On Mon, Nov 11, 2013 at 11:09:46AM +0000, Vijay Kilari wrote:
On Fri, Nov 8, 2013 at 7:48 PM, Will Deacon will.deacon@arm.com wrote:
On Tue, Nov 05, 2013 at 08:45:45AM +0000, vijay.kilari@gmail.com wrote:
@@ -153,6 +166,8 @@ int kgdb_arch_handle_exception(int exception_vector, int signo, * Packet D (Detach), k (kill). No special handling * is required here */
atomic_set(&kgdb_cpu_doing_single_step, -1);kgdb_single_step = 0;This looks really weird: you have two variables, which you attempt to keep in sync, only one of them is an atomic access and you don't have any locking or memory barriers between them, so it must be ok if they're not in-sync. In which case, why do we have two variables?
IMHO, two variables are being used by kgdb framework The variables 'kgdb_cpu_doing_single_step' holds the cpu on which step debugging is happening. With this, when during step debugging, it ensures that on next step debug exception only this CPU aquires master lock and step debugging is performed.
The variable 'kgdb_single_step' is used to know if step debugging is ongoing or not. If so, the non-primary cpu's are not released untill the continue command is received So, with this the cpu's are not released and acquired for every step command
Ok, but in what situation would you have both kgdb_cpu_doing_single_step == -1 and kgdb_single_step == 1 (ignoring races between setting the two variables)?
In other words, can we reduce this to a single variable?
Will