On Sun, Mar 24, 2024 at 08:42:24PM +0800, Zqiang wrote:
> This commit also allows rcutorture to support srcu double call test
> with CONFIG_DEBUG_OBJECTS_RCU_HEAD option enabled. since the spinlock
^ Comma ","?
> will be called in call_srcu(), in RT-kernel, the spinlock is sleepable,
You lost me on "the spinlock will be called in call_srcu()".
> therefore remove disable-irq and disable-preempt protection.
>
> Signed-off-by: Zqiang <[email protected]>
Nice! A question below.
> ---
> kernel/rcu/rcutorture.c | 36 +++++++++++++++++++++---------------
> 1 file changed, 21 insertions(+), 15 deletions(-)
>
> diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
> index 3f9c3766f52b..6571a69142f8 100644
> --- a/kernel/rcu/rcutorture.c
> +++ b/kernel/rcu/rcutorture.c
> @@ -388,6 +388,7 @@ struct rcu_torture_ops {
> int extendables;
> int slow_gps;
> int no_pi_lock;
> + int debug_objects;
> const char *name;
> };
>
> @@ -573,6 +574,7 @@ static struct rcu_torture_ops rcu_ops = {
> .irq_capable = 1,
> .can_boost = IS_ENABLED(CONFIG_RCU_BOOST),
> .extendables = RCUTORTURE_MAX_EXTEND,
> + .debug_objects = 1,
> .name = "rcu"
> };
>
> @@ -743,6 +745,7 @@ static struct rcu_torture_ops srcu_ops = {
> .cbflood_max = 50000,
> .irq_capable = 1,
> .no_pi_lock = IS_ENABLED(CONFIG_TINY_SRCU),
> + .debug_objects = 1,
> .name = "srcu"
> };
>
> @@ -782,6 +785,7 @@ static struct rcu_torture_ops srcud_ops = {
> .cbflood_max = 50000,
> .irq_capable = 1,
> .no_pi_lock = IS_ENABLED(CONFIG_TINY_SRCU),
> + .debug_objects = 1,
> .name = "srcud"
> };
>
> @@ -3481,35 +3485,37 @@ static void rcu_test_debug_objects(void)
> #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
> struct rcu_head rh1;
> struct rcu_head rh2;
> + int idx;
> +
> + if (!cur_ops->debug_objects || !cur_ops->call ||
> + !cur_ops->cb_barrier)
If this is built-in, could we please WARN if there is a conflict?
Otherwise, it looks like the test succeeded.
> + return;
> +
> struct rcu_head *rhp = kmalloc(sizeof(*rhp), GFP_KERNEL);
>
> init_rcu_head_on_stack(&rh1);
> init_rcu_head_on_stack(&rh2);
> - pr_alert("%s: WARN: Duplicate call_rcu() test starting.\n",
> KBUILD_MODNAME);
> + pr_alert("%s: WARN: Duplicate call_%s() test starting.\n",
> KBUILD_MODNAME, cur_ops->name);
>
> /* Try to queue the rh2 pair of callbacks for the same grace period. */
> - preempt_disable(); /* Prevent preemption from interrupting test. */
What makes us not need this preempt_disable() in the RCU case?
> - rcu_read_lock(); /* Make it impossible to finish a grace period. */
> - call_rcu_hurry(&rh1, rcu_torture_leak_cb); /* Start grace period. */
> - local_irq_disable(); /* Make it harder to start a new grace period. */
Same question for the local_irq_disable()?
> - call_rcu_hurry(&rh2, rcu_torture_leak_cb);
> - call_rcu_hurry(&rh2, rcu_torture_err_cb); /* Duplicate callback. */
> + idx = cur_ops->readlock(); /* Make it impossible to finish a grace
> period. */
> + cur_ops->call(&rh1, rcu_torture_leak_cb); /* Start grace period. */
> + cur_ops->call(&rh2, rcu_torture_leak_cb);
> + cur_ops->call(&rh2, rcu_torture_err_cb); /* Duplicate callback. */
> if (rhp) {
> - call_rcu_hurry(rhp, rcu_torture_leak_cb);
> - call_rcu_hurry(rhp, rcu_torture_err_cb); /* Another duplicate
> callback. */
> + cur_ops->call(rhp, rcu_torture_leak_cb);
> + cur_ops->call(rhp, rcu_torture_err_cb); /* Another duplicate
> callback. */
> }
> - local_irq_enable();
> - rcu_read_unlock();
> - preempt_enable();
> + cur_ops->readunlock(idx);
>
> /* Wait for them all to get done so we can safely return. */
> - rcu_barrier();
> - pr_alert("%s: WARN: Duplicate call_rcu() test complete.\n",
> KBUILD_MODNAME);
> + cur_ops->cb_barrier();
> + pr_alert("%s: WARN: Duplicate call_%s() test complete.\n",
> KBUILD_MODNAME, cur_ops->name);
> destroy_rcu_head_on_stack(&rh1);
> destroy_rcu_head_on_stack(&rh2);
> kfree(rhp);
> #else /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
> - pr_alert("%s: !CONFIG_DEBUG_OBJECTS_RCU_HEAD, not testing duplicate
> call_rcu()\n", KBUILD_MODNAME);
> + pr_alert("%s: !CONFIG_DEBUG_OBJECTS_RCU_HEAD, not testing duplicate
> call_%s()\n", KBUILD_MODNAME, cur_ops->name);
> #endif /* #else #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
It might be possible to simplify the code by turning this #ifdef into
IS_ENABLED().
Thanx, Paul
> }
>
> --
> 2.17.1
>
