From: Zqiang <[email protected]> [ Upstream commit 1bba3900ca18bdae28d1b9fa10f16a8f8cb2ada1 ]
In the preparation stage of CPU online, if the corresponding the rdp's->nocb_cb_kthread does not exist, will be created, there is a situation where the rdp's rcuop kthreads creation fails, and then de-offload this CPU's rdp, does not assign this CPU's rdp->nocb_cb_kthread pointer, but this rdp's->nocb_gp_rdp and rdp's->rdp_gp->nocb_gp_kthread is still valid. This will cause the subsequent re-offload operation of this offline CPU, which will pass the conditional check and the kthread_unpark() will access invalid rdp's->nocb_cb_kthread pointer. This commit therefore use rdp's->nocb_gp_kthread instead of rdp_gp's->nocb_gp_kthread for safety check. Signed-off-by: Zqiang <[email protected]> Reviewed-by: Frederic Weisbecker <[email protected]> Signed-off-by: Neeraj Upadhyay (AMD) <[email protected]> [ Minor conflict resolved. ] Signed-off-by: Jianqiang kang <[email protected]> --- kernel/rcu/tree_nocb.h | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h index 7c28d154b094..2f501de7bec9 100644 --- a/kernel/rcu/tree_nocb.h +++ b/kernel/rcu/tree_nocb.h @@ -1112,7 +1112,6 @@ static long rcu_nocb_rdp_offload(void *arg) struct rcu_segcblist *cblist = &rdp->cblist; unsigned long flags; int wake_gp; - struct rcu_data *rdp_gp = rdp->nocb_gp_rdp; WARN_ON_ONCE(rdp->cpu != raw_smp_processor_id()); /* @@ -1122,7 +1121,7 @@ static long rcu_nocb_rdp_offload(void *arg) if (!rdp->nocb_gp_rdp) return -EINVAL; - if (WARN_ON_ONCE(!rdp_gp->nocb_gp_kthread)) + if (WARN_ON_ONCE(!rdp->nocb_gp_kthread)) return -EINVAL; pr_info("Offloading %d\n", rdp->cpu); @@ -1151,7 +1150,7 @@ static long rcu_nocb_rdp_offload(void *arg) */ wake_gp = rdp_offload_toggle(rdp, true, flags); if (wake_gp) - wake_up_process(rdp_gp->nocb_gp_kthread); + wake_up_process(rdp->nocb_gp_kthread); swait_event_exclusive(rdp->nocb_state_wq, rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_CB) && rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_GP)); -- 2.34.1
