Hello! This series removes the long-standing restriction preventing holding of scheduler locks across rcu_read_unlock() unless interrupts have been disabled across the entire RCU read-side critical section. For example, with this series, the following code is now perfectly legal, and is in fact tested by rcutorture: // Preemption is enabled. rcu_read_lock(); do_something(); raw_spin_lock_irqsave(¤t->pi_lock, flags); rcu_read_unlock(); raw_spin_unlock_irqrestore(¤t->pi_lock, flags); This change was enabled by the earlier changes that turn on scheduler-clock interrupts for nohz_full CPUs that take too long to report a quiescent state during a given grace period. (Yes, nohz_full CPUs executing in userspace still have their quiescent states implicitly reported by the RCU grace-period kthread!) And here is the series: 1. Add KCSAN stubs to update.c. 2. Make rcu_read_unlock_special() safe for rq/pi locks. 3. Don't set nesting depth negative in rcu_preempt_deferred_qs(), courtesy of Lai Jiangshan. 4. Remove unused ->rcu_read_unlock_special.b.deferred_qs field, courtesy of Lai Jiangshan. 5. Don't use negative nesting depth in __rcu_read_unlock(), courtesy of Lai Jiangshan. 6. Add test of holding scheduler locks across rcu_read_unlock(). Thanx, Paul ------------------------------------------------------------------------ include/linux/sched.h | 2 +- kernel/rcu/rcutorture.c | 10 +++++++++- kernel/rcu/tree_exp.h | 31 +++++-------------------------- kernel/rcu/tree_plugin.h | 45 +++++++++++++++------------------------------ kernel/rcu/update.c | 13 +++++++++++++ 5 files changed, 43 insertions(+), 58 deletions(-)
