Jason,

On Mon, Sep 19, 2016 at 05:29:36PM -0500, Jason Wessel wrote:
> 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.

Thank you for the explanation. This convinces me very much.

-Takahiro AKASHI

> Cheers,
> Jason.

------------------------------------------------------------------------------
_______________________________________________
Kgdb-bugreport mailing list
Kgdb-bugreport@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/kgdb-bugreport

Reply via email to