From: Zqiang <qiang1.zhang@intel.com> mainline inclusion from mainline-v5.19-rc1 commit f596e2ce1c0f250bb3ecc179f611be37e862635f category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/8988 CVE: CVE-2025-39744 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- When booting kernels built with both CONFIG_RCU_STRICT_GRACE_PERIOD=y and CONFIG_PREEMPT_RT=y, the rcu_read_unlock_special() function's invocation of irq_work_queue_on() the init_irq_work() causes the rcu_preempt_deferred_qs_handler() function to work execute in SCHED_FIFO irq_work kthreads. Because rcu_read_unlock_special() is invoked on each rcu_read_unlock() in such kernels, the amount of work just keeps piling up, resulting in a boot-time hang. This commit therefore avoids this hang by using IRQ_WORK_INIT_HARD() instead of init_irq_work(), but only in kernels built with both CONFIG_PREEMPT_RT=y and CONFIG_RCU_STRICT_GRACE_PERIOD=y. Signed-off-by: Zqiang <qiang1.zhang@intel.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Conflicts: kernel/rcu/tree_plugin.h [Context conflicts] Signed-off-by: Jiacheng Yu <yujiacheng3@huawei.com> --- kernel/rcu/tree_plugin.h | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 8f6afaec70db..300b5cca68c1 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -635,8 +635,13 @@ static void rcu_read_unlock_special(struct task_struct *t) !rdp->defer_qs_iw_pending && exp && cpu_online(rdp->cpu)) { // Get scheduler to re-evaluate and call hooks. // If !IRQ_WORK, FQS scan will eventually IPI. - init_irq_work(&rdp->defer_qs_iw, - rcu_preempt_deferred_qs_handler); + if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD) && + IS_ENABLED(CONFIG_PREEMPT_RT)) + rdp->defer_qs_iw = IRQ_WORK_INIT_HARD( + rcu_preempt_deferred_qs_handler); + else + init_irq_work(&rdp->defer_qs_iw, + rcu_preempt_deferred_qs_handler); rdp->defer_qs_iw_pending = true; irq_work_queue_on(&rdp->defer_qs_iw, rdp->cpu); } -- 2.43.0