| Author | Tokens | Token Proportion | Commits | Commit Proportion |
|---|---|---|---|---|
| Peter Zijlstra | 1860 | 32.83% | 26 | 16.99% |
| Sebastian Andrzej Siewior | 1813 | 32.00% | 10 | 6.54% |
| Ingo Molnar | 415 | 7.32% | 12 | 7.84% |
| Davidlohr Bueso A | 240 | 4.24% | 2 | 1.31% |
| Thomas Gleixner | 190 | 3.35% | 18 | 11.76% |
| Rusty Russell | 173 | 3.05% | 5 | 3.27% |
| Arnd Bergmann | 134 | 2.36% | 2 | 1.31% |
| Jamie Lokier | 117 | 2.06% | 3 | 1.96% |
| Mel Gorman | 75 | 1.32% | 2 | 1.31% |
| Waiman Long | 67 | 1.18% | 1 | 0.65% |
| Darren Hart | 65 | 1.15% | 4 | 2.61% |
| Shawn Bohrer | 59 | 1.04% | 1 | 0.65% |
| Martin Schwidefsky | 58 | 1.02% | 1 | 0.65% |
| Eric Dumazet | 56 | 0.99% | 1 | 0.65% |
| Matthew Wilcox | 35 | 0.62% | 3 | 1.96% |
| Rasmus Villemoes | 28 | 0.49% | 1 | 0.65% |
| Linus Torvalds (pre-git) | 25 | 0.44% | 5 | 3.27% |
| Andi Kleen | 19 | 0.34% | 2 | 1.31% |
| Yang Tao | 18 | 0.32% | 1 | 0.65% |
| David S. Miller | 18 | 0.32% | 1 | 0.65% |
| Ben Wolsieffer | 17 | 0.30% | 1 | 0.65% |
| Hugh Dickins | 14 | 0.25% | 2 | 1.31% |
| Jakub Jelínek | 14 | 0.25% | 2 | 1.31% |
| Baruch Siach | 12 | 0.21% | 1 | 0.65% |
| Alexey Izbyshev | 12 | 0.21% | 1 | 0.65% |
| Joey Gouly | 12 | 0.21% | 1 | 0.65% |
| Uros Bizjak | 9 | 0.16% | 2 | 1.31% |
| Linus Torvalds | 8 | 0.14% | 2 | 1.31% |
| Dominik Brodowski | 7 | 0.12% | 1 | 0.65% |
| Will Deacon | 7 | 0.12% | 1 | 0.65% |
| Eric Sesterhenn / Snakebyte | 7 | 0.12% | 1 | 0.65% |
| Andrea Arcangeli | 7 | 0.12% | 1 | 0.65% |
| Kirill A. Shutemov | 7 | 0.12% | 1 | 0.65% |
| Vincent Guittot | 6 | 0.11% | 1 | 0.65% |
| Namhyung Kim | 5 | 0.09% | 2 | 1.31% |
| Michel Lespinasse | 5 | 0.09% | 2 | 1.31% |
| Akinobu Mita | 4 | 0.07% | 2 | 1.31% |
| Benjamin Herrenschmidt | 4 | 0.07% | 2 | 1.31% |
| Andrey Vagin | 4 | 0.07% | 1 | 0.65% |
| Nicholas Piggin | 3 | 0.05% | 1 | 0.65% |
| Stephen Rothwell | 3 | 0.05% | 1 | 0.65% |
| Al Viro | 3 | 0.05% | 2 | 1.31% |
| Dominik Dingel | 2 | 0.04% | 1 | 0.65% |
| André Almeida | 2 | 0.04% | 1 | 0.65% |
| Heiko Carstens | 2 | 0.04% | 1 | 0.65% |
| Christoph Hellwig | 2 | 0.04% | 1 | 0.65% |
| Viresh Kumar | 2 | 0.04% | 1 | 0.65% |
| Jack Miller | 2 | 0.04% | 1 | 0.65% |
| Randy Dunlap | 2 | 0.04% | 2 | 1.31% |
| Ravikiran G. Thirumalai | 2 | 0.04% | 1 | 0.65% |
| Mathieu Desnoyers | 2 | 0.04% | 1 | 0.65% |
| Zhang Yi | 2 | 0.04% | 1 | 0.65% |
| Yoann Congal | 2 | 0.04% | 1 | 0.65% |
| Ira Weiny | 1 | 0.02% | 1 | 0.65% |
| Eric W. Biedermann | 1 | 0.02% | 1 | 0.65% |
| Nam Cao | 1 | 0.02% | 1 | 0.65% |
| Jens Axboe | 1 | 0.02% | 1 | 0.65% |
| Alexey Kuznetsov | 1 | 0.02% | 1 | 0.65% |
| Mike Rapoport | 1 | 0.02% | 1 | 0.65% |
| Pierre Peiffer | 1 | 0.02% | 1 | 0.65% |
| Jianyu Zhan | 1 | 0.02% | 1 | 0.65% |
| Yang Yang | 1 | 0.02% | 1 | 0.65% |
| Total | 5666 | 153 |
// SPDX-License-Identifier: GPL-2.0-or-later /* * Fast Userspace Mutexes (which I call "Futexes!"). * (C) Rusty Russell, IBM 2002 * * Generalized futexes, futex requeueing, misc fixes by Ingo Molnar * (C) Copyright 2003 Red Hat Inc, All Rights Reserved * * Removed page pinning, fix privately mapped COW pages and other cleanups * (C) Copyright 2003, 2004 Jamie Lokier * * Robust futex support started by Ingo Molnar * (C) Copyright 2006 Red Hat Inc, All Rights Reserved * Thanks to Thomas Gleixner for suggestions, analysis and fixes. * * PI-futex support started by Ingo Molnar and Thomas Gleixner * Copyright (C) 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com> * Copyright (C) 2006 Timesys Corp., Thomas Gleixner <tglx@timesys.com> * * PRIVATE futexes by Eric Dumazet * Copyright (C) 2007 Eric Dumazet <dada1@cosmosbay.com> * * Requeue-PI support by Darren Hart <dvhltc@us.ibm.com> * Copyright (C) IBM Corporation, 2009 * Thanks to Thomas Gleixner for conceptual design and careful reviews. * * Thanks to Ben LaHaise for yelling "hashed waitqueues" loudly * enough at me, Linus for the original (flawed) idea, Matthew * Kirkwood for proof-of-concept implementation. * * "The futexes are also cursed." * "But they come in a choice of three flavours!" */ #include <linux/compat.h> #include <linux/jhash.h> #include <linux/pagemap.h> #include <linux/debugfs.h> #include <linux/plist.h> #include <linux/gfp.h> #include <linux/vmalloc.h> #include <linux/memblock.h> #include <linux/fault-inject.h> #include <linux/slab.h> #include <linux/prctl.h> #include <linux/rcuref.h> #include <linux/mempolicy.h> #include <linux/mmap_lock.h> #include "futex.h" #include "../locking/rtmutex_common.h" /* * The base of the bucket array and its size are always used together * (after initialization only in futex_hash()), so ensure that they * reside in the same cacheline. */ static struct { unsigned long hashmask; unsigned int hashshift; struct futex_hash_bucket *queues[MAX_NUMNODES]; } __futex_data __read_mostly __aligned(2*sizeof(long)); #define futex_hashmask (__futex_data.hashmask) #define futex_hashshift (__futex_data.hashshift) #define futex_queues (__futex_data.queues) struct futex_private_hash { rcuref_t users; unsigned int hash_mask; struct rcu_head rcu; void *mm; bool custom; bool immutable; struct futex_hash_bucket queues[]; }; /* * Fault injections for futexes. */ #ifdef CONFIG_FAIL_FUTEX static struct { struct fault_attr attr; bool ignore_private; } fail_futex = { .attr = FAULT_ATTR_INITIALIZER, .ignore_private = false, }; static int __init setup_fail_futex(char *str) { return setup_fault_attr(&fail_futex.attr, str); } __setup("fail_futex=", setup_fail_futex); bool should_fail_futex(bool fshared) { if (fail_futex.ignore_private && !fshared) return false; return should_fail(&fail_futex.attr, 1); } #ifdef CONFIG_FAULT_INJECTION_DEBUG_FS static int __init fail_futex_debugfs(void) { umode_t mode = S_IFREG | S_IRUSR | S_IWUSR; struct dentry *dir; dir = fault_create_debugfs_attr("fail_futex", NULL, &fail_futex.attr); if (IS_ERR(dir)) return PTR_ERR(dir); debugfs_create_bool("ignore-private", mode, dir, &fail_futex.ignore_private); return 0; } late_initcall(fail_futex_debugfs); #endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */ #endif /* CONFIG_FAIL_FUTEX */ static struct futex_hash_bucket * __futex_hash(union futex_key *key, struct futex_private_hash *fph); #ifdef CONFIG_FUTEX_PRIVATE_HASH static inline bool futex_key_is_private(union futex_key *key) { /* * Relies on get_futex_key() to set either bit for shared * futexes -- see comment with union futex_key. */ return !