[PATCH V2 3/9] New commands `enable probe' and `disable probe'.

Pedro Alves palves@redhat.com
Fri Oct 17 00:43:00 GMT 2014


On 10/17/2014 01:36 AM, Pedro Alves wrote:
> On 10/11/2014 07:39 AM, Jose E. Marchesi wrote:
>>
>> (gdb) info probes
>> Provider Name             Where              Semaphore Enabled Object                         
>> demo     am-main          0x0000000000400c96           n/a     /home/jemarch/oracle/usdt/demo 
>> demo     another          0x0000000000400c8b n/a       always  /home/jemarch/oracle/usdt/demo 
>> demo     progress-counter 0x0000000000400c81 n/a       no      /home/jemarch/oracle/usdt/demo
>>
>> In the example above demo:am-main is a systemtap probe, for which
>> "Enabled" reads n/a.  demo:another is a dtrace probe which cannot be
>> disabled (it does not have any associated enabler) and
>> demo:progress-counter is a dtrace probe which is disabled.
> 
> Shouldn't we explicitly say which probe is stap, vs dprobe (vs whatever
> other probe type)?  Like, either a new column:
> 
> ~~~
> Type    Provider Name             Where              Semaphore Enabled Object
> stap    demo     am-main          0x0000000000400c96           n/a     /home/jemarch/oracle/usdt/demo
> dtrace  demo     another          0x0000000000400c8b n/a       always  /home/jemarch/oracle/usdt/demo
> dtrace  demo     progress-counter 0x0000000000400c81 n/a       no      /home/jemarch/oracle/usdt/demo
> ~~~
> 
> or, sort output by probe type:
> 
> ~~~
> Stap probes:
> 
> Type    Provider Name             Where              Semaphore Enabled Object
> stap    demo     am-main          0x0000000000400c96           n/a     /home/jemarch/oracle/usdt/demo
> 
> Dtrace probes:
> 
> Type    Provider Name             Where              Semaphore Enabled Object
> dtrace  demo     another          0x0000000000400c8b n/a       always  /home/jemarch/oracle/usdt/demo
> dtrace  demo     progress-counter 0x0000000000400c81 n/a       no      /home/jemarch/oracle/usdt/demo
> ~~~

This also raises the question, can't we have both a stap
probe and a dtrace probe with the name provider and name?  Like,
using the proposed output that doesn't distinguish the probe types,
can't the user end up with the confusing:

Provider Name             Where              Semaphore Enabled Object
demo     am-main          0x0000000000400c96           n/a     /home/jemarch/oracle/usdt/demo
demo     am-main          0x0000000000400c8b n/a       always  /home/jemarch/oracle/usdt/demo

Does GDB cope correctly with this?  Will the user have
trouble specifying the probe he wants with the current UI?

Thanks,
Pedro Alves



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