Re: [PATCH tip/core/rcu 6/8] rcutorture: Print symbolic name for ->gp_state

Josh Triplett
2015-12-05T01:04:28Z

On Fri, Dec 04, 2015 at 04:23:50PM -0800, Paul E. McKenney wrote:
> Currently, ->gp_state is printed as an integer, which slows debugging.
> This commit therefore prints a symbolic name in addition to the integer.
>
> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> [ Updated to fix relational operator called out by Dan Carpenter. ]
> ---
> kernel/rcu/tree.c | 15 +++++++++++++--
> kernel/rcu/tree.h | 9 +++++++++
> 2 files changed, 22 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index 7b78c88e19a3..491c99a73996 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -1187,6 +1187,16 @@ static void record_gp_stall_check_time(struct rcu_state *rsp)
> }
>
> /*
> + * Convert a ->gp_state value to a character string.
> + */
> +static char *gp_state_getname(short gs)

Same comment about "const char *"

> +{
> + if (gs < 0 || gs >= ARRAY_SIZE(gp_state_names))
> + return "???";
> + return gp_state_names[gs];
> +}
> +
> +/*
> * Complain about starvation of grace-period kthread.
> */
> static void rcu_check_gp_kthread_starvation(struct rcu_state *rsp)
> @@ -1197,10 +1207,11 @@ static void rcu_check_gp_kthread_starvation(struct rcu_state *rsp)
> j = jiffies;
> gpa = READ_ONCE(rsp->gp_activity);
> if (j - gpa > 2 * HZ) {
> - pr_err("%s kthread starved for %ld jiffies! g%lu c%lu f%#x s%d ->state=%#lx\n",
> + pr_err("%s kthread starved for %ld jiffies! g%lu c%lu f%#x %s(%d) ->state=%#lx\n",
> rsp->name, j - gpa,
> rsp->gpnum, rsp->completed,
> - rsp->gp_flags, rsp->gp_state,
> + rsp->gp_flags,
> + gp_state_getname(rsp->gp_state), rsp->gp_state,
> rsp->gp_kthread ? rsp->gp_kthread->state : ~0);
> if (rsp->gp_kthread)
> sched_show_task(rsp->gp_kthread);
> diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
> index f32bebb6bc90..f0304988e3f8 100644
> --- a/kernel/rcu/tree.h
> +++ b/kernel/rcu/tree.h
> @@ -544,6 +544,15 @@ struct rcu_state {
> #define RCU_GP_DOING_FQS 4 /* Wait done for force-quiescent-state time. */
> #define RCU_GP_CLEANUP 5 /* Grace-period cleanup started. */
> #define RCU_GP_CLEANED 6 /* Grace-period cleanup complete. */
> +static char * const gp_state_names[] = {

Same comment about "const char * const", but also, should this really go
in a header file? Do any circumstances exist where this header could
get included in more than one source file in a given build? If so,
multiple copies of this array could potentially end up in the binary, if
the compiler fails to merge them.

> + "RCU_GP_IDLE",
> + "RCU_GP_WAIT_GPS",
> + "RCU_GP_DONE_GPS",
> + "RCU_GP_WAIT_FQS",
> + "RCU_GP_DOING_FQS",
> + "RCU_GP_CLEANUP",
> + "RCU_GP_CLEANED",
> +};
>
> extern struct list_head rcu_struct_flavors;
>
> --
> 2.5.2
>