The following commit has been merged into the core/rcu branch of tip: Commit-ID: 52b1fc3f798d02a3a9d1cf7a84e98a795223410a Gitweb: https://git.kernel.org/tip/52b1fc3f798d02a3a9d1cf7a84e98a795223410a Author: Paul E. McKenney <[email protected]> AuthorDate: Sat, 28 Mar 2020 18:53:25 -07:00 Committer: Paul E. McKenney <[email protected]> CommitterDate: Mon, 27 Apr 2020 11:03:50 -07:00
rcutorture: Add test of holding scheduler locks across rcu_read_unlock() Now that it should be safe to hold scheduler locks across rcu_read_unlock(), even in cases where the corresponding RCU read-side critical section might have been preempted and boosted, the commit adds a test of this capability to rcutorture. This has been tested on current mainline (which can deadlock in this situation), and lockdep duly reported the expected deadlock. On -rcu, lockdep is silent, thus far, anyway. Cc: Ingo Molnar <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Juri Lelli <[email protected]> Cc: Vincent Guittot <[email protected]> Signed-off-by: Paul E. McKenney <[email protected]> --- kernel/rcu/rcutorture.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index 5453bd5..b348cf8 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -1147,6 +1147,7 @@ static void rcutorture_one_extend(int *readstate, int newstate, struct torture_random_state *trsp, struct rt_read_seg *rtrsp) { + unsigned long flags; int idxnew = -1; int idxold = *readstate; int statesnew = ~*readstate & newstate; @@ -1181,8 +1182,15 @@ static void rcutorture_one_extend(int *readstate, int newstate, rcu_read_unlock_bh(); if (statesold & RCUTORTURE_RDR_SCHED) rcu_read_unlock_sched(); - if (statesold & RCUTORTURE_RDR_RCU) + if (statesold & RCUTORTURE_RDR_RCU) { + bool lockit = !statesnew && !(torture_random(trsp) & 0xffff); + + if (lockit) + raw_spin_lock_irqsave(¤t->pi_lock, flags); cur_ops->readunlock(idxold >> RCUTORTURE_RDR_SHIFT); + if (lockit) + raw_spin_unlock_irqrestore(¤t->pi_lock, flags); + } /* Delay if neither beginning nor end and there was a change. */ if ((statesnew || statesold) && *readstate && newstate)
