X-Git-Url: https://git.lttng.org/?a=blobdiff_plain;f=liblttng-ust%2Fclock.h;h=88eca432a5733f7e4bc35f1878b911617a5119d5;hb=refs%2Fheads%2Fstable-2.5;hp=95e3e43b16d0863f412c10082151f3c924ab9cbe;hpb=28b120498f554e2478806c27f7bf7ab295f3ffdf;p=lttng-ust.git

diff --git a/liblttng-ust/clock.h b/liblttng-ust/clock.h
index 95e3e43b..88eca432 100644
--- a/liblttng-ust/clock.h
+++ b/liblttng-ust/clock.h
@@ -24,6 +24,8 @@
 #include <sys/time.h>
 #include <stdint.h>
 #include <stddef.h>
+#include <stdio.h>
+#include "lttng-ust-uuid.h"
 
 /* TRACE CLOCK */
 
@@ -50,9 +52,30 @@ uint64_t trace_clock_freq(void)
 }
 
 static __inline__
-const char *trace_clock_uuid(void)
+int trace_clock_uuid(char *uuid)
 {
-	return "CLOCK_MONOTONIC";
+	int ret = 0;
+	size_t len;
+	FILE *fp;
+
+	/*
+	 * boot_id needs to be read once before being used concurrently
+	 * to deal with a Linux kernel race. A fix is proposed for
+	 * upstream, but the work-around is needed for older kernels.
+	 */
+	fp = fopen("/proc/sys/kernel/random/boot_id", "r");
+	if (!fp) {
+		return -ENOENT;
+	}
+	len = fread(uuid, 1, LTTNG_UST_UUID_STR_LEN - 1, fp);
+	if (len < LTTNG_UST_UUID_STR_LEN - 1) {
+		ret = -EINVAL;
+		goto end;
+	}
+	uuid[LTTNG_UST_UUID_STR_LEN - 1] = '\0';
+end:
+	fclose(fp);
+	return ret;
 }
 
 #endif /* _UST_CLOCK_H */