Slightly tweak and clarify target_resume's interface

The current target_resume interface is a bit odd & non-intuitive.
I've found myself explaining it a couple times the recent past, while
reviewing patches that assumed STEP/SIGNAL always applied to the
passed in PTID.  It goes like this today:

  - if the passed in PTID is a thread, then the step/signal request is
    for that thread.

  - otherwise, if PTID is a wildcard (all threads or all threads of
    process), the step/signal request is for inferior_ptid, and PTID
    indicates which set of threads run free.

Because GDB always switches the current thread to "leader" thread
being resumed/stepped/signalled, we can simplify this a bit to:

  - step/signal are always for inferior_ptid.

  - PTID indicates the set of threads that run free.

Still not ideal, but it's a minimal change and at least there are no
special cases this way.

That's what this patch does.  It renames the PTID parameter to
SCOPE_PTID, adds some assertions to target_resume, and tweaks
target_resume's description.  In addition, it also renames PTID to
SCOPE_PTID in the remote and linux-nat targets, and simplifies their
implementation a little bit.  Other targets could do the same, but
they don't have to.

Change-Id: I02a2ec2ab3a3e9b191de1e9a84f55c17cab7daaf

1 files changed, 10 insertions, 19 deletions

diff --git a/gdb/linux-nat.c b/gdb/linux-nat.c
index dff8d07..740cc0d 100644
--- a/gdb/linux-nat.c
+++ b/gdb/linux-nat.c
@@ -1595,32 +1595,22 @@ resume_set_callback (struct lwp_info *lp)
 }
 
 void
-linux_nat_target::resume (ptid_t ptid, int step, enum gdb_signal signo)
+linux_nat_target::resume (ptid_t scope_ptid, int step, enum gdb_signal signo)
 {
   struct lwp_info *lp;
-  int resume_many;
 
   linux_nat_debug_printf ("Preparing to %s %s, %s, inferior_ptid %s",
 			  step ? "step" : "resume",
-			  ptid.to_string ().c_str (),
+			  scope_ptid.to_string ().c_str (),
 			  (signo != GDB_SIGNAL_0
 			   ? strsignal (gdb_signal_to_host (signo)) : "0"),
 			  inferior_ptid.to_string ().c_str ());
 
-  /* A specific PTID means `step only this process id'.  */
-  resume_many = (minus_one_ptid == ptid
-		 || ptid.is_pid ());
-
   /* Mark the lwps we're resuming as resumed and update their
      last_resume_kind to resume_continue.  */
-  iterate_over_lwps (ptid, resume_set_callback);
+  iterate_over_lwps (scope_ptid, resume_set_callback);
 
-  /* See if it's the current inferior that should be handled
-     specially.  */
-  if (resume_many)
-    lp = find_lwp_pid (inferior_ptid);
-  else
-    lp = find_lwp_pid (ptid);
+  lp = find_lwp_pid (inferior_ptid);
   gdb_assert (lp != NULL);
 
   /* Remember if we're stepping.  */
@@ -1669,11 +1659,12 @@ linux_nat_target::resume (ptid_t ptid, int step, enum gdb_signal signo)
       return;
     }
 
-  if (resume_many)
-    iterate_over_lwps (ptid, [=] (struct lwp_info *info)
-			     {
-			       return linux_nat_resume_callback (info, lp);
-			     });
+  /* No use iterating unless we're resuming other threads.  */
+  if (scope_ptid != lp->ptid)
+    iterate_over_lwps (scope_ptid, [=] (struct lwp_info *info)
+      {
+	return linux_nat_resume_callback (info, lp);
+      });
 
   linux_nat_debug_printf ("%s %s, %s (resume event thread)",
 			  step ? "PTRACE_SINGLESTEP" : "PTRACE_CONT",