[PATCH v2] srcu/tiny: Remove preempt_disable/enable() in srcu_gp_start_if_needed()

Zqiang
2025-09-09T13:39:46Z

Currently, the srcu_gp_start_if_needed() is always be invoked in
preempt disable's critical section, this commit therefore remove
redundant preempt_disable/enable() in srcu_gp_start_if_needed()
and adds a call to lockdep_assert_preemption_disabled() in order
to enable lockdep to diagnose mistaken invocations of this function
from preempts-enabled code.

Fixes: 65b4a59557f6 ("srcu: Make Tiny SRCU explicitly disable preemption")
Signed-off-by: Zqiang <qiang.zhang@linux.dev>
---
kernel/rcu/srcutiny.c | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/kernel/rcu/srcutiny.c b/kernel/rcu/srcutiny.c
index b52ec45698e8..b2da188133fc 100644
--- a/kernel/rcu/srcutiny.c
+++ b/kernel/rcu/srcutiny.c
@@ -181,10 +181,9 @@ static void srcu_gp_start_if_needed(struct srcu_struct *ssp)
{
unsigned long cookie;

- preempt_disable(); // Needed for PREEMPT_LAZY
+ lockdep_assert_preemption_disabled();
cookie = get_state_synchronize_srcu(ssp);
if (ULONG_CMP_GE(READ_ONCE(ssp->srcu_idx_max), cookie)) {
- preempt_enable();
return;
}
WRITE_ONCE(ssp->srcu_idx_max, cookie);
@@ -194,7 +193,6 @@ static void srcu_gp_start_if_needed(struct srcu_struct *ssp)
else if (list_empty(&ssp->srcu_work.entry))
list_add(&ssp->srcu_work.entry, &srcu_boot_list);
}
- preempt_enable();
}

/*
--
2.48.1