From: Byungchul Park Date: Wed, 9 Nov 2016 08:57:13 +0000 (+0900) Subject: rcu: Only dump stalled-tasks stacks if there was a real stall X-Git-Tag: v4.11-rc1~174^2^2^3~14 X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=c4402b27f1778fad0dbc27b2d88bb06ca22a06f0;p=karo-tx-linux.git rcu: Only dump stalled-tasks stacks if there was a real stall The print_other_cpu_stall() function currently unconditionally invokes rcu_print_detail_task_stall(). This is OK because if there was a stall sufficient to cause print_other_cpu_stall() to be invoked, that stall is very likely to persist through the entire print_other_cpu_stall() execution. However, if the stall did not persist, the variable ndetected will be zero, and that variable is already tested in an "if" statement. Therefore, this commit moves the call to rcu_print_detail_task_stall() under that pre-existing "if" to improve readability, with a very rare reduction in overhead. Signed-off-by: Byungchul Park [ paulmck: Reworked commit log. ] Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett --- diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index cb4e2056ccf3..6232d2f9a84e 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -1379,6 +1379,9 @@ static void print_other_cpu_stall(struct rcu_state *rsp, unsigned long gpnum) (long)rsp->gpnum, (long)rsp->completed, totqlen); if (ndetected) { rcu_dump_cpu_stacks(rsp); + + /* Complain about tasks blocking the grace period. */ + rcu_print_detail_task_stall(rsp); } else { if (READ_ONCE(rsp->gpnum) != gpnum || READ_ONCE(rsp->completed) == gpnum) { @@ -1395,9 +1398,6 @@ static void print_other_cpu_stall(struct rcu_state *rsp, unsigned long gpnum) } } - /* Complain about tasks blocking the grace period. */ - rcu_print_detail_task_stall(rsp); - rcu_check_gp_kthread_starvation(rsp); panic_on_rcu_stall();