Messages in this thread Patch in this message | | | From | paulmck@kernel ... | Subject | [PATCH tip/core/rcu 6/6] rcutorture: Add test of holding scheduler locks across rcu_read_unlock() | Date | Wed, 15 Apr 2020 10:56:14 -0700 |
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From: "Paul E. McKenney" <paulmck@kernel.org>
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 <mingo@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Juri Lelli <juri.lelli@redhat.com> Cc: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> --- 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) -- 2.9.5
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