From d283aa1b04d9ad9ed34bfc2f51ffe0371a16ee3c Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Thu, 20 May 2021 21:08:38 -0700 Subject: [PATCH] rcu: Mark accesses in tree_stall.h This commit marks the accesses in tree_stall.h so as to both avoid undesirable compiler optimizations and to keep KCSAN focused on the accesses of the core algorithm. Signed-off-by: Paul E. McKenney --- kernel/rcu/tree_stall.h | 63 ++++++++++++++++++++++++++----------------------- 1 file changed, 33 insertions(+), 30 deletions(-) diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h index 6dd6c9a..a8d0fcf 100644 --- a/kernel/rcu/tree_stall.h +++ b/kernel/rcu/tree_stall.h @@ -465,9 +465,10 @@ static void rcu_check_gp_kthread_starvation(void) pr_err("%s kthread starved for %ld jiffies! g%ld f%#x %s(%d) ->state=%#x ->cpu=%d\n", rcu_state.name, j, (long)rcu_seq_current(&rcu_state.gp_seq), - data_race(rcu_state.gp_flags), - gp_state_getname(rcu_state.gp_state), rcu_state.gp_state, - gpk ? gpk->__state : ~0, cpu); + data_race(READ_ONCE(rcu_state.gp_flags)), + gp_state_getname(rcu_state.gp_state), + data_race(READ_ONCE(rcu_state.gp_state)), + gpk ? data_race(READ_ONCE(gpk->__state)) : ~0, cpu); if (gpk) { pr_err("\tUnless %s kthread gets sufficient CPU time, OOM is now expected behavior.\n", rcu_state.name); pr_err("RCU grace-period kthread stack dump:\n"); @@ -510,7 +511,7 @@ static void rcu_check_gp_kthread_expired_fqs_timer(void) (long)rcu_seq_current(&rcu_state.gp_seq), data_race(rcu_state.gp_flags), gp_state_getname(RCU_GP_WAIT_FQS), RCU_GP_WAIT_FQS, - gpk->__state); + data_race(READ_ONCE(gpk->__state))); pr_err("\tPossible timer handling issue on cpu=%d timer-softirq=%u\n", cpu, kstat_softirqs_cpu(TIMER_SOFTIRQ, cpu)); } @@ -569,11 +570,11 @@ static void print_other_cpu_stall(unsigned long gp_seq, unsigned long gps) pr_err("INFO: Stall ended before state dump start\n"); } else { j = jiffies; - gpa = data_race(rcu_state.gp_activity); + gpa = data_race(READ_ONCE(rcu_state.gp_activity)); pr_err("All QSes seen, last %s kthread activity %ld (%ld-%ld), jiffies_till_next_fqs=%ld, root ->qsmask %#lx\n", rcu_state.name, j - gpa, j, gpa, - data_race(jiffies_till_next_fqs), - rcu_get_root()->qsmask); + data_race(READ_ONCE(jiffies_till_next_fqs)), + data_race(READ_ONCE(rcu_get_root()->qsmask))); } } /* Rewrite if needed in case of slow consoles. */ @@ -815,32 +816,34 @@ void show_rcu_gp_kthreads(void) struct task_struct *t = READ_ONCE(rcu_state.gp_kthread); j = jiffies; - ja = j - data_race(rcu_state.gp_activity); - jr = j - data_race(rcu_state.gp_req_activity); - js = j - data_race(rcu_state.gp_start); - jw = j - data_race(rcu_state.gp_wake_time); + ja = j - data_race(READ_ONCE(rcu_state.gp_activity)); + jr = j - data_race(READ_ONCE(rcu_state.gp_req_activity)); + js = j - data_race(READ_ONCE(rcu_state.gp_start)); + jw = j - data_race(READ_ONCE(rcu_state.gp_wake_time)); pr_info("%s: wait state: %s(%d) ->state: %#x ->rt_priority %u delta ->gp_start %lu ->gp_activity %lu ->gp_req_activity %lu ->gp_wake_time %lu ->gp_wake_seq %ld ->gp_seq %ld ->gp_seq_needed %ld ->gp_max %lu ->gp_flags %#x\n", rcu_state.name, gp_state_getname(rcu_state.gp_state), - rcu_state.gp_state, t ? t->__state : 0x1ffff, t ? t->rt_priority : 0xffU, - js, ja, jr, jw, (long)data_race(rcu_state.gp_wake_seq), - (long)data_race(rcu_state.gp_seq), - (long)data_race(rcu_get_root()->gp_seq_needed), - data_race(rcu_state.gp_max), - data_race(rcu_state.gp_flags)); + data_race(READ_ONCE(rcu_state.gp_state)), + t ? data_race(READ_ONCE(t->__state)) : 0x1ffff, t ? t->rt_priority : 0xffU, + js, ja, jr, jw, (long)data_race(READ_ONCE(rcu_state.gp_wake_seq)), + (long)data_race(READ_ONCE(rcu_state.gp_seq)), + (long)data_race(READ_ONCE(rcu_get_root()->gp_seq_needed)), + data_race(READ_ONCE(rcu_state.gp_max)), + data_race(READ_ONCE(rcu_state.gp_flags))); rcu_for_each_node_breadth_first(rnp) { if (ULONG_CMP_GE(READ_ONCE(rcu_state.gp_seq), READ_ONCE(rnp->gp_seq_needed)) && - !data_race(rnp->qsmask) && !data_race(rnp->boost_tasks) && - !data_race(rnp->exp_tasks) && !data_race(rnp->gp_tasks)) + !data_race(READ_ONCE(rnp->qsmask)) && !data_race(READ_ONCE(rnp->boost_tasks)) && + !data_race(READ_ONCE(rnp->exp_tasks)) && !data_race(READ_ONCE(rnp->gp_tasks))) continue; pr_info("\trcu_node %d:%d ->gp_seq %ld ->gp_seq_needed %ld ->qsmask %#lx %c%c%c%c ->n_boosts %ld\n", rnp->grplo, rnp->grphi, - (long)data_race(rnp->gp_seq), (long)data_race(rnp->gp_seq_needed), - data_race(rnp->qsmask), - ".b"[!!data_race(rnp->boost_kthread_task)], - ".B"[!!data_race(rnp->boost_tasks)], - ".E"[!!data_race(rnp->exp_tasks)], - ".G"[!!data_race(rnp->gp_tasks)], - data_race(rnp->n_boosts)); + (long)data_race(READ_ONCE(rnp->gp_seq)), + (long)data_race(READ_ONCE(rnp->gp_seq_needed)), + data_race(READ_ONCE(rnp->qsmask)), + ".b"[!!data_race(READ_ONCE(rnp->boost_kthread_task))], + ".B"[!!data_race(READ_ONCE(rnp->boost_tasks))], + ".E"[!!data_race(READ_ONCE(rnp->exp_tasks))], + ".G"[!!data_race(READ_ONCE(rnp->gp_tasks))], + data_race(READ_ONCE(rnp->n_boosts))); if (!rcu_is_leaf_node(rnp)) continue; for_each_leaf_node_possible_cpu(rnp, cpu) { @@ -850,12 +853,12 @@ void show_rcu_gp_kthreads(void) READ_ONCE(rdp->gp_seq_needed))) continue; pr_info("\tcpu %d ->gp_seq_needed %ld\n", - cpu, (long)data_race(rdp->gp_seq_needed)); + cpu, (long)data_race(READ_ONCE(rdp->gp_seq_needed))); } } for_each_possible_cpu(cpu) { rdp = per_cpu_ptr(&rcu_data, cpu); - cbs += data_race(rdp->n_cbs_invoked); + cbs += data_race(READ_ONCE(rdp->n_cbs_invoked)); if (rcu_segcblist_is_offloaded(&rdp->cblist)) show_rcu_nocb_state(rdp); } @@ -937,11 +940,11 @@ void rcu_fwd_progress_check(unsigned long j) if (rcu_gp_in_progress()) { pr_info("%s: GP age %lu jiffies\n", - __func__, jiffies - rcu_state.gp_start); + __func__, jiffies - data_race(READ_ONCE(rcu_state.gp_start))); show_rcu_gp_kthreads(); } else { pr_info("%s: Last GP end %lu jiffies ago\n", - __func__, jiffies - rcu_state.gp_end); + __func__, jiffies - data_race(READ_ONCE(rcu_state.gp_end))); preempt_disable(); rdp = this_cpu_ptr(&rcu_data); rcu_check_gp_start_stall(rdp->mynode, rdp, j); -- 2.7.4