Re: [Qemu-devel] [PATCH v6 07/16] gdbstub: add multiprocess support to (f|s)ThreadInfo and ThreadExtraInfo

[Luc Michel <luc.michel@greensocs.com>]

On 11/16/18 11:04 AM, Edgar E. Iglesias wrote:
> On Thu, Nov 15, 2018 at 10:41:58AM +0100, Luc Michel wrote:
>> Change the thread info related packets handling to support multiprocess
>> extension.
>>
>> Add the CPUs class name in the extra info to help differentiate
>> them in multiprocess mode.
>>
>> Signed-off-by: Luc Michel <luc.michel@greensocs.com>
>> Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
>> ---
>>  gdbstub.c | 35 +++++++++++++++++++++++++----------
>>  1 file changed, 25 insertions(+), 10 deletions(-)
>>
>> diff --git a/gdbstub.c b/gdbstub.c
>> index d19b0137e8..292dee8914 100644
>> --- a/gdbstub.c
>> +++ b/gdbstub.c
>> @@ -1260,11 +1260,10 @@ out:
>>  static int gdb_handle_packet(GDBState *s, const char *line_buf)
>>  {
>>      CPUState *cpu;
>>      CPUClass *cc;
>>      const char *p;
>> -    uint32_t thread;
>>      uint32_t pid, tid;
>>      int ch, reg_size, type, res;
>>      uint8_t mem_buf[MAX_PACKET_LENGTH];
>>      char buf[sizeof(mem_buf) + 1 /* trailing NUL */];
>>      char thread_id[16];
>> @@ -1556,30 +1555,46 @@ static int gdb_handle_packet(GDBState *s, const char *line_buf)
>>              snprintf(buf, sizeof(buf), "QC%s",
>>                       gdb_fmt_thread_id(s, cpu, thread_id, sizeof(thread_id)));
>>              put_packet(s, buf);
>>              break;
>>          } else if (strcmp(p,"fThreadInfo") == 0) {
>> -            s->query_cpu = first_cpu;
>> +            s->query_cpu = gdb_first_cpu(s);
>>              goto report_cpuinfo;
>>          } else if (strcmp(p,"sThreadInfo") == 0) {
>>          report_cpuinfo:
>>              if (s->query_cpu) {
>> -                snprintf(buf, sizeof(buf), "m%x", cpu_gdb_index(s->query_cpu));
>> +                snprintf(buf, sizeof(buf), "m%s",
>> +                         gdb_fmt_thread_id(s, s->query_cpu,
>> +                                       thread_id, sizeof(thread_id)));
>>                  put_packet(s, buf);
>> -                s->query_cpu = CPU_NEXT(s->query_cpu);
>> +                s->query_cpu = gdb_next_cpu(s, s->query_cpu);
>>              } else
>>                  put_packet(s, "l");
>>              break;
>>          } else if (strncmp(p,"ThreadExtraInfo,", 16) == 0) {
>> -            thread = strtoull(p+16, (char **)&p, 16);
>> -            cpu = find_cpu(thread);
>> +            if (read_thread_id(p + 16, &p, &pid, &tid) == GDB_READ_THREAD_ERR) {
>> +                put_packet(s, "E22");
>> +                break;
>> +            }
>> +            cpu = gdb_get_cpu(s, pid, tid);
>>              if (cpu != NULL) {
>>                  cpu_synchronize_state(cpu);
>> -                /* memtohex() doubles the required space */
>> -                len = snprintf((char *)mem_buf, sizeof(buf) / 2,
>> -                               "CPU#%d [%s]", cpu->cpu_index,
>> -                               cpu->halted ? "halted " : "running");
>> +
>> +                if (s->multiprocess && (s->process_num > 1)) {
>> +                    /* Print the CPU model in multiprocess mode */
>> +                    ObjectClass *oc = object_get_class(OBJECT(cpu));
>> +                    const char *cpu_model = object_class_get_name(oc);
>> +                    len = snprintf((char *)mem_buf, sizeof(buf) / 2,
>> +                                   "CPU#%d %s [%s]", cpu->cpu_index,
>> +                                   cpu_model,
>> +                                   cpu->halted ? "halted " : "running");
> 
> 
> 
> I wonder if we could also print a friendly name here deducted from QOM?
> In some of our use-cases we have an array of MicroBlazes that all live
> in different HW subsystems and are named differently (e.g CSU, PMU, PMC,
> PSM etc).
> 
> Instead of just seeing a list of MicroBlaze cores it may be more useful
> to see the actual core name of some sort, e.g:
> 
> Instead of:
> CPU#0 MicroBlaze [running]
> CPU#1 MicroBlaze [running]
> CPU#2 MicroBlaze [running]
> CPU#3 MicroBlaze [running]
> 
> Perhaps something like:
> CPU#0 MicroBlaze PMU [running]
> CPU#1 MicroBlaze PMC-PPU0 [running]
> CPU#2 MicroBlaze PMC-PPU1 [running]
> CPU#3 MicroBlaze PSM [running]
> 
> Any thoughts on that?
I wanted to avoid the ThreadExtraInfo packet to become too much cluttered.

