diff options
| author | Linus Torvalds <torvalds@linux-foundation.org> | 2025-09-07 08:26:28 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2025-09-07 08:26:28 -0700 |
| commit | b7369eb7319d0cb94ad2ea5b5486e276339c595a (patch) | |
| tree | e060256497d228532997e1823d3fd9c2e52bb6ad /kernel | |
| parent | 6a8a34a56a07eb5f0b9c41b1f1e6909e372122cd (diff) | |
| parent | d9b05321e21e4b218de4ce8a590bf375f58b6346 (diff) | |
Merge tag 'locking-urgent-2025-09-07' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking fix from Ingo Molnar:
"Fix an 'allocation from atomic context' regression in the futex
vmalloc variant"
* tag 'locking-urgent-2025-09-07' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
futex: Move futex_hash_free() back to __mmput()
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/fork.c | 2 | ||||
| -rw-r--r-- | kernel/futex/core.c | 16 |
2 files changed, 13 insertions, 5 deletions
diff --git a/kernel/fork.c b/kernel/fork.c index af673856499d..c4ada32598bd 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -689,7 +689,6 @@ void __mmdrop(struct mm_struct *mm) mm_pasid_drop(mm); mm_destroy_cid(mm); percpu_counter_destroy_many(mm->rss_stat, NR_MM_COUNTERS); - futex_hash_free(mm); free_mm(mm); } @@ -1138,6 +1137,7 @@ static inline void __mmput(struct mm_struct *mm) if (mm->binfmt) module_put(mm->binfmt->module); lru_gen_del_mm(mm); + futex_hash_free(mm); mmdrop(mm); } diff --git a/kernel/futex/core.c b/kernel/futex/core.c index d9bb5567af0c..125804fbb5cb 100644 --- a/kernel/futex/core.c +++ b/kernel/futex/core.c @@ -1722,12 +1722,9 @@ int futex_mm_init(struct mm_struct *mm) RCU_INIT_POINTER(mm->futex_phash, NULL); mm->futex_phash_new = NULL; /* futex-ref */ + mm->futex_ref = NULL; atomic_long_set(&mm->futex_atomic, 0); mm->futex_batches = get_state_synchronize_rcu(); - mm->futex_ref = alloc_percpu(unsigned int); - if (!mm->futex_ref) - return -ENOMEM; - this_cpu_inc(*mm->futex_ref); /* 0 -> 1 */ return 0; } @@ -1801,6 +1798,17 @@ static int futex_hash_allocate(unsigned int hash_slots, unsigned int flags) } } + if (!mm->futex_ref) { + /* + * This will always be allocated by the first thread and + * therefore requires no locking. + */ + mm->futex_ref = alloc_percpu(unsigned int); + if (!mm->futex_ref) + return -ENOMEM; + this_cpu_inc(*mm->futex_ref); /* 0 -> 1 */ + } + fph = kvzalloc(struct_size(fph, queues, hash_slots), GFP_KERNEL_ACCOUNT | __GFP_NOWARN); if (!fph) |