[PATCH] locking: Revert switching guards to _irq_{disable,enable}()
From: Peter Zijlstra
Date: Mon Aug 24 2026 - 06:58:52 EST
While the guards are properly nested, not all wrapped code is nice, as already
highlighted by that fair.c hunk.
Syzbot found another instance of this pattern in posix_timer_delete(), which
does spin_unlock_irq()+spin_lock_irq() inside scoped_guard(spinlock_irq).
Combined with this patch, that goes sideways most spectacular.
Undo this change, until we've developed stronger tools / debug for such issues.
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
include/linux/spinlock.h | 26 ++++++++++++++------------
kernel/sched/fair.c | 12 ++++++------
2 files changed, 20 insertions(+), 18 deletions(-)
--- a/include/linux/spinlock.h
+++ b/include/linux/spinlock.h
@@ -572,12 +572,12 @@ DECLARE_LOCK_GUARD_1_ATTRS(raw_spinlock_
#define class_raw_spinlock_nested_constructor(_T) WITH_LOCK_GUARD_1_ATTRS(raw_spinlock_nested, _T)
DEFINE_LOCK_GUARD_1(raw_spinlock_irq, raw_spinlock_t,
- raw_spin_lock_irq_disable(_T->lock),
- raw_spin_unlock_irq_enable(_T->lock))
+ raw_spin_lock_irq(_T->lock),
+ raw_spin_unlock_irq(_T->lock))
DECLARE_LOCK_GUARD_1_ATTRS(raw_spinlock_irq, __acquires(_T), __releases(*(raw_spinlock_t **)_T))
#define class_raw_spinlock_irq_constructor(_T) WITH_LOCK_GUARD_1_ATTRS(raw_spinlock_irq, _T)
-DEFINE_LOCK_GUARD_1_COND(raw_spinlock_irq, _try, raw_spin_trylock_irq_disable(_T->lock))
+DEFINE_LOCK_GUARD_1_COND(raw_spinlock_irq, _try, raw_spin_trylock_irq(_T->lock))
DECLARE_LOCK_GUARD_1_ATTRS(raw_spinlock_irq_try, __acquires(_T), __releases(*(raw_spinlock_t **)_T))
#define class_raw_spinlock_irq_try_constructor(_T) WITH_LOCK_GUARD_1_ATTRS(raw_spinlock_irq_try, _T)
@@ -592,13 +592,14 @@ DECLARE_LOCK_GUARD_1_ATTRS(raw_spinlock_
#define class_raw_spinlock_bh_try_constructor(_T) WITH_LOCK_GUARD_1_ATTRS(raw_spinlock_bh_try, _T)
DEFINE_LOCK_GUARD_1(raw_spinlock_irqsave, raw_spinlock_t,
- raw_spin_lock_irq_disable(_T->lock),
- raw_spin_unlock_irq_enable(_T->lock))
+ raw_spin_lock_irqsave(_T->lock, _T->flags),
+ raw_spin_unlock_irqrestore(_T->lock, _T->flags),
+ unsigned long flags)
DECLARE_LOCK_GUARD_1_ATTRS(raw_spinlock_irqsave, __acquires(_T), __releases(*(raw_spinlock_t **)_T))
#define class_raw_spinlock_irqsave_constructor(_T) WITH_LOCK_GUARD_1_ATTRS(raw_spinlock_irqsave, _T)
DEFINE_LOCK_GUARD_1_COND(raw_spinlock_irqsave, _try,
- raw_spin_trylock_irq_disable(_T->lock))
+ raw_spin_trylock_irqsave(_T->lock, _T->flags))
DECLARE_LOCK_GUARD_1_ATTRS(raw_spinlock_irqsave_try, __acquires(_T), __releases(*(raw_spinlock_t **)_T))
#define class_raw_spinlock_irqsave_try_constructor(_T) WITH_LOCK_GUARD_1_ATTRS(raw_spinlock_irqsave_try, _T)
@@ -617,13 +618,13 @@ DECLARE_LOCK_GUARD_1_ATTRS(spinlock_try,
#define class_spinlock_try_constructor(_T) WITH_LOCK_GUARD_1_ATTRS(spinlock_try, _T)
DEFINE_LOCK_GUARD_1(spinlock_irq, spinlock_t,
- spin_lock_irq_disable(_T->lock),
- spin_unlock_irq_enable(_T->lock))
+ spin_lock_irq(_T->lock),
+ spin_unlock_irq(_T->lock))