(key->both.offset & (FUT_OFF_INODE | FUT_OFF_MMSHARED)); } bool futex_private_hash_get(struct futex_private_hash *fph) { if (fph->immutable) return true; return rcuref_get(&fph->users); } void futex_private_hash_put(struct futex_private_hash *fph) { /* Ignore return value, last put is verified via rcuref_is_dead() */ if (fph->immutable) return; if (rcuref_put(&fph->users)) wake_up_var(fph->mm); } /** * futex_hash_get - Get an additional reference for the local hash. * @hb: ptr to the private local hash. * * Obtain an additional reference for the already obtained hash bucket. The * caller must already own an reference. */ void futex_hash_get(struct futex_hash_bucket *hb) { struct futex_private_hash *fph = hb->priv; if (!fph) return; WARN_ON_ONCE(!futex_private_hash_get(fph)); } void futex_hash_put(struct futex_hash_bucket *hb) { struct futex_private_hash *fph = hb->priv; if (!fph) return; futex_private_hash_put(fph); } static struct futex_hash_bucket * __futex_hash_private(union futex_key *key, struct futex_private_hash *fph) { u32 hash; if (!futex_key_is_private(key)) return NULL; if (!fph) fph = rcu_dereference(key->private.mm->futex_phash); if (!fph || !fph->hash_mask) return NULL; hash = jhash2((void *)&key->private.address, sizeof(key->private.address) / 4, key->both.offset); return &fph->queues[hash & fph->hash_mask]; } static void futex_rehash_private(struct futex_private_hash *old, struct futex_private_hash *new) { struct futex_hash_bucket *hb_old, *hb_new; unsigned int slots = old->hash_mask + 1; unsigned int i; for (i = 0; i < slots; i++) { struct futex_q *this, *tmp; hb_old = &old->queues[i]; spin_lock(&hb_old->lock); plist_for_each_entry_safe(this, tmp, &hb_old->chain, list) { plist_del(&this->list, &hb_old->chain); futex_hb_waiters_dec(hb_old); WARN_ON_ONCE(this->lock_ptr != &hb_old->lock); hb_new = __futex_hash(&this->key, new); futex_hb_waiters_inc(hb_new); /* * The new pointer isn't published yet but an already * moved user can be unqueued due to timeout or signal. */ spin_lock_nested(&hb_new->lock, SINGLE_DEPTH_NESTING); plist_add(&this->list, &hb_new->chain); this->lock_ptr = &hb_new->lock; spin_unlock(&hb_new->lock); } spin_unlock(&hb_old->lock); } } static bool __futex_pivot_hash(struct mm_struct *mm, struct futex_private_hash *new) { struct futex_private_hash *fph; WARN_ON_ONCE(mm->futex_phash_new); fph = rcu_dereference_protected(mm->futex_phash, lockdep_is_held(&mm->futex_hash_lock)); if (fph) { if (!rcuref_is_dead(&fph->users)) { mm->futex_phash_new = new; return false; } futex_rehash_private(fph, new); } rcu_assign_pointer(mm->futex_phash, new); kvfree_rcu(fph, rcu); return true; } static void futex_pivot_hash(struct mm_struct *mm) { scoped_guard(mutex, &mm->futex_hash_lock) { struct futex_private_hash *fph; fph = mm->futex_phash_new; if (fph) { mm->futex_phash_new = NULL; __futex_pivot_hash(mm, fph); } } } struct futex_private_hash *futex_private_hash(void) { struct mm_struct *mm = current->mm; /* * Ideally we don't loop. If there is a replacement in progress * then a new private hash is already prepared and a reference can't be * obtained once the last user dropped it's. * In that case we block on mm_struct::futex_hash_lock and either have * to perform the replacement or wait while someone else is doing the * job. Eitherway, on the second iteration we acquire a reference on the * new private hash or loop again because a new replacement has been * requested. */ again: scoped_guard(rcu) { struct futex_private_hash *fph; fph = rcu_dereference(mm->futex_phash); if (!fph) return NULL; if (fph->immutable) return fph; if (rcuref_get(&fph->users)) return fph; } futex_pivot_hash(mm); goto again; } struct futex_hash_bucket *futex_hash(union futex_key *key) { struct futex_private_hash *fph; struct futex_hash_bucket *hb; again: scoped_guard(rcu) { hb = __futex_hash(key, NULL); fph = hb->priv; if (!fph || futex_private_hash_get(fph)) return hb; } futex_pivot_hash(key->private.mm); goto again; } #else /* !CONFIG_FUTEX_PRIVATE_HASH */ static struct futex_hash_bucket * __futex_hash_private(union futex_key *key, struct futex_private_hash *fph) { return NULL; } struct futex_hash_bucket *futex_hash(union futex_key *key) { return __futex_hash(key, NULL); } #endif /* CONFIG_FUTEX_PRIVATE_HASH */ #ifdef CONFIG_FUTEX_MPOL static int __futex_key_to_node(struct mm_struct *mm, unsigned long addr) { struct vm_area_struct *vma = vma_lookup(mm, addr); struct mempolicy *mpol; int node = FUTEX_NO_NODE; if (!vma) return FUTEX_NO_NODE; mpol = vma_policy(vma); if (!mpol) return FUTEX_NO_NODE; switch (mpol->mode) { case MPOL_PREFERRED: node = first_node(mpol->nodes); break; case MPOL_PREFERRED_MANY: case MPOL_BIND: if (mpol->home_node != NUMA_NO_NODE) node = mpol->home_node; break; default: break; } return node; } static int futex_key_to_node_opt(struct mm_struct *mm, unsigned long addr) { int seq, node; guard(rcu)(); if (!mmap_lock_speculate_try_begin(mm, &seq)) return -EBUSY; node = __futex_key_to_node(mm, addr); if (mmap_lock_speculate_retry(mm, seq)) return -EAGAIN; return node; } static int futex_mpol(struct mm_struct *mm, unsigned long addr) { int node; node = futex_key_to_node_opt(mm, addr); if (node >= FUTEX_NO_NODE) return node; guard(mmap_read_lock)(mm); return __futex_key_to_node(mm, addr); } #else /* !CONFIG_FUTEX_MPOL */ static int futex_mpol(struct mm_struct *mm, unsigned long addr) { return FUTEX_NO_NODE; } #endif /* CONFIG_FUTEX_MPOL */ /** * __futex_hash - Return the hash bucket * @key: Pointer to the futex key for which the hash is calculated * @fph: Pointer to private hash if known * * We hash on the keys returned from get_futex_key (see below) and return the * corresponding hash bucket. * If the FUTEX is PROCESS_PRIVATE then a per-process hash bucket (from the * private hash) is returned if existing. Otherwise a hash bucket from the * global hash is returned. */ static struct futex_hash_bucket * __futex_hash(union futex_key *key, struct futex_private_hash *fph) { int node = key->both.node; u32 hash; if (node == FUTEX_NO_NODE) { struct futex_hash_bucket *hb; hb = __futex_hash_private(key, fph); if (hb) return hb; } hash = jhash2((u32 *)key, offsetof(typeof(*key), both.offset) / sizeof(u32), key->both.offset); if (node == FUTEX_NO_NODE) { /* * In case of !FLAGS_NUMA, use some unused hash bits to pick a * node -- this ensures regular futexes are interleaved across * the nodes and avoids having to allocate multiple * hash-tables. * * NOTE: this isn't perfectly uniform, but it is fast and * handles sparse node masks. */ node = (hash >> futex_hashshift) % nr_node_ids; if (!node_possible(node)) { node = find_next_bit_wrap(node_possible_map.bits, nr_node_ids, node); } } return &futex_queues[node][hash & futex_hashmask]; } /** * futex_setup_timer - set up the sleeping hrtimer. * @time: ptr to the given timeout value * @timeout: the hrtimer_sleeper structure to be set up * @flags: futex flags * @range_ns: optional range in ns * * Return: Initialized hrtimer_sleeper structure or NULL if no timeout * value given */ struct hrtimer_sleeper * futex_setup_timer(ktime_t *time, struct hrtimer_sleeper *timeout, int flags, u64 range_ns) { if (!time) return NULL; hrtimer_setup_sleeper_on_stack(timeout, (flags & FLAGS_CLOCKRT) ? CLOCK_REALTIME : CLOCK_MONOTONIC, HRTIMER_MODE_ABS); /* * If range_ns is 0, calling hrtimer_set_expires_range_ns() is * effectively the same as calling hrtimer_set_expires(). */ hrtimer_set_expires_range_ns(&timeout->timer, *time, range_ns); return timeout; } /* * Generate a machine wide unique identifier for this inode. * * 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 atomic64_t i_seq; u64 old; /* Does the inode already have a sequence number? */ old = atomic64_read(&inode->i_sequence); if (likely(old)) return old; for (;;) { u64 new = atomic64_inc_return(&i_seq); if (WARN_ON_ONCE(!new)) continue; old = 0; if (!atomic64_try_cmpxchg_relaxed(&inode->i_sequence, &old, new)) return old; return new; } } /** * get_futex_key() - Get parameters which are the keys for a futex * @uaddr: virtual address of the futex * @flags: FLAGS_* * @key: address where result is stored. * @rw: mapping needs to be read/write (values: FUTEX_READ, * FUTEX_WRITE) * * Return: a negative error code or 0 * * The key words are stored in @key on success. * * For shared mappings (when @fshared), the key is: * * ( inode->i_sequence, page offset within mapping, offset_within_page ) * * [ also see get_inode_sequence_number() ] * * For private mappings (or when !@fshared), the key is: * * ( current->mm, address, 0 ) * * This allows (cross process, where applicable) identification of the futex * without keeping the page pinned for the duration of the FUTEX_WAIT. * * lock_page() might sleep, the caller should not hold a spinlock. */ int get_futex_key(u32 __user *uaddr, unsigned int flags, union futex_key *key, enum futex_access rw) { unsigned long address = (unsigned long)uaddr; struct mm_struct *mm = current->mm; struct page *page; struct folio *folio; struct address_space *mapping; int node, err, size, ro = 0; bool node_updated = false; bool fshared; fshared = flags & FLAGS_SHARED; size = futex_size(flags); if (flags & FLAGS_NUMA) size *= 2; /* * The futex address must be "naturally" aligned. */ key->both.offset = address % PAGE_SIZE; if (unlikely((address % size) != 0)) return -EINVAL; address -= key->both.offset; if (unlikely(!access_ok(uaddr, size))) return -EFAULT; if (unlikely(should_fail_futex(fshared))) return -EFAULT; node = FUTEX_NO_NODE; if (flags & FLAGS_NUMA) { u32 __user *naddr = (void *)uaddr + size / 2; if (futex_get_value(&node, naddr)) return -EFAULT; if ((node != FUTEX_NO_NODE) && ((unsigned int)node >= MAX_NUMNODES || !node_possible(node))) return -EINVAL; } if (node == FUTEX_NO_NODE && (flags & FLAGS_MPOL)) { node = futex_mpol(mm, address); node_updated = true; } if (flags & FLAGS_NUMA) { u32 __user *naddr = (void *)uaddr + size / 2; if (node == FUTEX_NO_NODE) { node = numa_node_id(); node_updated = true; } if (node_updated && futex_put_value(node, naddr)) return -EFAULT; } key->both.node = node; /* * PROCESS_PRIVATE futexes are fast. * As the mm cannot disappear under us and the 'key' only needs * virtual address, we dont even have to find the underlying vma. * Note : We do have to check 'uaddr' is a valid user address, * but access_ok() should be faster than find_vma() */ if (!fshared) { /* * On no-MMU, shared futexes are treated as private, therefore * we must not include the current process in the key. Since * there is only one address space, the address is a unique key * on its own. */ if (IS_ENABLED(CONFIG_MMU)) key->private.mm = mm; else key->private.mm = NULL; key->private.address = address; return 0; } again: /* Ignore any VERIFY_READ mapping (futex common case) */ if (unlikely(should_fail_futex(true))) return -EFAULT; err = get_user_pages_fast(address, 1, FOLL_WRITE, &page); /* * If write access is not required (eg. FUTEX_WAIT), try * and get read-only access. */ if (err == -EFAULT && rw == FUTEX_READ) { err = get_user_pages_fast(address, 1, 0, &page); ro = 1; } if (err < 0) return err; else err = 0; /* * The treatment of mapping from this point on is critical. The folio * lock protects many things but in this context the folio