eu-stacktrace [10/12]: use dwflst_tracker_find_pid

Initial minimal change to ensure dwflst_tracker_find_pid is
tested. For now, we keep the additional dwfltab implementation in
stacktrace.c, since it's being used to track statistics.

In future follow-ups, it will be good to switch to storing
eu-stacktrace statistics e.g. in dwfl->process->callbacks_arg. This
requires some additional design to keep the statistics from being lost
when a pid is reused and the corresponding processtracker table entry
is replaced.

* src/stacktrace.c (sysprof_init_dwfl): New function.
  (sysprof_find_dwfl): Rename the existing sysprof_init_dwfl.
  Also use dwflst_tracker_find_pid with callback.
  (sysprof_unwind_cb): Rename the existing sysprof_init_dwfl.

Signed-off-by: Serhei Makarov <serhei@serhei.io>

diff --git a/src/stacktrace.c b/src/stacktrace.c
index c0c9929dcaa0210354b6a6ddf3e169b3e2f6defa..9a6b7601ff22a4e5f7a7c15f28c6bc1a28a597ea 100644 (file)
--- a/src/stacktrace.c
+++ b/src/stacktrace.c
@@ -96,7 +96,7 @@
 #include ELFUTILS_HEADER(ebl)
 /* #include ELFUTILS_HEADER(dwfl) */
 #include "../libdwfl/libdwflP.h"
-/* XXX: Private header needed for find_procfile, sysprof_init_dwfl,
+/* XXX: Private header needed for find_procfile, sysprof_find_dwfl,
    sample_set_initial_registers. */
 #include ELFUTILS_HEADER(dwfl_stacktrace)
 
@@ -1014,7 +1014,34 @@ find_procfile (Dwfl *dwfl, pid_t *pid, Elf **elf, int *elf_fd)
 }
 
 Dwfl *
-sysprof_init_dwfl (struct sysprof_unwind_info *sui,
+sysprof_init_dwfl_cb (Dwflst_Process_Tracker *cb_tracker,
+                     pid_t pid,
+                     void *arg __attribute__ ((unused)))
+{
+  Dwfl *dwfl = dwflst_tracker_dwfl_begin (cb_tracker);
+
+  int err = dwfl_linux_proc_report (dwfl, pid);
+  if (err < 0)
+    {
+      if (show_failures)
+       fprintf(stderr, "dwfl_linux_proc_report pid %lld: %s",
+               (long long) pid, dwfl_errmsg (-1));
+      return NULL;
+    }
+  err = dwfl_report_end (dwfl, NULL, NULL);
+  if (err != 0)
+    {
+      if (show_failures)
+       fprintf(stderr, "dwfl_report_end pid %lld: %s",
+               (long long) pid, dwfl_errmsg (-1));
+      return NULL;
+    }
+
+  return dwfl;
+}
+
+Dwfl *
+sysprof_find_dwfl (struct sysprof_unwind_info *sui,
                   SysprofCaptureStackUser *ev,
                   SysprofCaptureUserRegs *regs)
 {
@@ -1027,42 +1054,24 @@ sysprof_init_dwfl (struct sysprof_unwind_info *sui,
   if (regs->n_regs < EXPECTED_REGS) /* XXX expecting everything except FLAGS */
     {
       if (show_failures)
-       fprintf(stderr, N_("sysprof_init_dwfl: n_regs=%d, expected %d\n"),
+       fprintf(stderr, N_("sysprof_find_dwfl: n_regs=%d, expected %d\n"),
                regs->n_regs, EXPECTED_REGS);
       return NULL;
     }
 
-  Dwfl *dwfl = pid_find_dwfl(pid);
   struct __sample_arg *sample_arg;
+  Dwfl *dwfl = dwflst_tracker_find_pid (tracker, pid, sysprof_init_dwfl_cb, NULL);
   bool cached = false;
-  if (dwfl != NULL)
+  if (dwfl != NULL && dwfl->process != NULL)
     {
       sample_arg = dwfl->process->callbacks_arg; /* XXX requires libdwflP.h */
       cached = true;
       goto reuse;
     }
-  dwfl = dwflst_tracker_dwfl_begin (tracker);
-
-  int err = dwfl_linux_proc_report (dwfl, pid);
-  if (err < 0)
-    {
-      if (show_failures)
-       fprintf(stderr, "dwfl_linux_proc_report pid %lld: %s",
-               (long long) pid, dwfl_errmsg (-1));
-      return NULL;
-    }
-  err = dwfl_report_end (dwfl, NULL, NULL);
-  if (err != 0)
-    {
-      if (show_failures)
-       fprintf(stderr, "dwfl_report_end pid %lld: %s",
-               (long long) pid, dwfl_errmsg (-1));
-      return NULL;
-    }
 
   Elf *elf = NULL;
   int elf_fd = -1;
-  err = find_procfile (dwfl, &pid, &elf, &elf_fd);
+  int err = find_procfile (dwfl, &pid, &elf, &elf_fd);
   if (err < 0)
     {
       if (show_failures)
@@ -1099,7 +1108,7 @@ sysprof_init_dwfl (struct sysprof_unwind_info *sui,
 
   if (show_frames) {
     bool is_abi32 = (sample_arg->abi == PERF_SAMPLE_REGS_ABI_32);
-    fprintf(stderr, "sysprof_init_dwfl pid %lld%s: size=%ld%s pc=%lx sp=%lx+(%lx)\n",
+    fprintf(stderr, "sysprof_find_dwfl pid %lld%s: size=%ld%s pc=%lx sp=%lx+(%lx)\n",
            (long long) pid, cached ? " (cached)" : "",
            sample_arg->size, is_abi32 ? " (32-bit)" : "",
            sample_arg->pc, sample_arg->base_addr,
@@ -1260,7 +1269,7 @@ sysprof_unwind_cb (SysprofCaptureFrame *frame, void *arg)
   SysprofCaptureUserRegs *regs = (SysprofCaptureUserRegs *)tail_ptr;
   if (show_frames)
     fprintf(stderr, "\n"); /* extra newline for padding */
-  Dwfl *dwfl = sysprof_init_dwfl (sui, ev, regs);
+  Dwfl *dwfl = sysprof_find_dwfl (sui, ev, regs);
   if (dwfl == NULL)
     {
       if (show_summary)
@@ -1270,7 +1279,7 @@ sysprof_unwind_cb (SysprofCaptureFrame *frame, void *arg)
          dwfl_ent->lost_samples++;
        }
       if (show_failures)
-       fprintf(stderr, "sysprof_init_dwfl pid %lld (%s) (failed)\n",
+       fprintf(stderr, "sysprof_find_dwfl pid %lld (%s) (failed)\n",
                (long long)frame->pid, comm);
       return SYSPROF_CB_OK;
     }