RE: [PATCH 4/8] gdb, infrun: refactor part of `proceed` into separate function

[Andrew Burgess <aburgess@redhat.com>]

"Aktemur, Tankut Baris" <tankut.baris.aktemur@intel.com> writes:

> On Thursday, June 22, 2023 3:17 PM, Andrew Burgess wrote:
>> From: Mihails Strasuns <mihails.strasuns@intel.com>
>> 
>> Split the thread resuming code from proceed into new function
>> proceed_resume_thread_checked.
>> 
>> Co-Authored-By: Christina Schimpe <christina.schimpe@intel.com>
>> ---
>>  gdb/infrun.c | 148 +++++++++++++++++++++++++++------------------------
>>  1 file changed, 79 insertions(+), 69 deletions(-)
>> 
>> diff --git a/gdb/infrun.c b/gdb/infrun.c
>> index 5b0257076f0..b10b7c59652 100644
>> --- a/gdb/infrun.c
>> +++ b/gdb/infrun.c
>> @@ -3268,6 +3268,82 @@ check_multi_target_resumption (process_stratum_target *resume_target)
>>      }
>>  }
>> 
>> +/* Helper function for `proceed`.  Check if thread TP is suitable for
>> +   resuming, and, if it is, switch to the thread and call
>> +   `keep_going_pass_signal`.  If TP is not suitable for resuming then this
>> +   function will just return without switching threads.  */
>> +
>> +static void
>> +proceed_resume_thread_checked (thread_info *tp)
>> +{
>> +  if (!tp->inf->has_execution ())
>> +    {
>> +      infrun_debug_printf ("[%s] target has no execution",
>> +			   tp->ptid.to_string ().c_str ());
>> +      return;
>> +    }
>> +
>> +  if (tp->resumed ())
>> +    {
>> +      infrun_debug_printf ("[%s] resumed",
>> +			   tp->ptid.to_string ().c_str ());
>> +      gdb_assert (tp->executing () || tp->has_pending_waitstatus ());
>> +      return;
>> +    }
>> +
>> +  if (thread_is_in_step_over_chain (tp))
>> +    {
>> +      infrun_debug_printf ("[%s] needs step-over",
>> +			   tp->ptid.to_string ().c_str ());
>> +      return;
>> +    }
>> +
>> +  /* When handling a vfork GDB removes all breakpoints from the program
>> +     space in which the vfork is being handled, as such we must take care
>> +     not to resume any thread other than the vfork parent -- resuming the
>> +     vfork parent allows GDB to receive and handle the 'vfork done'
>> +     event.  */
>> +  if (tp->inf->thread_waiting_for_vfork_done != nullptr)
>> +    {
>> +      if (target_is_non_stop_p ())
>> +	{
>> +	  /* For non-stop targets, regardless of whether GDB is using
>> +	     all-stop or non-stop mode, threads are controlled
>> +	     individually.
>> +
>> +	     When a thread is handling a vfork, breakpoints are removed
>> +	     from the inferior (well, program space in fact), so it is
>> +	     critical that we don't try to resume any thread other than the
>> +	     vfork parent.  */
>> +	  if (tp != tp->inf->thread_waiting_for_vfork_done)
>> +	    {
>> +	      infrun_debug_printf ("[%s] thread %s of this inferior is "
>> +				   "waiting for vfork-done",
>> +				   tp->ptid.to_string ().c_str (),
>> +				   tp->inf->thread_waiting_for_vfork_done
>> +				     ->ptid.to_string ().c_str ());
>> +	      return;
>> +	    }
>> +	}
>> +      else
>> +	{
>> +	  /* For all-stop targets, when we attempt to resume the inferior,
>> +	     we will in fact only resume the vfork parent thread, this is
>> +	     handled in internal_resume_ptid, as such, there is nothing
>> +	     more that needs doing here.  */
>
> I wonder if here we should do
>
>     gdb_assert (tp == tp->inf->thread_waiting_for_vfork_done);
>

That's a good idea.  I've also updated the comment within this else
block as the current text doesn't really cover why this assert holds.

I've posted a V2 with this change.