lock * stabilizes mapping, prevents inode freeing in the shared * file-backed region case and guards against movement to swap cache. * * Strictly speaking the folio lock is not needed in all cases being * considered here and folio lock forces unnecessarily serialization. * From this point on, mapping will be re-verified if necessary and * folio lock will be acquired only if it is unavoidable * * Mapping checks require the folio so it is looked up now. For * anonymous pages, it does not matter if the folio is split * in the future as the key is based on the address. For * filesystem-backed pages, the precise page is required as the * index of the page determines the key. */ folio = page_folio(page); mapping = READ_ONCE(folio->mapping); /* * If folio->mapping is NULL, then it cannot be an anonymous * page; but it might be the ZERO_PAGE or in the gate area or * in a special mapping (all cases which we are happy to fail); * or it may have been a good file page when get_user_pages_fast * found it, but truncated or holepunched or subjected to * invalidate_complete_page2 before we got the folio lock (also * cases which we are happy to fail). And we hold a reference, * so refcount care in invalidate_inode_page's remove_mapping * prevents drop_caches from setting mapping to NULL beneath us. * * The case we do have to guard against is when memory pressure made * shmem_writepage move it from filecache to swapcache beneath us: * an unlikely race, but we do need to retry for folio->mapping. */ if (unlikely(!mapping)) { int shmem_swizzled; /* * Folio lock is required to identify which special case above * applies. If this is really a shmem page then the folio lock * will prevent unexpected transitions. */ folio_lock(folio); shmem_swizzled = folio_test_swapcache(folio) || folio->mapping; folio_unlock(folio); folio_put(folio); if (shmem_swizzled) goto again; return -EFAULT; } /* * Private mappings are handled in a simple way. * * If the futex key is stored in anonymous memory, then the associated * object is the mm which is implicitly pinned by the calling process. * * NOTE: When userspace waits on a MAP_SHARED mapping, even if * it's a read-only handle, it's expected that futexes attach to * the object not the particular process. */ if (folio_test_anon(folio)) { /* * A RO anonymous page will never change and thus doesn't make * sense for futex operations. */ if (unlikely(should_fail_futex(true)) || ro) { err = -EFAULT; goto out; } key->both.offset |= FUT_OFF_MMSHARED; /* ref taken on mm */ key->private.mm = mm; key->private.address = address; } else { struct inode *inode; /* * The associated futex object in this case is the inode and * the folio->mapping must be traversed. Ordinarily this should * be stabilised under folio lock but it's not strictly * necessary in this case as we just want to pin the inode, not * update i_pages or anything like that. * * The RCU read lock is taken as the inode is finally freed * under RCU. If the mapping still matches expectations then the * mapping->host can be safely accessed as being a valid inode. */ rcu_read_lock(); if (READ_ONCE(folio->mapping) != mapping) { rcu_read_unlock(); folio_put(folio); goto again; } inode = READ_ONCE(mapping->host); if (!inode) { rcu_read_unlock(); folio_put(folio); goto again; } key->both.offset |= FUT_OFF_INODE; /* inode-based key */ key->shared.i_seq = get_inode_sequence_number(inode); key->shared.pgoff = page_pgoff(folio, page); rcu_read_unlock(); } out: folio_put(folio); return err; } /** * fault_in_user_writeable() - Fault in user address and verify RW access * @uaddr: pointer to faulting user space address * * Slow path to fixup the fault we just took in the atomic write * access to @uaddr. * * We have no generic implementation of a non-destructive write to the * user address. We know that we faulted in the atomic pagefault * disabled section so we can as well avoid the #PF overhead by * calling get_user_pages() right away. */ int fault_in_user_writeable(u32 __user *uaddr) { struct mm_struct *mm = current->mm; int ret; mmap_read_lock(mm); ret = fixup_user_fault(mm, (unsigned long)uaddr, FAULT_FLAG_WRITE, NULL); mmap_read_unlock(mm); return ret < 0 ? ret : 0; } /** * futex_top_waiter() - Return the highest priority waiter on a futex * @hb: the hash bucket the futex_q's reside in * @key: the futex key (to distinguish it from other futex futex_q's) * * Must be called with the hb lock held. */ struct futex_q *futex_top_waiter(struct futex_hash_bucket *hb, union futex_key *key) { struct futex_q *this; plist_for_each_entry(this, &hb->chain, list) { if (futex_match(&this->key, key)) return this; } return NULL; } /** * wait_for_owner_exiting - Block until the owner has exited * @ret: owner's current futex lock status * @exiting: Pointer to the exiting task * * Caller must hold a refcount on @exiting. */ void wait_for_owner_exiting(int ret, struct task_struct *exiting) { if (ret != -EBUSY) { WARN_ON_ONCE(exiting); return; } if (WARN_ON_ONCE(ret == -EBUSY && !exiting)) return; mutex_lock(&exiting->futex_exit_mutex); /* * No point in doing state checking here. If the waiter got here * while the task was in exec()->exec_futex_release() then it can * have any FUTEX_STATE_* value when the waiter has acquired the * mutex. OK, if running, EXITING or DEAD if it reached exit() * already. Highly unlikely and not a problem. Just one more round * through the futex maze. */ mutex_unlock(&exiting->futex_exit_mutex); put_task_struct(exiting); } /** * __futex_unqueue() - Remove the futex_q from its futex_hash_bucket * @q: The futex_q to unqueue * * The q->lock_ptr must not be NULL and must be held by the caller. */ void __futex_unqueue(struct futex_q *q) { struct futex_hash_bucket *hb; if (WARN_ON_SMP(!q->lock_ptr) || WARN_ON(plist_node_empty(&q->list))) return; lockdep_assert_held(q->lock_ptr); hb = container_of(q->lock_ptr, struct