On 09/15/2016 11:32 PM, AKASHI Takahiro wrote:
> @@ -176,18 +183,14 @@ int kgdb_arch_handle_exception(int exception_vector, 
> int signo,
>>>              * over and over again.
>>>              */
>>>             kgdb_arch_update_addr(linux_regs, remcom_in_buffer);
>>> -           atomic_set(&kgdb_cpu_doing_single_step, -1);
>>> -           kgdb_single_step =  0;
>>
>> This is a subtle change, but I assume it is what you intended?  All the CPUs 
>> will get released into the run state when exiting the kgdb exception handler.
> You are talking about "- kgdb_single_step = 0." Right?


Correct.

> Do you think that there is any (negative) side effect of this change?


Not at all.   The kernel debugger always skids to a stop, and it is more 
reliable from a locking perspective if the other CPU threads are released while 
a single CPU is asked to single step until the next "skid" for all the other 
CPUs.

When you do not release the other CPUs you can end up single stepping a CPU 
which dead locks or never exits a lock elsewhere due to what ever it was 
blocking on never getting freed from another CPU.

Cheers,
Jason.

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