Messages in this thread | | | Date | Wed, 15 Apr 2020 10:55:43 -0700 | From | "Paul E. McKenney" <> | Subject | [PATCH tip/core/rcu 0/6] Remove scheduler restriction, update for v5.8 |
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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
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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(-)
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