[PATCH 3/5] srcutree: Preserve IRQ state in synchronize_srcu_atomic() callchain
From: Kunwu Chan
Date: Mon Sep 14 2026 - 06:10:53 EST
synchronize_srcu_atomic() may be called with interrupts disabled, but
its callchain uses raw_spin_lock_irq_rcu_node() /
raw_spin_unlock_irq_rcu_node(), which unconditionally enables
interrupts on unlock. This can incorrectly change the caller's IRQ
state.
Use the irqsave/irqrestore variants for the locks in this callchain
so that the caller's IRQ state is preserved.
Co-developed-by: Zqiang <qiang.zhang@xxxxxxxxx>
Signed-off-by: Zqiang <qiang.zhang@xxxxxxxxx>
Signed-off-by: Kunwu Chan <kunwu.chan@xxxxxxxxx>
---
kernel/rcu/srcutree.c | 42 +++++++++++++++++++++++-------------------
1 file changed, 23 insertions(+), 19 deletions(-)
diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index 6c729e805fb3..d32615d54177 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -985,6 +985,7 @@ static void srcu_gp_end(struct srcu_struct *ssp, bool is_atomic)
bool cbs;
bool last_lvl;
int cpu;
+ unsigned long flags;
unsigned long gpseq;
int idx;
unsigned long mask;
@@ -999,7 +1000,7 @@ static void srcu_gp_end(struct srcu_struct *ssp, bool is_atomic)
mutex_lock(&sup->srcu_cb_mutex);
/* End the current grace period. */
- raw_spin_lock_irq_rcu_node(sup);
+ raw_spin_lock_irqsave_rcu_node(sup, flags);
idx = rcu_seq_state(sup->srcu_gp_seq);
WARN_ON_ONCE(idx != SRCU_STATE_SCAN2);
if (srcu_gp_is_expedited(ssp))
@@ -1010,7 +1011,7 @@ static void srcu_gp_end(struct srcu_struct *ssp, bool is_atomic)
gpseq = rcu_seq_current(&sup->srcu_gp_seq);
if (ULONG_CMP_LT(sup->srcu_gp_seq_needed_exp, gpseq))
WRITE_ONCE(sup->srcu_gp_seq_needed_exp, gpseq);
- raw_spin_unlock_irq_rcu_node(sup);
+ raw_spin_unlock_irqrestore_rcu_node(sup, flags);
if (!is_atomic)
mutex_unlock(&sup->srcu_gp_mutex);
/* A new grace period can start at this point. But only one. */
@@ -1048,12 +1049,12 @@ static void srcu_gp_end(struct srcu_struct *ssp, bool is_atomic)
if (!(gpseq & counter_wrap_check))
for_each_possible_cpu(cpu) {
sdp = per_cpu_ptr(ssp->sda, cpu);
- raw_spin_lock_irq_rcu_node(sdp);
+ raw_spin_lock_irqsave_rcu_node(sdp, flags);
if (ULONG_CMP_GE(gpseq, sdp->srcu_gp_seq_needed + 100))
sdp->srcu_gp_seq_needed = gpseq;
if (ULONG_CMP_GE(gpseq, sdp->srcu_gp_seq_needed_exp + 100))
sdp->srcu_gp_seq_needed_exp = gpseq;
- raw_spin_unlock_irq_rcu_node(sdp);
+ raw_spin_unlock_irqrestore_rcu_node(sdp, flags);
}
/* Callback initiation done, allow grace periods after next. */
@@ -1061,16 +1062,16 @@ static void srcu_gp_end(struct srcu_struct *ssp, bool is_atomic)
mutex_unlock(&sup->srcu_cb_mutex);
/* Start a new grace period if needed. */
- raw_spin_lock_irq_rcu_node(sup);
+ raw_spin_lock_irqsave_rcu_node(sup, flags);
gpseq = rcu_seq_current(&sup->srcu_gp_seq);
if (!rcu_seq_state(gpseq) &&
ULONG_CMP_LT(gpseq, sup->srcu_gp_seq_needed)) {
WARN_ON_ONCE(ssp->srcu_reader_flavor & SRCU_READ_FLAVOR_ATOMIC);
srcu_gp_start(ssp);
- raw_spin_unlock_irq_rcu_node(sup);
+ raw_spin_unlock_irqrestore_rcu_node(sup, flags);
srcu_reschedule(ssp, 0);
} else {
- raw_spin_unlock_irq_rcu_node(sup);
+ raw_spin_unlock_irqrestore_rcu_node(sup, flags);
}
/* Transition to big if needed, but never for atomic SRCU. */
@@ -1221,10 +1222,11 @@ static void srcu_funnel_gp_start(struct srcu_struct *ssp, struct srcu_data *sdp,
static bool try_check_zero(struct srcu_struct *ssp, int idx, int trycount)
{
unsigned long curdelay;
+ unsigned long flags;
- raw_spin_lock_irq_rcu_node(ssp->srcu_sup);
+ raw_spin_lock_irqsave_rcu_node(ssp->srcu_sup, flags);
