mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-28 11:49:32 +00:00
rcu/tree: Add a warning if CPU being onlined did not report QS already
Currently, rcu_cpu_starting() checks to see if the RCU core expects a quiescent state from the incoming CPU. However, the current interaction between RCU quiescent-state reporting and CPU-hotplug operations should mean that the incoming CPU never needs to report a quiescent state. First, the outgoing CPU reports a quiescent state if needed. Second, the race where the CPU is leaving just as RCU is initializing a new grace period is handled by an explicit check for this condition. Third, the CPU's leaf rcu_node structure's ->lock serializes these checks. This means that if rcu_cpu_starting() ever feels the need to report a quiescent state, then there is a bug somewhere in the CPU hotplug code or the RCU grace-period handling code. This commit therefore adds a WARN_ON_ONCE() to bring that bug to everyone's attention. Cc: Neeraj Upadhyay <neeraju@codeaurora.org> Suggested-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
parent
a3941517fc
commit
9f866dac94
1 changed files with 3 additions and 1 deletions
|
@ -4075,7 +4075,9 @@ void rcu_cpu_starting(unsigned int cpu)
|
|||
rcu_gpnum_ovf(rnp, rdp); /* Offline-induced counter wrap? */
|
||||
rdp->rcu_onl_gp_seq = READ_ONCE(rcu_state.gp_seq);
|
||||
rdp->rcu_onl_gp_flags = READ_ONCE(rcu_state.gp_flags);
|
||||
if (rnp->qsmask & mask) { /* RCU waiting on incoming CPU? */
|
||||
|
||||
/* An incoming CPU should never be blocking a grace period. */
|
||||
if (WARN_ON_ONCE(rnp->qsmask & mask)) { /* RCU waiting on incoming CPU? */
|
||||
rcu_disable_urgency_upon_qs(rdp);
|
||||
/* Report QS -after- changing ->qsmaskinitnext! */
|
||||
rcu_report_qs_rnp(mask, rnp, rnp->gp_seq, flags);
|
||||
|
|
Loading…
Reference in a new issue