17,0)) */
 
-static inline u32 trace_clock_read32(void)
-{
-       return (u32) trace_clock_monotonic_wrapper();
-}
-
 static inline u64 trace_clock_read64(void)
 {
        return (u64) trace_clock_monotonic_wrapper();