From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Wed, 9 Feb 2011 19:09:11 +0000 (-0500)
Subject: Add getcpu error validation
X-Git-Tag: v0.12~71
X-Git-Url: http://git.lttng.org/?p=ust.git;a=commitdiff_plain;h=8f09cb9340387a52b483752c5d2d6c36035b26bc

Add getcpu error validation

This check is important for the case where getcpu(2) is not implemented by the
Kernel. So, the CPU 0 is the fallback.

Reported-by: David Goulet <david.goulet@polymtl.ca>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---

diff --git a/libust/tracer.h b/libust/tracer.h
index 64996b2..2f489f6 100644
--- a/libust/tracer.h
+++ b/libust/tracer.h
@@ -343,21 +343,36 @@ static __inline__ void ltt_write_trace_header(struct ust_trace *trace,
 	header->freq_scale = trace->freq_scale;
 }
 
+#ifndef UST_VALGRIND
+
 static __inline__ int ust_get_cpu(void)
 {
-#ifndef UST_VALGRIND
-	return sched_getcpu();
-#else
-	/* Valgrind does not support the sched_getcpu() vsyscall.
+	int cpu;
+
+	cpu = sched_getcpu();
+	if (likely(cpu >= 0))
+		return cpu;
+	/*
+	 * If getcpu(2) is not implemented in the Kernel use CPU 0 as fallback.
+	 */
+	return 0;
+}
+
+#else	/* #else #ifndef UST_VALGRIND */
+
+static __inline__ int ust_get_cpu(void)
+{
+	/*
+	 * Valgrind does not support the sched_getcpu() vsyscall.
 	 * It causes it to detect a segfault in the program and stop it.
 	 * So if we want to check libust with valgrind, we have to refrain
 	 * from using this call. TODO: it would probably be better to return
 	 * other values too, to better test it.
 	 */
 	return 0;
-#endif
 }
 
+#endif	/* #else #ifndef UST_VALGRIND */
 
 /*
  * Size reserved for high priority events (interrupts, NMI, BH) at the end of a