curdelay = !srcu_get_delay(ssp);
- raw_spin_unlock_irq_rcu_node(ssp->srcu_sup);
+ raw_spin_unlock_irqrestore_rcu_node(ssp->srcu_sup, flags);
for (;;) {
if (srcu_readers_active_idx_check(ssp, idx))
@@ -2024,6 +2026,7 @@ EXPORT_SYMBOL_GPL(srcu_batches_completed);
*/
static void srcu_advance_state(struct srcu_struct *ssp, bool is_atomic)
{
+ unsigned long flags;
int idx;
if (!is_atomic)
@@ -2041,10 +2044,10 @@ static void srcu_advance_state(struct srcu_struct *ssp, bool is_atomic)
*/
idx = rcu_seq_state(smp_load_acquire(&ssp->srcu_sup->srcu_gp_seq)); /* ^^^ */
if (idx == SRCU_STATE_IDLE) {
- raw_spin_lock_irq_rcu_node(ssp->srcu_sup);
+ raw_spin_lock_irqsave_rcu_node(ssp->srcu_sup, flags);
if (ULONG_CMP_GE(ssp->srcu_sup->srcu_gp_seq, ssp->srcu_sup->srcu_gp_seq_needed)) {
WARN_ON_ONCE(rcu_seq_state(ssp->srcu_sup->srcu_gp_seq));
- raw_spin_unlock_irq_rcu_node(ssp->srcu_sup);
+ raw_spin_unlock_irqrestore_rcu_node(ssp->srcu_sup, flags);
if (!is_atomic)
mutex_unlock(&ssp->srcu_sup->srcu_gp_mutex);
return;
@@ -2054,7 +2057,7 @@ static void srcu_advance_state(struct srcu_struct *ssp, bool is_atomic)
WARN_ON_ONCE(ssp->srcu_reader_flavor & SRCU_READ_FLAVOR_ATOMIC);
srcu_gp_start(ssp);
}
- raw_spin_unlock_irq_rcu_node(ssp->srcu_sup);
+ raw_spin_unlock_irqrestore_rcu_node(ssp->srcu_sup, flags);
if (idx != SRCU_STATE_IDLE) {
if (!is_atomic)
mutex_unlock(&ssp->srcu_sup->srcu_gp_mutex);
@@ -2070,10 +2073,10 @@ static void srcu_advance_state(struct srcu_struct *ssp, bool is_atomic)
return; /* readers present, retry later. */
}
srcu_flip(ssp);
- raw_spin_lock_irq_rcu_node(ssp->srcu_sup);
+ raw_spin_lock_irqsave_rcu_node(ssp->srcu_sup, flags);
rcu_seq_set_state(&ssp->srcu_sup->srcu_gp_seq, SRCU_STATE_SCAN2);
ssp->srcu_sup->srcu_n_exp_nodelay = 0;
- raw_spin_unlock_irq_rcu_node(ssp->srcu_sup);
+ raw_spin_unlock_irqrestore_rcu_node(ssp->srcu_sup, flags);
}
if (rcu_seq_state(READ_ONCE(ssp->srcu_sup->srcu_gp_seq)) == SRCU_STATE_SCAN2) {
@@ -2120,6 +2123,7 @@ void synchronize_srcu_atomic(struct srcu_struct *ssp)
{
unsigned long srcu_state;
struct srcu_usage *sup = ssp->srcu_sup;
+ unsigned long flags;
unsigned long rdm0, rdm1;
unsigned long unlocks0, unlocks1;
@@ -2150,9 +2154,9 @@ void synchronize_srcu_atomic(struct srcu_struct *ssp)
}
// One last check for others doing our work for us under the lock.
- raw_spin_lock_irq_rcu_node(sup);
+ raw_spin_lock_irqsave_rcu_node(sup, flags);
if (poll_state_synchronize_srcu(ssp, srcu_state)) {
- raw_spin_unlock_irq_rcu_node(sup);
+ raw_spin_unlock_irqrestore_rcu_node(sup, flags);
atomic_set(&sup->srcu_atomic_gp_flag, 0);
preempt_enable();
return;
@@ -2163,7 +2167,7 @@ void synchronize_srcu_atomic(struct srcu_struct *ssp)
smp_store_release(&sup->srcu_gp_seq_needed, srcu_state); // See srcu_funnel_gp_start().
ASSERT_EXCLUSIVE_WRITER(ssp->srcu_sup->srcu_gp_seq);
srcu_gp_start(ssp);
- raw_spin_unlock_irq_rcu_node(sup);
+ raw_spin_unlock_irqrestore_rcu_node(sup, flags);
//
// Fastpath: If there are no readers at all, neither grace-period
@@ -2201,9 +2205,9 @@ void synchronize_srcu_atomic(struct srcu_struct *ssp)
// poll_state_synchronize_srcu() working, all under ->lock
// and ->srcu_atomic_gp_flag, which excludes concurrent
// sequence-number updates.
- raw_spin_lock_irq_rcu_node(sup);
+ raw_spin_lock_irqsave_rcu_node(sup, flags);
rcu_seq_end(&sup->srcu_gp_seq);
- raw_spin_unlock_irq_rcu_node(sup);
+ raw_spin_unlock_irqrestore_rcu_node(sup, flags);
WARN_ON_ONCE(!poll_state_synchronize_srcu(ssp, srcu_state));
atomic_set_release(&sup->srcu_atomic_gp_flag, 0);
preempt_enable();
--
2.43.0