From d685514260e21aabd65a9aa8be045766bdaa0549 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 11 Aug 2020 10:33:39 -0700 Subject: rcutorture: Allow pointer leaks to test diagnostic code This commit adds an rcutorture.leakpointer module parameter that intentionally leaks an RCU-protected pointer out of the RCU read-side critical section and checks to see if the corresponding grace period has elapsed, emitting a WARN_ON_ONCE() if so. This module parameter can be used to test facilities like CONFIG_RCU_STRICT_GRACE_PERIOD that end grace periods quickly. While in the area, also document rcutorture.irqreader, which was previously left out. Reported-by Jann Horn Signed-off-by: Paul E. McKenney --- kernel/rcu/rcutorture.c | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'kernel/rcu') diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index 983f82fccb18..916ea4f66e4b 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -87,6 +87,7 @@ torture_param(bool, gp_normal, false, "Use normal (non-expedited) GP wait primitives"); torture_param(bool, gp_sync, false, "Use synchronous GP wait primitives"); torture_param(int, irqreader, 1, "Allow RCU readers from irq handlers"); +torture_param(int, leakpointer, 0, "Leak pointer dereferences from readers"); torture_param(int, n_barrier_cbs, 0, "# of callbacks/kthreads for barrier testing"); torture_param(int, nfakewriters, 4, "Number of RCU fake writer threads"); @@ -1401,6 +1402,9 @@ static bool rcu_torture_one_read(struct torture_random_state *trsp) preempt_enable(); rcutorture_one_extend(&readstate, 0, trsp, rtrsp); WARN_ON_ONCE(readstate & RCUTORTURE_RDR_MASK); + // This next splat is expected behavior if leakpointer, especially + // for CONFIG_RCU_STRICT_GRACE_PERIOD=y kernels. + WARN_ON_ONCE(leakpointer && READ_ONCE(p->rtort_pipe_count) > 1); /* If error or close call, record the sequence of reader protections. */ if ((pipe_count > 1 || completed > 1) && !xchg(&err_segs_recorded, 1)) { -- cgit v1.2.3