[PATCH] Fix/Update misc comments

[Luis Machado <luis dot machado at linaro dot org>]

While doing some investigation of mine, i noticed a few typos,
inaccuracies and missing information.

I went ahead and updated/improved those.

How does it look?

Regards,
Luis

gdb/ChangeLog:

2020-01-06  Luis Machado  <luis.machado@linaro.org>

	* inf-ptrace.c (inf_ptrace_target::resume): Update comments
	* infrun.c (resume_1): Likewise.
	(handle_inferior_event): Likewise.
	* linux-nat.c (linux_nat_target::resume): Likewise.
	(save_stop_reason): Likewise.
	(linux_nat_filter_event): Likewise.
	* linux-nat.h (struct lwp_info) <stop_pc>, <stop_reason>: Likewise.
---
 gdb/inf-ptrace.c |  4 ++--
 gdb/infrun.c     | 11 ++++++-----
 gdb/linux-nat.c  | 16 +++++++++++-----
 gdb/linux-nat.h  |  4 ++--
 4 files changed, 21 insertions(+), 14 deletions(-)

diff --git a/gdb/inf-ptrace.c b/gdb/inf-ptrace.c
index fd18146efe..e424b9668b 100644
--- a/gdb/inf-ptrace.c
+++ b/gdb/inf-ptrace.c
@@ -354,8 +354,8 @@ inf_ptrace_target::resume (ptid_t ptid, int step, enum gdb_signal signal)
   if (step)
     {
       /* If this system does not support PT_STEP, a higher level
-         function will have called single_step() to transmute the step
-         request into a continue request (by setting breakpoints on
+         function will have called the appropriate functions to transmute the
+	 step request into a continue request (by setting breakpoints on
          all possible successor instructions), so we don't have to
          worry about that here.  */
       request = PT_STEP;
diff --git a/gdb/infrun.c b/gdb/infrun.c
index 7ddd21dd09..14c1e76ac1 100644
--- a/gdb/infrun.c
+++ b/gdb/infrun.c
@@ -2388,8 +2388,8 @@ resume_1 (enum gdb_signal sig)
   if (tp->control.trap_expected || bpstat_should_step ())
     tp->control.may_range_step = 0;
 
-  /* If enabled, step over breakpoints by executing a copy of the
-     instruction at a different address.
+  /* If displaced stepping is enabled, step over breakpoints by executing a
+     copy of the instruction at a different address.
 
      We can't use displaced stepping when we have a signal to deliver;
      the comments for displaced_step_prepare explain why.  The
@@ -2477,7 +2477,7 @@ resume_1 (enum gdb_signal sig)
       && step_over_info_valid_p ())
     {
       /* If we have nested signals or a pending signal is delivered
-	 immediately after a handler returns, might might already have
+	 immediately after a handler returns, might already have
 	 a step-resume breakpoint set on the earlier handler.  We cannot
 	 set another step-resume breakpoint; just continue on until the
 	 original breakpoint is hit.  */
@@ -4928,8 +4928,9 @@ Cannot fill $_exitsignal with the correct signal number.\n"));
       stop_waiting (ecs);
       return;
 
-      /* The following are the only cases in which we keep going;
-         the above cases end in a continue or goto.  */
+      /* The following and TARGET_WAITKIND_THREAD_CREATED are the only
+	 cases in which we keep going. The other cases end in a continue or
+	 goto.  */
     case TARGET_WAITKIND_FORKED:
     case TARGET_WAITKIND_VFORKED:
       /* Check whether the inferior is displaced stepping.  */
diff --git a/gdb/linux-nat.c b/gdb/linux-nat.c
index 465b2acd94..53256d4edb 100644
--- a/gdb/linux-nat.c
+++ b/gdb/linux-nat.c
@@ -1696,7 +1696,8 @@ linux_nat_target::resume (ptid_t ptid, int step, enum gdb_signal signo)
   resume_many = (minus_one_ptid == ptid
 		 || ptid.is_pid ());
 
-  /* Mark the lwps we're resuming as resumed.  */
+  /* Mark the lwps we're resuming as resumed and update their
+     last_resume_kind to resume_continue.  */
   iterate_over_lwps (ptid, resume_set_callback);
 
   /* See if it's the current inferior that should be handled
@@ -2721,7 +2722,7 @@ save_stop_reason (struct lwp_info *lp)
 	    {
 	      /* If we determine the LWP stopped for a SW breakpoint,
 		 trust it.  Particularly don't check watchpoint
-		 registers, because at least on s390, we'd find
+		 registers, because, at least on s390, we'd find
 		 stopped-by-watchpoint as long as there's a watchpoint
 		 set.  */
 	      lp->stop_reason = TARGET_STOPPED_BY_SW_BREAKPOINT;
@@ -2925,7 +2926,7 @@ resumed_callback (struct lwp_info *lp)
 }
 
 /* Check if we should go on and pass this event to common code.
-   Return the affected lwp if we are, or NULL otherwise.  */
+   Return the affected lwp if we should, or NULL otherwise.  */
 
 static struct lwp_info *
 linux_nat_filter_event (int lwpid, int status)
@@ -2976,7 +2977,12 @@ linux_nat_filter_event (int lwpid, int status)
   /* Make sure we don't report an event for the exit of an LWP not in
      our list, i.e. not part of the current process.  This can happen
      if we detach from a program we originally forked and then it
-     exits.  */
+     exits.
+
+     Note the forked children exiting may generate a SIGCHLD to the parent
+     process.  We are still interested in that signal since the parent may
+     have handlers for it, so we don't ignore it.  */
+
   if (!WIFSTOPPED (status) && !lp)
     return NULL;
 
@@ -3118,7 +3124,7 @@ linux_nat_filter_event (int lwpid, int status)
 
   /* Don't report signals that GDB isn't interested in, such as
      signals that are neither printed nor stopped upon.  Stopping all
-     threads can be a bit time-consuming so if we want decent
+     threads can be a bit time-consuming, so if we want decent
      performance with heavily multi-threaded programs, especially when
      they're using a high frequency timer, we'd better avoid it if we
      can.  */
diff --git a/gdb/linux-nat.h b/gdb/linux-nat.h
index 0c1695ad10..2f0eeaf362 100644
--- a/gdb/linux-nat.h
+++ b/gdb/linux-nat.h
@@ -228,7 +228,7 @@ struct lwp_info
 
   /* When 'stopped' is set, this is where the lwp last stopped, with
      decr_pc_after_break already accounted for.  If the LWP is
-     running, and stepping, this is the address at which the lwp was
+     running and stepping, this is the address at which the lwp was
      resumed (that is, it's the previous stop PC).  If the LWP is
      running and not stepping, this is 0.  */
   CORE_ADDR stop_pc;
@@ -237,7 +237,7 @@ struct lwp_info
   int step;
 
   /* The reason the LWP last stopped, if we need to track it
-     (breakpoint, watchpoint, etc.)  */
+     (breakpoint, watchpoint, etc).  */
   enum target_stop_reason stop_reason;
 
   /* On architectures where it is possible to know the data address of
-- 
2.17.1