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Message-Id: <1524450747-22778-16-git-send-email-paulmck@linux.vnet.ibm.com> Date: Sun, 22 Apr 2018 19:32:21 -0700 From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> To: linux-kernel@...r.kernel.org Cc: mingo@...nel.org, jiangshanlai@...il.com, dipankar@...ibm.com, akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com, josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org, rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com, fweisbec@...il.com, oleg@...hat.com, joel.opensrc@...il.com, "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> Subject: [PATCH tip/core/rcu 16/22] EXP: rcu: Add debugging info to assertion The WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp()) in rcu_gp_cleanup() triggers (inexplicably, of course) every so often. This commit therefore extracts more information. Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com> --- kernel/rcu/tree.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 08b72dd02d88..6ad2ac34558f 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -2147,7 +2147,22 @@ static void rcu_gp_cleanup(struct rcu_state *rsp) */ rcu_for_each_node_breadth_first(rsp, rnp) { raw_spin_lock_irq_rcu_node(rnp); - WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp)); +#ifdef CONFIG_PREEMPT_RCU + if (WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp))) { + int i; + struct task_struct *t; + + pr_info("%s: grp: %d-%d level: %d ->gp_tasks %p ->exp_tasks %p &->blkd_tasks: %p offset: %u\n", __func__, rnp->grplo, rnp->grphi, rnp->level, rnp->gp_tasks, rnp->exp_tasks, &rnp->blkd_tasks, (unsigned int)offsetof(typeof(*rnp), blkd_tasks)); + pr_cont("\t->blkd_tasks"); + i = 0; + list_for_each_entry(t, &rnp->blkd_tasks, rcu_node_entry) { + pr_cont(" %p", t); + if (++i >= 10) + break; + } + pr_cont("\n"); + } +#endif /* #ifdef CONFIG_PREEMPT_RCU */ WARN_ON_ONCE(rnp->qsmask); WRITE_ONCE(rnp->completed, rsp->gpnum); rdp = this_cpu_ptr(rsp->rda); -- 2.5.2
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