On 09/15/2016 11:32 PM, AKASHI Takahiro wrote:
@@ -176,18 +183,14 @@ int kgdb_arch_handle_exception(int exception_vector, int 
                 * 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?


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.


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