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 1b2821a19a8b7fde4a315721944d0d66405062bb..561094b3ae924a6545cf795f0ba838040c1273fe 100644 (file)
--- a/wrapper/trace-clock.h
+++ b/wrapper/trace-clock.h
@@ -39,7 +39,8 @@
 #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
 
@@ -89,7 +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)
 {
@@ -98,6 +99,7 @@ static inline u64 trace_clock_monotonic_wrapper(void)
        local_t *last_tsc;
 
        /* Use fast nmi-safe monotonic clock provided by the Linux kernel. */
+       preempt_disable();
        last_tsc = lttng_this_cpu_ptr(&lttng_last_tsc);
        last = local_read(last_tsc);
        /*
@@ -111,6 +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;