From: compudj <compudj@04897980-b3bd-0310-b5e0-8ef037075253>
Date: Fri, 23 Feb 2007 15:57:26 +0000 (+0000)
Subject: discuss marker types
X-Git-Tag: v0.12.20~1094
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=5a1e0e3f54f92a41503f427777eb105a04a48082;p=lttv.git

discuss marker types

git-svn-id: http://ltt.polymtl.ca/svn@2395 04897980-b3bd-0310-b5e0-8ef037075253
---

diff --git a/ltt/branches/poly/doc/developer/marker-types.txt b/ltt/branches/poly/doc/developer/marker-types.txt
new file mode 100644
index 00000000..4c3b6c11
--- /dev/null
+++ b/ltt/branches/poly/doc/developer/marker-types.txt
@@ -0,0 +1,76 @@
+
+#define MARK_TRAP 1
+#define _MARK_TRAP (1 << MARK_TRAP)
+  Can generate a trap
+
+#define MARK_PREEMPT 2
+#define _MARK_PREEMPT (1 << MARK_PREEMPT)
+  Permits blocking calls within probe.
+  How to deal with probe removal :
+  Each site has its per cpu probe_exec counters. The sum of the signed values
+  gives the number of executors. Operations inc/dec on those values are done
+  within preempt disable so they can be done non atomically without risking
+  to be corrupted by another CPU.
+  1 - disable site and remove call
+  2 - while sum of probe_exec counters != 0, sleep 50ms
+      fail after 10 loops
+        - if someone sleeps in here for a long time or waits for 
+	  a busy ressource, removal may fail with -EBUSY.
+
+site :
+
+if (enable) {
+	preempt_disable();
+	probe_exec[smp_processor_id()]++;
+	preempt_enable();
+	handler();
+	preempt_disable();
+	probe_exec[smp_processor_id()]--;
+	preempt_enable();
+}
+
+#define MARK_RESCHED 3
+#define _MARK_RESCHED (1 << MARK_RESCHED)
+  preempt_schedule() will be called by the marker.
+
+#define _MARK_DEFAULT (~_MARK_PREEMPT | _MARK_TRAP | _MARK_RESCHED)
+
+#define MARK (format, ...) MARK_OPTIONS(MARK_DEFAULT, format, __VA_ARGS__)
+
+ex. i386
+#define MARK_OPTIONS(opt, format, ...) \
+{ \
+	if (opt & _MARK_NO_TRAP) \
+		GEN_MARK(opt, format, __VA_ARGS__); \
+	else \
+		MARK(opt, format, __VA_ARGS__); \
+}
+
+ex. powerpc
+#define MARK_OPTIONS(opt, format, ...) MARK(opt, format, __VA_ARGS__);
+
+
+MARK(opt, format, ...) \
+static declare opt in struct; \
+if (enable) {
+	preempt_disable();
+	if (opt & _MARK_PREEMPT) {
+		probe_exec[smp_processor_id()]++;
+		if (opt & _MARK_RESCHED)
+			preempt_enable();
+		else
+			preempt_enable_no_resched();
+	}
+	handler();
+	if (opt & _MARK_PREEMPT) {
+		preempt_disable();
+		probe_exec[smp_processor_id()]--;
+	}
+	if (opt & _MARK_RESCHED)
+		preempt_enable();
+	else
+		preempt_enable_no_resched();
+}
+
+
+