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.