futex_hash_bucket, lock); plist_del(&q->list, &hb->chain); futex_hb_waiters_dec(hb); } /* The key must be already stored in q->key. */ void futex_q_lock(struct futex_q *q, struct futex_hash_bucket *hb) __acquires(&hb->lock) { /* * Increment the counter before taking the lock so that * a potential waker won't miss a to-be-slept task that is * waiting for the spinlock. This is safe as all futex_q_lock() * users end up calling futex_queue(). Similarly, for housekeeping, * decrement the counter at futex_q_unlock() when some error has * occurred and we don't end up adding the task to the list. */ futex_hb_waiters_inc(hb); /* implies smp_mb(); (A) */ q->lock_ptr = &hb->lock; spin_lock(&hb->lock); } void futex_q_unlock(struct futex_hash_bucket *hb) __releases(&hb->lock) { futex_hb_waiters_dec(hb); spin_unlock(&hb->lock); } void __futex_queue(struct futex_q *q, struct futex_hash_bucket *hb, struct task_struct *task) { int prio; /* * The priority used to register this element is * - either the real thread-priority for the real-time threads * (i.e. threads with a priority lower than MAX_RT_PRIO) * - or MAX_RT_PRIO for non-RT threads. * Thus, all RT-threads are woken first in priority order, and * the others are woken last, in FIFO order. */ prio = min(current->normal_prio, MAX_RT_PRIO); plist_node_init(&q->list, prio); plist_add(&q->list, &hb->chain); q->task = task; } /** * futex_unqueue() - Remove the futex_q from its futex_hash_bucket * @q: The futex_q to unqueue * * The q->lock_ptr must not be held by the caller. A call to futex_unqueue() must * be paired with exactly one earlier call to futex_queue(). * * Return: * - 1 - if the futex_q was still queued (and we removed unqueued it); * - 0 - if the futex_q was already removed by the waking thread */ int futex_unqueue(struct futex_q *q) { spinlock_t *lock_ptr; int ret = 0; /* RCU so lock_ptr is not going away during locking. */ guard(rcu)(); /* In the common case we don't take the spinlock, which is nice. */ retry: /* * q->lock_ptr can change between this read and the following spin_lock. * Use READ_ONCE to forbid the compiler from reloading q->lock_ptr and * optimizing lock_ptr out of the logic below. */ lock_ptr = READ_ONCE(q->lock_ptr); if (lock_ptr != NULL) { spin_lock(lock_ptr); /* * q->lock_ptr can change between reading it and * spin_lock(), causing us to take the wrong lock. This * corrects the race condition. * * Reasoning goes like this: if we have the wrong lock, * q->lock_ptr must have changed (maybe several times) * between reading it and the spin_lock(). It can * change again after the spin_lock() but only if it was * already changed before the spin_lock(). It cannot, * however, change back to the original value. Therefore * we can detect whether we acquired the correct lock. */ if (unlikely(lock_ptr != q->lock_ptr)) { spin_unlock(lock_ptr); goto retry; } __futex_unqueue(q); BUG_ON(q->pi_state); spin_unlock(lock_ptr); ret = 1; } return ret; } void futex_q_lockptr_lock(struct futex_q *q) { spinlock_t *lock_ptr; /* * See futex_unqueue() why lock_ptr can change. */ guard(rcu)(); retry: lock_ptr = READ_ONCE(q->lock_ptr); spin_lock(lock_ptr); if (unlikely(lock_ptr != q->lock_ptr)) { spin_unlock(lock_ptr); goto retry; } } /* * PI futexes can not be requeued and must remove themselves from the hash * bucket. The hash bucket lock (i.e. lock_ptr) is held. */ void futex_unqueue_pi(struct futex_q *q) { /* * If the lock was not acquired (due to timeout or signal) then the * rt_waiter is removed before futex_q is. If this is observed by * an unlocker after dropping the rtmutex wait lock and before * acquiring the hash bucket lock, then the unlocker dequeues the * futex_q from the hash bucket list to guarantee consistent state * vs. userspace. Therefore the dequeue here must be conditional. */ if (!plist_node_empty(&q->list)) __futex_unqueue(q); BUG_ON(!q->pi_state); put_pi_state(q->pi_state); q->pi_state = NULL; } /* Constants for the pending_op argument of handle_futex_death */ #define HANDLE_DEATH_PENDING true #define HANDLE_DEATH_LIST false /* * Process a futex-list entry, check whether it's owned by the * dying task, and do notification if so: */ static int handle_futex_death(u32 __user *uaddr, struct task_struct *curr, bool pi, bool pending_op) { u32 uval, nval, mval; pid_t owner; int err; /* Futex address must be 32bit aligned */ if ((((unsigned long)uaddr) % sizeof(*uaddr)) != 0) return -1; retry: if (get_user(uval, uaddr)) return -1; /* * Special case for regular (non PI) futexes. The unlock path in * user space has two race scenarios: * * 1. The unlock path releases the user space futex value and * before it can execute the futex() syscall to wake up * waiters it is killed. * * 2. A woken up waiter is killed before it can acquire the * futex in user space. * * In the second case, the wake up notification could be generated * by the unlock path in user space after setting the futex value * to zero or by the kernel after setting the OWNER_DIED bit below. * * In both cases the TID validation below prevents a wakeup of * potential waiters which can cause these waiters to block * forever. * * In both cases the following conditions are met: * * 1) task->robust_list->list_op_pending != NULL * @pending_op == true * 2) The owner part of user space futex value == 0 * 3) Regular futex: @pi == false * * If these conditions are met, it is safe to attempt waking up a * potential waiter without touching the user space futex value and * trying to set the OWNER_DIED bit. If the futex value is zero, * the rest of the user space mutex state is consistent, so a woken * waiter will just take over the uncontended futex. Setting the * OWNER_DIED bit would create inconsistent state and malfunction * of the user space owner died handling. Otherwise, the OWNER_DIED * bit is already set, and the woken waiter is expected to deal with * this. */ owner = uval & FUTEX_TID_MASK; if (pending_op && !pi && !owner) { futex_wake(uaddr, FLAGS_SIZE_32 | FLAGS_SHARED, 1, FUTEX_BITSET_MATCH_ANY); return 0; } if (owner != task_pid_vnr(curr)) return 0; /* * Ok, this dying thread is truly holding a futex * of interest. Set the OWNER_DIED bit atomically * via cmpxchg, and if the value had FUTEX_WAITERS * set, wake up a waiter (if any). (We have to do a * futex_wake() even if OWNER_DIED is already set - * to handle the rare but possible case of recursive * thread-death.) The rest of the cleanup is done in * userspace. */ mval = (uval & FUTEX_WAITERS) | FUTEX_OWNER_DIED; /* * We are not holding a lock here, but we want to have * the pagefault_disable/enable() protection because * we want to handle the fault gracefully. If the * access fails we try to fault in the futex with R/W * verification via get_user_pages. get_user() above * does not guarantee R/W access. If that fails we * give up and leave the futex locked. */ if ((err = futex_cmpxchg_value_locked(&nval, uaddr, uval, mval))) { switch (err) { case -EFAULT: if (fault_in_user_writeable(uaddr)) return -1; goto retry; case -EAGAIN: cond_resched(); goto retry; default: WARN_ON_ONCE(1); return err; } } if (nval != uval) goto retry; /* * Wake robust non-PI futexes here. The wakeup of * PI futexes happens in exit_pi_state(): */ if (!pi && (uval & FUTEX_WAITERS)) { futex_wake(uaddr, FLAGS_SIZE_32 | FLAGS_SHARED, 1, FUTEX_BITSET_MATCH_ANY); } return 0; } /* * Fetch a robust-list pointer. Bit 0 signals PI futexes: */ static inline int fetch_robust_entry(struct robust_list __user **entry, struct robust_list __user * __user *head, unsigned int *pi) { unsigned long uentry; if (get_user(uentry, (unsigned long __user *)head)) return -EFAULT; *entry = (void __user *)(uentry & ~1UL); *pi = uentry & 1; return 0; } /* * Walk curr->robust_list (very carefully, it's a userspace list!) * and mark any locks found there dead, and notify any waiters. * * We silently return on any sign of list-walking problem. */ static void exit_robust_list(struct task_struct *curr) { struct robust_list_head __user *head = curr->robust_list; struct robust_list __user *entry, *next_entry, *pending; unsigned int limit = ROBUST_LIST_LIMIT, pi, pip; unsigned int next_pi; unsigned long futex_offset; int rc; /* * Fetch the list head (which was registered earlier, via * sys_set_robust_list()): */ if (fetch_robust_entry(&entry, &head->list.next, &pi)) return; /* * Fetch the relative futex offset: */ if (get_user(futex_offset, &head->futex_offset)) return; /* * Fetch any possibly pending lock-add first, and handle it * if it exists: */ if (fetch_robust_entry(&pending, &head->list_op_pending, &pip)) return; next_entry = NULL; /* avoid warning with gcc */ while (entry != &head->list) { /* * Fetch the next entry in the list before calling * handle_futex_death: */ rc = fetch_robust_entry(&next_entry, &entry->next, &next_pi); /* * A pending lock might already be on the list, so * don't process it twice: */ if (entry != pending) { if (handle_futex_death((void __user *)entry + futex_offset, curr, pi, HANDLE_DEATH_LIST)) return; } if (rc) return; entry = next_entry; pi = next_pi; /* * Avoid excessively long or circular lists: */ if (!--limit) break; cond_resched(); } if (pending) { handle_futex_death((void __user *)pending + futex_offset, curr, pip, HANDLE_DEATH_PENDING); } } #ifdef CONFIG_COMPAT static void __user *futex_uaddr(struct robust_list __user *entry, compat_long_t futex_offset) { compat_uptr_t base = ptr_to_compat(entry); void __user *uaddr = compat_ptr(base + futex_offset); return uaddr; } /* * Fetch a robust-list pointer. Bit 0 signals PI futexes: */ static inline int compat_fetch_robust_entry(compat_uptr_t *uentry, struct robust_list __user **entry, compat_uptr_t __user *head, unsigned int *pi) { if (get_user(*uentry, head)) return -EFAULT; *entry = compat_ptr((*uentry) & ~1); *pi = (unsigned int)(*uentry) & 1; return 0; } /* * Walk curr->robust_list (very carefully, it's a userspace list!) * and mark any locks found there dead, and notify any waiters. * * We silently return on any sign of list-walking problem. */ static void compat_exit_robust_list(struct task_struct *curr) { struct compat_robust_list_head __user *head = curr->compat_robust_list; struct robust_list __user *entry, *next_entry, *pending; unsigned int limit = ROBUST_LIST_LIMIT, pi, pip; unsigned int next_pi; compat_uptr_t uentry, next_uentry, upending; compat_long_t futex_offset; int rc; /* * Fetch the list head (which was registered earlier, via * sys_set_robust_list()): */ if (compat_fetch_robust_entry(&uentry, &entry, &head->list.next, &pi)) return; /* * Fetch the relative futex offset: */ if (get_user(futex_offset, &head->futex_offset)) return; /* * Fetch any possibly pending lock-add first, and handle it * if it exists: */ if (compat_fetch_robust_entry(&upending, &pending, &head->list_op_pending, &pip)) return; next_entry = NULL; /* avoid warning with gcc */ while (entry != (struct robust_list __user *) &head->list) { /* * Fetch the next entry in the list before calling * handle_futex_death: */ rc = compat_fetch_robust_entry(&next_uentry, &next_entry, (compat_uptr_t __user *)&entry->next, &next_pi); /* * A pending lock might already be on the list, so * dont process it twice: */ if (entry != pending) { void __user *uaddr = futex_uaddr(entry, futex_offset); if (handle_futex_death(uaddr, curr, pi, HANDLE_DEATH_LIST)) return; } if (rc) return; uentry = next_uentry; entry = next_entry; pi = next_pi; /* * Avoid excessively long or circular lists: */ if (!