Here are some tests adding the component part of the CPU canonical name:

(gdb) info threads
  Id   Target Id         Frame
  1.1  Thread 1.1 (CPU#0 cortex-a53-arm-cpu apu-cpu[0] [running])
0x0000000000000000 in ?? ()
  1.2  Thread 1.2 (CPU#1 cortex-a53-arm-cpu apu-cpu[1] [halted ])
0x0000000000000000 in ?? ()
  1.3  Thread 1.3 (CPU#2 cortex-a53-arm-cpu apu-cpu[2] [halted ])
0x0000000000000000 in ?? ()
  1.4  Thread 1.4 (CPU#3 cortex-a53-arm-cpu apu-cpu[3] [halted ])
0x0000000000000000 in ?? ()
* 2.1  Thread 2.5 (CPU#4 cortex-r5f-arm-cpu rpu-cpu[0] [halted ])
0xffff0000 in ?? ()
  2.2  Thread 2.6 (CPU#5 cortex-r5f-arm-cpu rpu-cpu[1] [halted ])
0xffff0000 in ?? ()

The model name takes quite some room. The interesting info are `arm` and
`cortex-xxx`, but AFAIK there is no way of extracting that for a CPU
generically.

In this case, having the component part of the canonical name is ok
because self-explanatory. However we could encounter cases where the
parent name would be necessary to discriminate the CPUs, something like:
  cluster[0]/cpu[0]
            /cpu[1]
  cluster[1]/cpu[0]
            /cpu[1]
  ...

The "safest" way would be to have the whole path:

(gdb) info threads
  Id   Target Id         Frame
  1.1  Thread 1.1 (CPU#0 cortex-a53-arm-cpu
/machine/soc/apu-cluster/apu-cpu[0] [running]) 0x0000000000000000 in ?? ()
  1.2  Thread 1.2 (CPU#1 cortex-a53-arm-cpu
/machine/soc/apu-cluster/apu-cpu[1] [halted ]) 0x0000000000000000 in ?? ()
  1.3  Thread 1.3 (CPU#2 cortex-a53-arm-cpu
/machine/soc/apu-cluster/apu-cpu[2] [halted ]) 0x0000000000000000 in ?? ()
  1.4  Thread 1.4 (CPU#3 cortex-a53-arm-cpu
/machine/soc/apu-cluster/apu-cpu[3] [halted ]) 0x0000000000000000 in ?? ()
* 2.1  Thread 2.5 (CPU#4 cortex-r5f-arm-cpu
/machine/soc/rpu-cluster/rpu-cpu[0] [halted ]) 0xffff0000 in ?? ()
  2.2  Thread 2.6 (CPU#5 cortex-r5f-arm-cpu
/machine/soc/rpu-cluster/rpu-cpu[1] [halted ]) 0xffff0000 in ?? ()

But that becomes really cluttered... We could also remove the CPU model
completely.

What are your thoughts?

Thanks,
Luc

> 
> Thanks,
> Edgar
> 
>> +                } else {
>> +                    /* memtohex() doubles the required space */
>> +                    len = snprintf((char *)mem_buf, sizeof(buf) / 2,
>> +                                   "CPU#%d [%s]", cpu->cpu_index,
>> +                                   cpu->halted ? "halted " : "running");
>> +                }
>>                  trace_gdbstub_op_extra_info((char *)mem_buf);
>>                  memtohex(buf, mem_buf, len);
>>                  put_packet(s, buf);
>>              }
>>              break;
>> -- 
>> 2.19.1
>>