From: "Paul E. McKenney" paulmck@kernel.org
The rcutorture_one_extend_check() function's last check assumes that if cur_ops->readlock_nesting() returns greater than zero, either the RCUTORTURE_RDR_RCU_1 or the RCUTORTURE_RDR_RCU_2 bit must be set, that is, there must be at least one rcu_read_lock() in effect.
This works for preemptible RCU and for non-preemptible RCU running in a non-preemptible kernel. But it fails for non-preemptible RCU running in a preemptible kernel because then RCU's cur_ops->readlock_nesting() function, which is rcu_torture_readlock_nesting(), will return the PREEMPT_MASK mask bits from preempt_count(). The result will be greater than zero if preemption is disabled, including by the RCUTORTURE_RDR_PREEMPT and RCUTORTURE_RDR_SCHED bits.
This commit therefore adjusts this check to take into account the case fo non-preemptible RCU running in a preemptible kernel.
[boqun: Fix the if condition and add comment]
Reported-by: kernel test robot oliver.sang@intel.com Closes: https://lore.kernel.org/oe-lkp/202502171415.8ec87c87-lkp@intel.com Co-developed-by: Boqun Feng boqun.feng@gmail.com Signed-off-by: Boqun Feng boqun.feng@gmail.com Co-developed-by: Joel Fernandes joelagnelf@nvidia.com Signed-off-by: Joel Fernandes joelagnelf@nvidia.com Signed-off-by: Paul E. McKenney paulmck@kernel.org Tested-by: kernel test robot oliver.sang@intel.com Signed-off-by: Boqun Feng boqun.feng@gmail.com --- kernel/rcu/rcutorture.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-)
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index d26fb1d33ed9..280bff706017 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -1873,6 +1873,8 @@ static void rcu_torture_reader_do_mbchk(long myid, struct rcu_torture *rtp, #define ROEC_ARGS "%s %s: Current %#x To add %#x To remove %#x preempt_count() %#x\n", __func__, s, curstate, new, old, preempt_count() static void rcutorture_one_extend_check(char *s, int curstate, int new, int old, bool insoftirq) { + int mask; + if (!IS_ENABLED(CONFIG_RCU_TORTURE_TEST_CHK_RDR_STATE)) return;
@@ -1902,8 +1904,16 @@ static void rcutorture_one_extend_check(char *s, int curstate, int new, int old, WARN_ONCE(cur_ops->extendables && !(curstate & (RCUTORTURE_RDR_PREEMPT | RCUTORTURE_RDR_SCHED)) && (preempt_count() & PREEMPT_MASK), ROEC_ARGS); - WARN_ONCE(cur_ops->readlock_nesting && - !(curstate & (RCUTORTURE_RDR_RCU_1 | RCUTORTURE_RDR_RCU_2)) && + + /* + * non-preemptible RCU in a preemptible kernel uses "preempt_count() & + * PREEMPT_MASK" as ->readlock_nesting(). + */ + mask = RCUTORTURE_RDR_RCU_1 | RCUTORTURE_RDR_RCU_2; + if (!IS_ENABLED(CONFIG_PREEMPT_RCU)) + mask |= RCUTORTURE_RDR_PREEMPT | RCUTORTURE_RDR_SCHED; + + WARN_ONCE(cur_ops->readlock_nesting && !(curstate & mask) && cur_ops->readlock_nesting() > 0, ROEC_ARGS); }