--limit) break; cond_resched(); } if (pending) { void __user *uaddr = futex_uaddr(pending, futex_offset); handle_futex_death(uaddr, curr, pip, HANDLE_DEATH_PENDING); } } #endif #ifdef CONFIG_FUTEX_PI /* * This task is holding PI mutexes at exit time => bad. * Kernel cleans up PI-state, but userspace is likely hosed. * (Robust-futex cleanup is separate and might save the day for userspace.) */ static void exit_pi_state_list(struct task_struct *curr) { struct list_head *next, *head = &curr->pi_state_list; struct futex_pi_state *pi_state; union futex_key key = FUTEX_KEY_INIT; /* * The mutex mm_struct::futex_hash_lock might be acquired. */ might_sleep(); /* * Ensure the hash remains stable (no resize) during the while loop * below. The hb pointer is acquired under the pi_lock so we can't block * on the mutex. */ WARN_ON(curr != current); guard(private_hash)(); /* * We are a ZOMBIE and nobody can enqueue itself on * pi_state_list anymore, but we have to be careful * versus waiters unqueueing themselves: */ raw_spin_lock_irq(&curr->pi_lock); while (!list_empty(head)) { next = head->next; pi_state = list_entry(next, struct futex_pi_state, list); key = pi_state->key; if (1) { CLASS(hb, hb)(&key); /* * We can race against put_pi_state() removing itself from the * list (a waiter going away). put_pi_state() will first * decrement the reference count and then modify the list, so * its possible to see the list entry but fail this reference * acquire. * * In that case; drop the locks to let put_pi_state() make * progress and retry the loop. */ if (!refcount_inc_not_zero(&pi_state->refcount)) { raw_spin_unlock_irq(&curr->pi_lock); cpu_relax(); raw_spin_lock_irq(&curr->pi_lock); continue; } raw_spin_unlock_irq(&curr->pi_lock); spin_lock(&hb->lock); raw_spin_lock_irq(&pi_state->pi_mutex.wait_lock); raw_spin_lock(&curr->pi_lock); /* * We dropped the pi-lock, so re-check whether this * task still owns the PI-state: */ if (head->next != next) { /* retain curr->pi_lock for the loop invariant */ raw_spin_unlock(&pi_state->pi_mutex.wait_lock); spin_unlock(&hb->lock); put_pi_state(pi_state); continue; } WARN_ON(pi_state->owner != curr); WARN_ON(list_empty(&pi_state->list)); list_del_init(&pi_state->list); pi_state->owner = NULL; raw_spin_unlock(&curr->pi_lock); raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock); spin_unlock(&hb->lock); } rt_mutex_futex_unlock(&pi_state->pi_mutex); put_pi_state(pi_state); raw_spin_lock_irq(&curr->pi_lock); } raw_spin_unlock_irq(&curr->pi_lock); } #else static inline void exit_pi_state_list(struct task_struct *curr) { } #endif static void futex_cleanup(struct task_struct *tsk) { if (unlikely(tsk->robust_list)) { exit_robust_list(tsk); tsk->robust_list = NULL; } #ifdef CONFIG_COMPAT if (unlikely(tsk->compat_robust_list)) { compat_exit_robust_list(tsk); tsk->compat_robust_list = NULL; } #endif if (unlikely(!list_empty(&tsk->pi_state_list))) exit_pi_state_list(tsk); } /** * futex_exit_recursive - Set the tasks futex state to FUTEX_STATE_DEAD * @tsk: task to set the state on * * Set the futex exit state of the task lockless. The futex waiter code * observes that state when a task is exiting and loops until the task has * actually finished the futex cleanup. The worst case for this is that the * waiter runs through the wait loop until the state becomes visible. * * This is called from the recursive fault handling path in make_task_dead(). * * This is best effort. Either the futex exit code has run already or * not. If the OWNER_DIED bit has been set on the futex then the waiter can * take it over. If not, the problem is pushed back to user space. If the * futex exit code did not run yet, then an already queued waiter might * block forever, but there is nothing which can be done about that. */ void futex_exit_recursive(struct task_struct *tsk) { /* If the state is FUTEX_STATE_EXITING then futex_exit_mutex is held */ if (tsk->futex_state == FUTEX_STATE_EXITING) mutex_unlock(&tsk->futex_exit_mutex); tsk->futex_state = FUTEX_STATE_DEAD; } static void futex_cleanup_begin(struct task_struct *tsk) { /* * Prevent various race issues against a concurrent incoming waiter * including live locks by forcing the waiter to block on * tsk->futex_exit_mutex when it observes FUTEX_STATE_EXITING in * attach_to_pi_owner(). */ mutex_lock(&tsk->futex_exit_mutex); /* * Switch the state to FUTEX_STATE_EXITING under tsk->pi_lock. * * This ensures that all subsequent checks of tsk->futex_state in * attach_to_pi_owner() must observe FUTEX_STATE_EXITING with * tsk->pi_lock held. * * It guarantees also that a pi_state which was queued right before * the state change under tsk->pi_lock by a concurrent waiter must * be observed in exit_pi_state_list(). */ raw_spin_lock_irq(&tsk->pi_lock); tsk->futex_state = FUTEX_STATE_EXITING; raw_spin_unlock_irq(&tsk->pi_lock); } static void futex_cleanup_end(struct task_struct *tsk, int state) { /* * Lockless store. The only side effect is that an observer might * take another loop until it becomes visible. */ tsk->futex_state = state; /* * Drop the exit protection. This unblocks waiters which observed * FUTEX_STATE_EXITING to reevaluate the state. */ mutex_unlock(&tsk->futex_exit_mutex); } void futex_exec_release(struct task_struct *tsk) { /* * The state handling is done for consistency, but in the case of * exec() there is no way to prevent further damage as the PID stays * the same. But for the unlikely and arguably buggy case that a * futex is held on exec(), this provides at least as much state * consistency protection which is possible. */ futex_cleanup_begin(tsk); futex_cleanup(tsk); /* * Reset the state to FUTEX_STATE_OK. The task is alive and about * exec a new binary. */ futex_cleanup_end(tsk, FUTEX_STATE_OK); } void futex_exit_release(struct task_struct *tsk) { futex_cleanup_begin(tsk); futex_cleanup(tsk); futex_cleanup_end(tsk, FUTEX_STATE_DEAD); } static void futex_hash_bucket_init(struct futex_hash_bucket *fhb, struct futex_private_hash *fph) { #ifdef CONFIG_FUTEX_PRIVATE_HASH fhb->priv = fph; #endif atomic_set(&fhb->waiters, 0); plist_head_init(&fhb->chain); spin_lock_init(&fhb->lock); } #define FH_CUSTOM 0x01 #define FH_IMMUTABLE 0x02 #ifdef CONFIG_FUTEX_PRIVATE_HASH void futex_hash_free(struct mm_struct *mm) { struct futex_private_hash *fph; kvfree(mm->futex_phash_new); fph = rcu_dereference_raw(mm->futex_phash); if (fph) { WARN_ON_ONCE(rcuref_read(&fph->users) > 1); kvfree(fph); } } static bool futex_pivot_pending(struct mm_struct *mm) { struct futex_private_hash *fph; guard(rcu)(); if (!mm->futex_phash_new) return true; fph = rcu_dereference(mm->futex_phash); return rcuref_is_dead(&fph->users); } static bool futex_hash_less(struct futex_private_hash *a, struct futex_private_hash *b) { /* user provided always wins */ if (!a->custom && b->custom) return true; if (a->custom && !b->custom) return false; /* zero-sized hash wins */ if (!b->hash_mask) return true; if (!a->hash_mask) return false; /* keep the biggest */ if (a->hash_mask < b->hash_mask) return true; if (a->hash_mask > b->hash_mask) return false; return false; /* equal */ } static int futex_hash_allocate(unsigned int hash_slots, unsigned int flags) { struct mm_struct *mm = current->mm; struct futex_private_hash *fph; bool custom = flags & FH_CUSTOM; int i; if (hash_slots && (hash_slots == 1 || !is_power_of_2(hash_slots))) return -EINVAL; /* * Once we've disabled the global hash there is no way back. */ scoped_guard(rcu) { fph = rcu_dereference(mm->futex_phash); if (fph && (!fph->hash_mask || fph->immutable)) { if (custom) return -EBUSY; return 0; } } fph = kvzalloc(struct_size(fph, queues, hash_slots), GFP_KERNEL_ACCOUNT | __GFP_NOWARN); if (!fph) return -ENOMEM; rcuref_init(&fph->users, 1); fph->hash_mask = hash_slots ? hash_slots - 1 : 0; fph->custom = custom; fph->immutable = !!(flags & FH_IMMUTABLE); fph->mm = mm; for (i = 0; i < hash_slots; i++) futex_hash_bucket_init(&fph->queues[i], fph); if (custom) { /* * Only let prctl() wait / retry; don't unduly delay clone(). */ again: wait_var_event(mm, futex_pivot_pending(mm)); } scoped_guard(mutex, &mm->futex_hash_lock) { struct futex_private_hash *free __free(kvfree) = NULL; struct futex_private_hash *cur, *new; cur = rcu_dereference_protected(mm->futex_phash, lockdep_is_held(&mm->futex_hash_lock)); new = mm->futex_phash_new; mm->futex_phash_new = NULL; if (fph) { if (cur && (!cur->hash_mask || cur->immutable)) { /* * If two threads simultaneously request the global * hash then the first one performs the switch, * the second one returns here. */ free = fph; mm->futex_phash_new = new; return -EBUSY; } if (cur && !new) { /* * If we have an existing hash, but do not yet have * allocated a replacement hash, drop the initial * reference on the existing hash. */ futex_private_hash_put(cur); } if (new) { /* * Two updates raced; throw out the lesser one. */ if (futex_hash_less(new, fph)) { free = new; new = fph; } else { free = fph; } } else { new = fph; } fph = NULL; } if (new) { /* * Will set mm->futex_phash_new on failure; * futex_private_hash_get() will try again. */ if (!__futex_pivot_hash(mm, new) && custom) goto again; } } return 0; } int futex_hash_allocate_default(void) { unsigned int threads, buckets, current_buckets = 0; struct futex_private_hash *fph; if (!current->mm) return 0; scoped_guard(rcu) { threads = min_t(unsigned int, get_nr_threads(current), num_online_cpus()); fph = rcu_dereference(current->mm->futex_phash); if (fph) { if (fph->custom) return 0; current_buckets = fph->hash_mask + 1; } } /* * The default allocation will remain within * 16 <= threads * 4 <= global hash size */ buckets = roundup_pow_of_two(4 * threads); buckets = clamp(buckets, 16, futex_hashmask + 1); if (current_buckets >= buckets) return 0; return futex_hash_allocate(buckets, 0); } static int futex_hash_get_slots(void) { struct futex_private_hash *fph; guard(rcu)(); fph = rcu_dereference(current->mm->futex_phash); if (fph && fph->hash_mask) return fph->hash_mask + 1; return 0; } static int futex_hash_get_immutable(void) { struct futex_private_hash *fph; guard(rcu)(); fph = rcu_dereference(current->mm->futex_phash); if (fph && fph->immutable) return 1; if (fph && !fph->hash_mask) return 1; return 0; } #else static int futex_hash_allocate(unsigned int hash_slots, unsigned int flags) { return -EINVAL; } static int futex_hash_get_slots(void) { return 0; } static int futex_hash_get_immutable(void) { return 0; } #endif int futex_hash_prctl(unsigned long arg2, unsigned long arg3, unsigned long arg4) { unsigned int flags = FH_CUSTOM; int ret; switch (arg2) { case PR_FUTEX_HASH_SET_SLOTS: if (arg4 & ~FH_FLAG_IMMUTABLE) return -EINVAL; if (arg4 & FH_FLAG_IMMUTABLE) flags |= FH_IMMUTABLE; ret = futex_hash_allocate(arg3, flags); break; case PR_FUTEX_HASH_GET_SLOTS: ret = futex_hash_get_slots(); break; case PR_FUTEX_HASH_GET_IMMUTABLE: ret = futex_hash_get_immutable(); break; default: ret = -EINVAL; break; } return ret; } static int __init futex_init(void) { unsigned long hashsize, i; unsigned int order, n; unsigned long size; #ifdef CONFIG_BASE_SMALL hashsize = 16; #else hashsize = 256 * num_possible_cpus(); hashsize /= num_possible_nodes(); hashsize = max(4, hashsize); hashsize = roundup_pow_of_two(hashsize); #endif futex_hashshift = ilog2(hashsize); size = sizeof(struct futex_hash_bucket) * hashsize; order = get_order(size); for_each_node(n) { struct futex_hash_bucket *table; if (order > MAX_PAGE_ORDER) table = vmalloc_huge_node(size, GFP_KERNEL, n); else table = alloc_pages_exact_nid(n, size, GFP_KERNEL); BUG_ON(!table); for (i = 0; i < hashsize; i++) futex_hash_bucket_init(&table[i], NULL); futex_queues[n] = table; } futex_hashmask = hashsize - 1; pr_info("futex hash table entries: %lu (%lu bytes on %d NUMA nodes, total %lu KiB, %s).\n", hashsize, size, num_possible_nodes(), size * num_possible_nodes() / 1024, order > MAX_PAGE_ORDER ? "vmalloc" : "linear"); return 0; } core_initcall(futex_init);
Information contained on this website is for historical information purposes only and does not indicate or represent copyright ownership.
Created with Cregit http://github.com/cregit/cregit
Version 2.0-RC1