At present, snp->srcu_have_cbs[idx] is updated by either srcu_funnel_gp_start() or srcu_gp_end(). But as the code changes, now, srcu_funnel_gp_start() is called with srcu read lock held. And its input parameter s, s = rcu_seq_snap(&ssp->srcu_gp_seq), whose counter field always proceeds that of the srcu_gp_seq by one or two. If the seq snap only proceeds by one, the state machine should be in state SRCU_STATE_IDLE, the held srcu read lock will prevent the state machine from moving ahead. So when srcu_gp_end() updates snp->srcu_have_cbs[idx], the idx must be the past idx for srcu_funnel_gp_start() that is cared by nobody. So removing the unnecessary updating in srcu_gp_end(). Test info: Running "tools/testing/selftests/rcutorture/bin/kvm.sh --allcpus --duration 10h --configs 18*SRCU-P" without any failure. Signed-off-by: Pingfan Liu <kernelfans@xxxxxxxxx> Cc: Lai Jiangshan <jiangshanlai@xxxxxxxxx> Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxx> Cc: Frederic Weisbecker <frederic@xxxxxxxxxx> Cc: Josh Triplett <josh@xxxxxxxxxxxxxxxx> Cc: Steven Rostedt <rostedt@xxxxxxxxxxx> Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx> To: rcu@xxxxxxxxxxxxxxx --- kernel/rcu/srcutree.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index 7df59fc8073e..c54d6c04751f 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -783,8 +783,6 @@ static void srcu_gp_end(struct srcu_struct *ssp) last_lvl = snp >= ssp->level[rcu_num_lvls - 1]; if (last_lvl) cbs = ss_state < SRCU_SIZE_BIG || snp->srcu_have_cbs[idx] == gpseq; - snp->srcu_have_cbs[idx] = gpseq; - rcu_seq_set_state(&snp->srcu_have_cbs[idx], 1); sgsne = snp->srcu_gp_seq_needed_exp; if (srcu_invl_snp_seq(sgsne) || ULONG_CMP_LT(sgsne, gpseq)) WRITE_ONCE(snp->srcu_gp_seq_needed_exp, gpseq); -- 2.31.1
