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rcutorture: Update rcutorture_one_extend_check() for lazy preemption

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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>
This commit is contained in:
Paul E. McKenney 2025-02-19 08:51:45 -08:00 committed by Boqun Feng
parent 9fd858cc5a
commit 0be4b19edd
1 changed files with 12 additions and 2 deletions
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14
kernel/rcu/rcutorture.c
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@ -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);
}