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locking: Revert switching guards to _irq_{disable,enable}()

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Revert commit 1b08668748 ("locking: Switch to _irq_{disable,enable}()
variants in cleanup guards").

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 until we've developed stronger tools / debug for such issues.

Fixes: 1b08668748 ("locking: Switch to _irq_{disable,enable}() variants in cleanup guards")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260824105523.GA4121620%40noisy.programming.kicks-ass.net
This commit is contained in:
Peter Zijlstra
2026-08-24 12:49:10 +02:00
parent 0a0d1d55da
commit 46094a7708
2 changed files with 20 additions and 18 deletions
Download Patch File Download Diff File Expand all files Collapse all files

26
include/linux/spinlock.h
View File

@@ -572,12 +572,12 @@ DECLARE_LOCK_GUARD_1_ATTRS(raw_spinlock_nested, __acquires(_T), __releases(*(raw
#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_bh_try, __acquires(_T), __releases(*(raw
#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, __acquires(_T), __releases(*(spinlock_t
#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_try, __acquires(_T), __releases(*(spinloc
#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)

12
kernel/sched/fair.c
View File

@@ -7253,7 +7253,7 @@ static bool distribute_cfs_runtime(struct cfs_bandwidth *cfs_b)
* 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(struct cfs_bandwidth *cfs_b, int overrun)
* 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_rq_runtime(struct cfs_rq *cfs_rq)
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_period_timer(struct hrtimer *timer)
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);