The rdp->cpu_no_qs.b.norm field is accessed only by the current CPU, but can be accessed both at task level and from interrupt handlers. All accesses from interrupts-enabled code must therefore be marked. This commit therefore converts from __this_cpu_read() to this_cpu_read(), from __this_cpu_write() to this_cpu_write(), and plain C-language accesses to READ_ONCE() and WRITE_ONCE(), but only in interrupts-enabled code.
KCSAN located this issue. Signed-off-by: Paul E. McKenney <[email protected]> --- kernel/rcu/tree.c | 2 +- kernel/rcu/tree_plugin.h | 8 ++++---- 2 files changed, 5 insertions(+), 5 deletions(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index c9780e7c0e2afa..377153e0d93440 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -2540,7 +2540,7 @@ rcu_check_quiescent_state(struct rcu_data *rdp) * Was there a quiescent state since the beginning of the grace * period? If no, then exit and wait for the next call. */ - if (rdp->cpu_no_qs.b.norm) + if (READ_ONCE(rdp->cpu_no_qs.b.norm)) return; /* diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index c3db1ad4a2807a..353effac5a37f1 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -298,11 +298,11 @@ static void rcu_preempt_ctxt_queue(struct rcu_node *rnp, struct rcu_data *rdp) static void rcu_qs(void) { RCU_LOCKDEP_WARN(preemptible(), "rcu_qs() invoked with preemption enabled!!!\n"); - if (__this_cpu_read(rcu_data.cpu_no_qs.b.norm)) { + if (this_cpu_read(rcu_data.cpu_no_qs.b.norm)) { trace_rcu_grace_period(TPS("rcu_preempt"), __this_cpu_read(rcu_data.gp_seq), TPS("cpuqs")); - __this_cpu_write(rcu_data.cpu_no_qs.b.norm, false); + this_cpu_write(rcu_data.cpu_no_qs.b.norm, false); barrier(); /* Coordinate with rcu_flavor_sched_clock_irq(). */ WRITE_ONCE(current->rcu_read_unlock_special.b.need_qs, false); } @@ -952,7 +952,7 @@ void rcu_read_unlock_strict(void) * __rcu_read_unlock(). */ rdp = this_cpu_ptr(&rcu_data); - rdp->cpu_no_qs.b.norm = false; + WRITE_ONCE(rdp->cpu_no_qs.b.norm, false); rcu_report_qs_rdp(rdp); udelay(rcu_unlock_delay); } @@ -980,7 +980,7 @@ static void rcu_qs(void) return; trace_rcu_grace_period(TPS("rcu_sched"), __this_cpu_read(rcu_data.gp_seq), TPS("cpuqs")); - __this_cpu_write(rcu_data.cpu_no_qs.b.norm, false); + this_cpu_write(rcu_data.cpu_no_qs.b.norm, false); if (this_cpu_read(rcu_data.cpu_no_qs.b.exp)) rcu_report_exp_rdp(this_cpu_ptr(&rcu_data)); } -- 2.40.1
