From: Paul E. McKenney Date: Mon, 19 Jun 2017 17:32:23 +0000 (-0700) Subject: rcu: Add event tracing to ->gp_tasks update at GP start X-Git-Tag: v4.14-rc1~174^2^2^2~8 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=c5ebe66ce774126b888617cab658f6556d23365e;p=platform%2Fkernel%2Flinux-rpi.git rcu: Add event tracing to ->gp_tasks update at GP start There is currently event tracing to track when a task is preempted within a preemptible RCU read-side critical section, and also when that task subsequently reaches its outermost rcu_read_unlock(), but none indicating when a new grace period starts when that grace period must wait on pre-existing readers that have been been preempted at least once since the beginning of their current RCU read-side critical sections. This commit therefore adds an event trace at grace-period start in the case where there are such readers. Note that only the first reader in the list is traced. Signed-off-by: Paul E. McKenney Acked-by: Steven Rostedt (VMware) --- diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 14ba496..3e3f92e 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -636,10 +636,17 @@ static int rcu_print_task_exp_stall(struct rcu_node *rnp) */ static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp) { + struct task_struct *t; + RCU_LOCKDEP_WARN(preemptible(), "rcu_preempt_check_blocked_tasks() invoked with preemption enabled!!!\n"); WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp)); - if (rcu_preempt_has_tasks(rnp)) + if (rcu_preempt_has_tasks(rnp)) { rnp->gp_tasks = rnp->blkd_tasks.next; + t = container_of(rnp->gp_tasks, struct task_struct, + rcu_node_entry); + trace_rcu_unlock_preempted_task(TPS("rcu_preempt-GPS"), + rnp->gpnum, t->pid); + } WARN_ON_ONCE(rnp->qsmask); }