Re: [PATCH 11/12] Use reinsert_breakpoint for vCont;s

[Yao Qi <qiyaoltc@gmail.com>]

Pedro Alves <palves@redhat.com> writes:

>> @@ -4293,7 +4313,7 @@ linux_resume_one_lwp_throw (struct lwp_info *lwp,
>>  
>>        step = maybe_hw_step (thread);
>>      }
>> -  else
>> +  else if (lwp->resume != NULL && lwp->resume->kind != resume_step)
>>      {
>>        /* If the thread isn't doing step-over, there shouldn't be any
>>  	 reinsert breakpoints.  */
>
> Consider (non-stop RSP):
>
>  -> vCont;s:1
>  <- OK
>  -> vCont;s:2
>  <- OK
>
> The handling of the second vCont sets thread 1's lwp->resume to NULL.

If so, the assert won't be called for thread 1.

> The lwp->resume pointer is only meaningful within linux_resume
> and its callees.  (But this function is called in other contexts.)
>

When I wrote the patch, it took me a while to think about this condition
check.  I wanted to remove this condition and assert, but finally
decided to leave it there, as it is not harmful.  If lwp->resume is only
meaningful within linux_resume and its callees, how about remove the
condition check and assert here?

>> @@ -5009,12 +5033,52 @@ linux_resume (struct thread_resume *resume_info, size_t n)
>>  	debug_printf ("Resuming, no pending status or step over needed\n");
>>      }
>>  
>> +  /* Before we resume the threads, if resume_step is requested by GDB,
>> +     stop all threads and install reinsert breakpoints.  */
>
> Looking again, I think the rationale for stopping threads should
> be mentioned here, as it's not obvious.
>

How about this,

  /* Before we resume the threads, if resume_step is requested by GDB,
     we need to access the inferior memory to install reinsert
     breakpoints, so stop all threads.  */

>> @@ -5110,7 +5174,8 @@ proceed_one_lwp (struct inferior_list_entry *entry, void *except)
>>        if (debug_threads)
>>  	debug_printf ("   stepping LWP %ld, client wants it stepping\n",
>>  		      lwpid_of (thread));
>> -      step = 1;
>> +
>> +      step = maybe_hw_step (thread);
>>      }
>>    else if (lwp->bp_reinsert != 0)
>>      {
>> @@ -5176,6 +5241,30 @@ proceed_all_lwps (void)
>>    if (debug_threads)
>>      debug_printf ("Proceeding, no step-over needed\n");
>>  
>> +  /* Re-install the reinsert breakpoints on software single step target
>> +     if the client wants it step.  */
>> +  if (can_software_single_step ())
>
> Not immediately obvious to why is this necessary.  Where were they
> removed in the first place?  I'm it must be necessary, but maybe
> extending the comment helps.

How about this

  /* On software single step target, we removed reinsert breakpoints
     after we get any events from the inferior.  If the client wants
     thread step, re-install these reinsert breakpoints.  */

-- 
Yao (齐尧)