Thanks,
Andrew

> -Baris
>
>> +	}
>> +    }
>> +
>> +  infrun_debug_printf ("resuming %s",
>> +		       tp->ptid.to_string ().c_str ());
>> +
>> +  execution_control_state ecs (tp);
>> +  switch_to_thread (tp);
>> +  keep_going_pass_signal (&ecs);
>> +  if (!ecs.wait_some_more)
>> +    error (_("Command aborted."));
>> +}
>> +
>>  /* Basic routine for continuing the program in various fashions.
>> 
>>     ADDR is the address to resume at, or -1 for resume where stopped.
>> @@ -3456,77 +3532,11 @@ proceed (CORE_ADDR addr, enum gdb_signal siggnal)
>>  						       resume_ptid))
>>  	  {
>>  	    switch_to_thread_no_regs (tp);
>> -
>> -	    if (!tp->inf->has_execution ())
>> -	      {
>> -		infrun_debug_printf ("[%s] target has no execution",
>> -				     tp->ptid.to_string ().c_str ());
>> -		continue;
>> -	      }
>> -
>> -	    if (tp->resumed ())
>> -	      {
>> -		infrun_debug_printf ("[%s] resumed",
>> -				     tp->ptid.to_string ().c_str ());
>> -		gdb_assert (tp->executing () || tp->has_pending_waitstatus ());
>> -		continue;
>> -	      }
>> -
>> -	    if (thread_is_in_step_over_chain (tp))
>> -	      {
>> -		infrun_debug_printf ("[%s] needs step-over",
>> -				     tp->ptid.to_string ().c_str ());
>> -		continue;
>> -	      }
>> -
>> -	    /* If a thread of that inferior is waiting for a vfork-done
>> -	       (for a detached vfork child to exec or exit), breakpoints are
>> -	       removed.  We must not resume any thread of that inferior, other
>> -	       than the one waiting for the vfork-done.  */
>> -	    if (tp->inf->thread_waiting_for_vfork_done != nullptr
>> -		&& tp != tp->inf->thread_waiting_for_vfork_done)
>> -	      {
>> -		infrun_debug_printf ("[%s] another thread of this inferior is "
>> -				     "waiting for vfork-done",
>> -				     tp->ptid.to_string ().c_str ());
>> -		continue;
>> -	      }
>> -
>> -	    infrun_debug_printf ("resuming %s",
>> -				 tp->ptid.to_string ().c_str ());
>> -
>> -	    execution_control_state ecs (tp);
>> -	    switch_to_thread (tp);
>> -	    keep_going_pass_signal (&ecs);
>> -	    if (!ecs.wait_some_more)
>> -	      error (_("Command aborted."));
>> -	  }
>> -      }
>> -    else if (!cur_thr->resumed ()
>> -	     && !thread_is_in_step_over_chain (cur_thr))
>> -      {
>> -	/* In non-stop mode, if a there exists a thread waiting for a vfork
>> -	   then only allow that thread to resume (breakpoints are removed
>> -	   from an inferior when handling a vfork).
>> -
>> -	   We check target_is_non_stop_p here rather than just checking the
>> -	   non-stop flag, though these are equivalent (all-stop on a
>> -	   non-stop target was handled in a previous block, so at this
>> -	   point, if target_is_non_stop_p then GDB must be running on
>> -	   non-stop mode).  By using target_is_non_stop_p it will be easier
>> -	   to merge this block with the previous in a later commit.  */
>> -	if (!(target_is_non_stop_p ()
>> -	      && cur_thr->inf->thread_waiting_for_vfork_done != nullptr
>> -	      && cur_thr->inf->thread_waiting_for_vfork_done != cur_thr))
>> -	  {
>> -	    /* The thread wasn't started, and isn't queued, run it now.  */
>> -	    execution_control_state ecs (cur_thr);
>> -	    switch_to_thread (cur_thr);
>> -	    keep_going_pass_signal (&ecs);
>> -	    if (!ecs.wait_some_more)
>> -	      error (_("Command aborted."));
>> +	    proceed_resume_thread_checked (tp);
>>  	  }
>>        }
>> +    else
>> +      proceed_resume_thread_checked (cur_thr);
>> 
>>      disable_commit_resumed.reset_and_commit ();
>>    }
>> --
>> 2.25.4
>
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