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-rw-r--r--trace2/tr2_sid.c67
1 files changed, 67 insertions, 0 deletions
diff --git a/trace2/tr2_sid.c b/trace2/tr2_sid.c
new file mode 100644
index 0000000000..984524a43c
--- /dev/null
+++ b/trace2/tr2_sid.c
@@ -0,0 +1,67 @@
+#include "cache.h"
+#include "trace2/tr2_sid.h"
+
+#define TR2_ENVVAR_PARENT_SID "GIT_TR2_PARENT_SID"
+
+static struct strbuf tr2sid_buf = STRBUF_INIT;
+static int tr2sid_nr_git_parents;
+
+/*
+ * Compute a "unique" session id (SID) for the current process. This allows
+ * all events from this process to have a single label (much like a PID).
+ *
+ * Export this into our environment so that all child processes inherit it.
+ *
+ * If we were started by another git instance, use our parent's SID as a
+ * prefix. (This lets us track parent/child relationships even if there
+ * is an intermediate shell process.)
+ *
+ * Additionally, count the number of nested git processes.
+ */
+static void tr2_sid_compute(void)
+{
+ uint64_t us_now;
+ const char *parent_sid;
+
+ if (tr2sid_buf.len)
+ return;
+
+ parent_sid = getenv(TR2_ENVVAR_PARENT_SID);
+ if (parent_sid && *parent_sid) {
+ const char *p;
+ for (p = parent_sid; *p; p++)
+ if (*p == '/')
+ tr2sid_nr_git_parents++;
+
+ strbuf_addstr(&tr2sid_buf, parent_sid);
+ strbuf_addch(&tr2sid_buf, '/');
+ tr2sid_nr_git_parents++;
+ }
+
+ us_now = getnanotime() / 1000;
+ strbuf_addf(&tr2sid_buf, "%" PRIuMAX "-%" PRIdMAX, (uintmax_t)us_now,
+ (intmax_t)getpid());
+
+ setenv(TR2_ENVVAR_PARENT_SID, tr2sid_buf.buf, 1);
+}
+
+const char *tr2_sid_get(void)
+{
+ if (!tr2sid_buf.len)
+ tr2_sid_compute();
+
+ return tr2sid_buf.buf;
+}
+
+int tr2_sid_depth(void)
+{
+ if (!tr2sid_buf.len)
+ tr2_sid_compute();
+
+ return tr2sid_nr_git_parents;
+}
+
+void tr2_sid_release(void)
+{
+ strbuf_release(&tr2sid_buf);
+}