Merge tag 'locking-urgent-2026-10-18' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Merge commit. Changes below are compared with the first parent: 32c52ec8.
Changes
4 files changed · +62 −33
| File | Status | Add | Del | Content |
|---|---|---|---|---|
| include/linux/futex.h | modified | +11 | −8 | View file |
| include/linux/futex_types.h | modified | +2 | −0 | View file |
| include/linux/irq-entry-common.h | modified | +21 | −2 | View file |
| kernel/futex/core.c | modified | +28 | −23 | View file |
include/linux/futex.h
View filediff --git a/include/linux/futex.h b/include/linux/futex.h
index 18ed18d..a895d8c 100644
--- a/include/linux/futex.h
+++ b/include/linux/futex.h
@@ -23,28 +23,32 @@ struct task_struct;
* 01 : Shared futex (PTHREAD_PROCESS_SHARED)
* mapped on a file (reference on the underlying inode)
* 10 : Shared futex (PTHREAD_PROCESS_SHARED)
- * (but private mapping on an mm, and reference taken on it)
+ * (but private mapping on an mm)
*/
-#define FUT_OFF_INODE 1 /* We set bit 0 if key has a reference on inode */
-#define FUT_OFF_MMSHARED 2 /* We set bit 1 if key has a reference on mm */
+#define FUT_OFF_INODE 1 /* We set bit 0 if shared key identifies an inode */
+#define FUT_OFF_MMSHARED 2 /* We set bit 1 if shared key identifies an mm */
union futex_key {
+ /* For FUT_OFF_INODE */
struct {
u64 i_seq;
unsigned long pgoff;
unsigned int offset;
/* unsigned int node; */
} shared;
+
+ /* For FUT_OFF_MMSHARED or private */
struct {
union {
- struct mm_struct *mm;
- u64 __tmp;
+ struct mm_struct *mm; /* for private */
+ u64 mm_seq; /* for FUT_OFF_MMSHARED */
};
unsigned long address;
unsigned int offset;
/* unsigned int node; */
} private;
+
struct {
u64 ptr;
unsigned long word;
@@ -152,11 +156,10 @@ static inline void futex_set_vdso_cs_range(struct futex_mm_data *fd, unsigned in
static inline void futex_fixup_robust_unlock(struct pt_regs *regs) { }
#endif /* !CONFIG_FUTEX_ROBUST_UNLOCK */
-
-#if defined(CONFIG_FUTEX_PRIVATE_HASH) || defined(CONFIG_FUTEX_ROBUST_UNLOCK)
+#ifdef CONFIG_FUTEX
void futex_mm_init(struct mm_struct *mm);
#else
static inline void futex_mm_init(struct mm_struct *mm) { }
-#endif
+#endif /* !CONFIG_FUTEX */
#endif /* _LINUX_FUTEX_H */
include/linux/futex_types.h
View filediff --git a/include/linux/futex_types.h b/include/linux/futex_types.h
index d320c05..34b16f2 100644
--- a/include/linux/futex_types.h
+++ b/include/linux/futex_types.h
@@ -85,10 +85,12 @@ struct futex_unlock_cs_ranges { };
* struct futex_mm_data - Futex related per MM data
* @phash: Futex private hash related data
* @unlock: Futex unlock VDSO critical sections
+ * @unique_id: Unique ID of the MM, for FUT_OFF_MMSHARED futexes
*/
struct futex_mm_data {
struct futex_mm_phash phash;
struct futex_unlock_cs_ranges unlock;
+ atomic64_t unique_id;
};
#else /* CONFIG_FUTEX */
struct futex_sched_data { };
include/linux/irq-entry-common.h
View filediff --git a/include/linux/irq-entry-common.h b/include/linux/irq-entry-common.h
index 0bb6c03..c74b5c8 100644
--- a/include/linux/irq-entry-common.h
+++ b/include/linux/irq-entry-common.h
@@ -468,6 +468,25 @@ static inline void irqentry_exit_to_kernel_mode_preempt(struct pt_regs *regs,
irqentry_exit_cond_resched();
}
+/*
+ * The deferred hrtimer rearm is the tail of the timer interrupt, moved to the
+ * interrupt return path so that it runs after a possible reschedule. By now
+ * irq_exit_rcu() has left lockdep's hardirq context. Re-enter it for the
+ * rearm, so that the hrtimer base lock and the timekeeping sequence count are
+ * not chained onto the locks held by the interrupted context, which would add
+ * new lock chains for every lock stack an interrupt hits.
+ *
+ * The rearm on return to user mode needs no such annotation: no locks are
+ * held there, so it uses the same lock chains as the rearm in hardirq
+ * context.