DECLARE_LOCK_GUARD_1_ATTRS(spinlock_irq, __acquires(_T), __releases(*(spinlock_t **)_T))
#define class_spinlock_irq_constructor(_T) WITH_LOCK_GUARD_1_ATTRS(spinlock_irq, _T)
DEFINE_LOCK_GUARD_1_COND(spinlock_irq, _try,
- spin_trylock_irq_disable(_T->lock))
+ spin_trylock_irq(_T->lock))
DECLARE_LOCK_GUARD_1_ATTRS(spinlock_irq_try, __acquires(_T), __releases(*(spinlock_t **)_T))
#define class_spinlock_irq_try_constructor(_T) WITH_LOCK_GUARD_1_ATTRS(spinlock_irq_try, _T)
@@ -639,13 +640,14 @@ DECLARE_LOCK_GUARD_1_ATTRS(spinlock_bh_t
#define class_spinlock_bh_try_constructor(_T) WITH_LOCK_GUARD_1_ATTRS(spinlock_bh_try, _T)
DEFINE_LOCK_GUARD_1(spinlock_irqsave, spinlock_t,
- spin_lock_irq_disable(_T->lock),
- spin_unlock_irq_enable(_T->lock))
+ spin_lock_irqsave(_T->lock, _T->flags),
+ spin_unlock_irqrestore(_T->lock, _T->flags),
+ unsigned long flags)
DECLARE_LOCK_GUARD_1_ATTRS(spinlock_irqsave, __acquires(_T), __releases(*(spinlock_t **)_T))
#define class_spinlock_irqsave_constructor(_T) WITH_LOCK_GUARD_1_ATTRS(spinlock_irqsave, _T)
DEFINE_LOCK_GUARD_1_COND(spinlock_irqsave, _try,
- spin_trylock_irq_disable(_T->lock))
+ spin_trylock_irqsave(_T->lock, _T->flags))
DECLARE_LOCK_GUARD_1_ATTRS(spinlock_irqsave_try, __acquires(_T), __releases(*(spinlock_t **)_T))
#define class_spinlock_irqsave_try_constructor(_T) WITH_LOCK_GUARD_1_ATTRS(spinlock_irqsave_try, _T)
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7253,7 +7253,7 @@ static bool distribute_cfs_runtime(struc
* period the timer is deactivated until scheduling resumes; cfs_b->idle is
* used to track this state.
*/
-static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun)
+static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun, unsigned long flags)
__must_hold(&cfs_b->lock)
{
int throttled;
@@ -7288,10 +7288,10 @@ static int do_sched_cfs_period_timer(str
* This check is repeated as we release cfs_b->lock while we unthrottle.
*/
while (throttled && cfs_b->runtime > 0) {
- raw_spin_unlock_irq_enable(&cfs_b->lock);
+ raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
/* we can't nest cfs_b->lock while distributing bandwidth */
throttled = distribute_cfs_runtime(cfs_b);
- raw_spin_lock_irq_disable(&cfs_b->lock);
+ raw_spin_lock_irqsave(&cfs_b->lock, flags);
}
/*
@@ -7399,7 +7399,7 @@ static __always_inline void return_cfs_r
static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
{
/* confirm we're still not at a refresh boundary */
- scoped_guard(raw_spinlock_irq, &cfs_b->lock) {
+ scoped_guard(raw_spinlock_irqsave, &cfs_b->lock) {
u64 runtime = 0, slice = sched_cfs_bandwidth_slice();
cfs_b->slack_started = false;
@@ -7484,14 +7484,14 @@ static enum hrtimer_restart sched_cfs_pe
int idle = 0;
int count = 0;
- guard(raw_spinlock_irq)(&cfs_b->lock);
+ CLASS(raw_spinlock_irqsave, cfsb_guard)(&cfs_b->lock);
for (;;) {
overrun = hrtimer_forward_now(timer, cfs_b->period);
if (!overrun)
break;
- idle = do_sched_cfs_period_timer(cfs_b, overrun);
+ idle = do_sched_cfs_period_timer(cfs_b, overrun, cfsb_guard.flags);
if (++count > 3) {
u64 new, old = ktime_to_ns(cfs_b->period);