From: "Paul E. McKenney" <paulmck@kernel.org>
To: rcu@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com,
rostedt@goodmis.org, Kunwu Chan <kunwu.chan@gmail.com>,
Zqiang <qiang.zhang@linux.dev>, Boqun Feng <boqun@kernel.org>,
"Paul E . McKenney" <paulmck@kernel.org>
Subject: [PATCH v2 21/21] srcutree: Preserve IRQ state in synchronize_srcu_atomic() callchain
Date: Wed, 7 Oct 2026 13:59:24 -0700 [thread overview]
Message-ID: <20261007205924.1983367-21-paulmck@kernel.org> (raw)
In-Reply-To: <546c81a7-f677-4d8e-a304-746b227058b0@paulmck-laptop>
From: Kunwu Chan <kunwu.chan@gmail.com>
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@linux.dev>
Signed-off-by: Zqiang <qiang.zhang@linux.dev>
Signed-off-by: Kunwu Chan <kunwu.chan@gmail.com>
Acked-by: Boqun Feng <boqun@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
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 7890f7c7c2ee7..c8209aa6552a1 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. */
@@ -1220,10 +1221,11 @@ 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))
@@ -2023,6 +2025,7 @@ 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)
@@ -2040,10 +2043,10 @@ 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;
@@ -2053,7 +2056,7 @@ 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);
@@ -2069,10 +2072,10 @@ 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) {
@@ -2119,6 +2122,7 @@ 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;
@@ -2149,9 +2153,9 @@ 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;
@@ -2162,7 +2166,7 @@ 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
@@ -2200,9 +2204,9 @@ 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();
--
2.40.1
prev parent reply other threads:[~2026-10-07 20:59 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-07 20:59 [PATCH v2 0/21] Add atomic SRCU &c for v7.4 Paul E. McKenney
2026-10-07 20:59 ` [PATCH v2 01/21] srcutiny: Make a Tiny SRCU grace period imply an RCU grace period Paul E. McKenney
2026-10-07 20:59 ` [PATCH v2 02/21] srcutree: Suppress srcu_advance_state() mutex_lock in atomic Paul E. McKenney
2026-10-07 20:59 ` [PATCH v2 03/21] srcutree: Suppress to-big transition for atomic SRCU Paul E. McKenney
2026-10-07 20:59 ` [PATCH v2 04/21] srcutree: Add an atomic Tree SRCU Paul E. McKenney
2026-10-08 7:39 ` David Woodhouse
2026-10-08 15:51 ` Paul E. McKenney
2026-10-07 20:59 ` [PATCH v2 05/21] srcutiny: Add an atomic Tiny SRCU Paul E. McKenney
2026-10-07 20:59 ` [PATCH v2 06/21] rcutorture: Add support for testing synchronize_srcu_atomic() Paul E. McKenney
2026-10-07 20:59 ` [PATCH v2 07/21] srcutree: Disable preemption across synchronize_srcu_atomic() Paul E. McKenney
2026-10-07 20:59 ` [PATCH v2 08/21] srcu: Use IRQ_WORK_INIT_HARD for srcu's irq_work Paul E. McKenney
2026-10-07 20:59 ` [PATCH v2 09/21] srcutree: Warn if Tiny SRCU readers are preempted Paul E. McKenney
2026-10-07 20:59 ` [PATCH v2 10/21] srcutree: Explicitly note DEFINE_SRCU() needs for srcu_barrier() Paul E. McKenney
2026-10-07 20:59 ` [PATCH v2 11/21] rcutorture: Add atomic-SRCU support to torture.sh Paul E. McKenney
2026-10-07 20:59 ` [PATCH v2 12/21] srcutree: Add reader-free fastpath to synchronize_srcu_atomic() Paul E. McKenney
2026-10-07 20:59 ` [PATCH v2 13/21] srcutree: Skip callback scheduling for atomic SRCU grace periods Paul E. McKenney
2026-10-07 20:59 ` [PATCH v2 14/21] srcutree: Remove srcu_barrier() sleep for atomic SRCU Paul E. McKenney
2026-10-07 20:59 ` [PATCH v2 15/21] srcu: Restrict atomic-SRCU non_block annotation to task context Paul E. McKenney
2026-10-07 20:59 ` [PATCH v2 16/21] srcutree: Make init_srcu_struct_atomic() prevent transition to big Paul E. McKenney
2026-10-07 20:59 ` [PATCH v2 17/21] srcutree: Don't transition atomic SRCU to big in srcu_gp_end() Paul E. McKenney
2026-10-07 20:59 ` [PATCH v2 18/21] srcutree: Skip torture to-big transition for atomic SRCU Paul E. McKenney
2026-10-07 20:59 ` [PATCH v2 19/21] srcutree: Add lockdep and early-boot checks to synchronize_srcu_atomic() Paul E. McKenney
2026-10-07 20:59 ` [PATCH v2 20/21] srcutiny: " Paul E. McKenney
2026-10-07 20:59 ` Paul E. McKenney [this message]
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