+ */
+static __always_inline void irqentry_hrtimer_rearm_deferred(void)
+{
+ lockdep_hardirq_enter();
+ hrtimer_rearm_deferred();
+ lockdep_hardirq_exit();
+}
+
/**
* irqentry_exit_to_kernel_mode_after_preempt - Establish trace, lockdep and RCU state
* @regs: Pointer to current's pt_regs
@@ -491,7 +510,7 @@ irqentry_exit_to_kernel_mode_after_preempt(struct pt_regs *regs, irqentry_state_
*/
if (state.exit_rcu) {
instrumentation_begin();
- hrtimer_rearm_deferred();
+ irqentry_hrtimer_rearm_deferred();
/* Tell the tracer that IRET will enable interrupts */
trace_hardirqs_on_prepare();
lockdep_hardirqs_on_prepare();
@@ -502,7 +521,7 @@ irqentry_exit_to_kernel_mode_after_preempt(struct pt_regs *regs, irqentry_state_
}
instrumentation_begin();
- hrtimer_rearm_deferred();
+ irqentry_hrtimer_rearm_deferred();
/* Covers both tracing and lockdep */
trace_hardirqs_on();
instrumentation_end();
kernel/futex/core.c
View filediff --git a/kernel/futex/core.c b/kernel/futex/core.c
index 095f9fe..a240638 100644
--- a/kernel/futex/core.c
+++ b/kernel/futex/core.c
@@ -439,45 +439,51 @@ struct hrtimer_sleeper *futex_setup_timer(ktime_t *time, struct hrtimer_sleeper
}
/*
- * Generate a machine wide unique identifier for this inode.
+ * Generate a machine wide unique identifier for this object (inode or mm).
*
* This relies on u64 not wrapping in the life-time of the machine; which with
* 1ns resolution means almost 585 years.
- *
- * This further relies on the fact that a well formed program will not unmap
- * the file while it has a (shared) futex waiting on it. This mapping will have
- * a file reference which pins the mount and inode.
- *
- * If for some reason an inode gets evicted and read back in again, it will get
- * a new sequence number and will _NOT_ match, even though it is the exact same
- * file.
- *
- * It is important that futex_match() will never have a false-positive, esp.
- * for PI futexes that can mess up the state. The above argues that false-negatives
- * are only possible for malformed programs.
*/
-static u64 get_inode_sequence_number(struct inode *inode)
+static u64 get_object_id(atomic64_t *object_seq)
{
- static atomic64_t i_seq;
+ static atomic64_t last_assigned_seq;
u64 old;
- /* Does the inode already have a sequence number? */
- old = atomic64_read(&inode->i_sequence);
+ /* Does the object already have a sequence number? */
+ old = atomic64_read(object_seq);
if (likely(old))
return old;
for (;;) {
- u64 new = atomic64_inc_return(&i_seq);
+ u64 new = atomic64_inc_return(&last_assigned_seq);
if (WARN_ON_ONCE(!new))
continue;
old = 0;
- if (!atomic64_try_cmpxchg_relaxed(&inode->i_sequence, &old, new))
+ if (!atomic64_try_cmpxchg_relaxed(object_seq, &old, new))
return old;
return new;
}
}
+/*
+ * This relies on the fact that a well formed program will not unmap
+ * the file while it has a (shared) futex waiting on it. This mapping will have
+ * a file reference which pins the mount and inode.
+ *
+ * If for some reason an inode gets evicted and read back in again, it will get
+ * a new sequence number and will _NOT_ match, even though it is the exact same
+ * file.
+ *
+ * It is important that futex_match() will never have a false-positive, esp.
+ * for PI futexes that can mess up the state. The above argues that false-negatives
+ * are only possible for malformed programs.
+ */
+static u64 get_inode_sequence_number(struct inode *inode)
+{
+ return get_object_id(&inode->i_sequence);
+}
+
/**
* get_futex_key() - Get parameters which are the keys for a futex
* @uaddr: virtual address of the futex
@@ -683,8 +689,8 @@ again:
goto out;
}
- key->both.offset |= FUT_OFF_MMSHARED; /* ref taken on mm */
- key->private.mm = mm;
+ key->both.offset |= FUT_OFF_MMSHARED;
+ key->private.mm_seq = get_object_id(&mm->futex.unique_id);
key->private.address = address;
} else {
@@ -2055,13 +2061,12 @@ static void futex_robust_unlock_init_mm(struct futex_mm_data *fd)
static inline void futex_robust_unlock_init_mm(struct futex_mm_data *fd) { }
#endif /* !CONFIG_FUTEX_ROBUST_UNLOCK */
-#if defined(CONFIG_FUTEX_PRIVATE_HASH) || defined(CONFIG_FUTEX_ROBUST_UNLOCK)
void futex_mm_init(struct mm_struct *mm)
{
+ atomic64_set(&mm->futex.unique_id, 0);
futex_hash_init_mm(&mm->futex);
futex_robust_unlock_init_mm(&mm->futex);
}
-#endif
int futex_hash_prctl(unsigned long arg2, unsigned long arg3, unsigned long arg4)
{