trace2/tr2_sid.c

   1 #include "cache.h"
   2 #include "trace2/tr2_sid.h"
   3
   4 #define TR2_ENVVAR_PARENT_SID "GIT_TR2_PARENT_SID"
   5
   6 static struct strbuf tr2sid_buf = STRBUF_INIT;
   7 static int tr2sid_nr_git_parents;
   8
   9 /*
  10  * Compute a "unique" session id (SID) for the current process.  This allows
  11  * all events from this process to have a single label (much like a PID).
  12  *
  13  * Export this into our environment so that all child processes inherit it.
  14  *
  15  * If we were started by another git instance, use our parent's SID as a
  16  * prefix.  (This lets us track parent/child relationships even if there
  17  * is an intermediate shell process.)
  18  *
  19  * Additionally, count the number of nested git processes.
  20  */
  21 static void tr2_sid_compute(void)
  22 {
  23         uint64_t us_now;
  24         const char *parent_sid;
  25
  26         if (tr2sid_buf.len)
  27                 return;
  28
  29         parent_sid = getenv(TR2_ENVVAR_PARENT_SID);
  30         if (parent_sid && *parent_sid) {
  31                 const char *p;
  32                 for (p = parent_sid; *p; p++)
  33                         if (*p == '/')
  34                                 tr2sid_nr_git_parents++;
  35
  36                 strbuf_addstr(&tr2sid_buf, parent_sid);
  37                 strbuf_addch(&tr2sid_buf, '/');
  38                 tr2sid_nr_git_parents++;
  39         }
  40
  41         us_now = getnanotime() / 1000;
  42         strbuf_addf(&tr2sid_buf, "%" PRIuMAX "-%" PRIdMAX, (uintmax_t)us_now,
  43                     (intmax_t)getpid());
  44
  45         setenv(TR2_ENVVAR_PARENT_SID, tr2sid_buf.buf, 1);
  46 }
  47
  48 const char *tr2_sid_get(void)
  49 {
  50         if (!tr2sid_buf.len)
  51                 tr2_sid_compute();
  52
  53         return tr2sid_buf.buf;
  54 }
  55
  56 int tr2_sid_depth(void)
  57 {
  58         if (!tr2sid_buf.len)
  59                 tr2_sid_compute();
  60
  61         return tr2sid_nr_git_parents;
  62 }
  63
  64 void tr2_sid_release(void)
  65 {
  66         strbuf_release(&tr2sid_buf);
  67 }