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McKenney" To: rcu@vger.kernel.org, linux-kernel@vger.kernel.org Cc: kernel-team@meta.com, Mathieu Desnoyers , Boqun Feng , Steven Rostedt , lkmm@lists.linux.dev, Zqiang , Wang Lian , Kunwu Chan , Bradley Morgan , Nicholas Piggin , Michael Ellerman , Greg Kroah-Hartman , Sebastian Andrzej Siewior , "Paul E. McKenney" , Will Deacon , Peter Zijlstra , Alan Stern , John Stultz , Linus Torvalds , Andrew Morton , Frederic Weisbecker , Joel Fernandes , Josh Triplett , Uladzislau Rezki , Lai Jiangshan , Zqiang , Ingo Molnar , Waiman Long , Mark Rutland , Thomas Gleixner , Vlastimil Babka , maged.michael@gmail.com, Mateusz Guzik , Jonas Oberhauser , linux-mm@kvack.org Subject: [PATCH 01/28] hazptr: Implement Hazard Pointers Date: Fri, 18 Sep 2026 17:00:29 -0700 Message-Id: <20260919000056.3132131-1-paulmck@kernel.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Queue-Id: ACD0240003 X-Stat-Signature: 4b6wftnyfwezz1yy9onz7zr1g45t7jwk X-Rspamd-Server: rspam01 X-HE-Tag: 1789776060-217556 X-HE-Meta: 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 rDPJU7Ch 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 SzmlIljM Lkw0+T9sug3LxU/OROqvIHjP/1xfdDn2dKdIYHJE+kdM4BGnR2nVRJFqaEMI/s0vxjMCW9FTnmvLHe61il8FBq5eFPdNc8yWtou3YDZi62u2zFp50JUOhNbj0lzhxO2AXqUQFhQAr3mwAhQe4E2eC6MF1yUd45ChdokJhgMkpyRlTzbFKEuBXs5aKxt10nRn2Z5+zK165UowIRWu5IpZxFsV5WvW/jLFX3dvBa3yJJqSC/+iVhNfk0w5zmbgcfHAO/1/Cgt56Ps= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Mathieu Desnoyers This API provides existence guarantees of objects through Hazard Pointers [1] (hazptr). Its main benefit over RCU is that it allows fast reclaim of HP-protected pointers without needing to wait for a grace period. This implementation has 4 statically allocated hazard pointer slots per cpu for the fast path, and relies on a on-stack backup slot allocated by the hazard pointer user as fallback in case no per-cpu slot is available. It integrates with the scheduler to migrate per-CPU slots to the backup slot on context switch. This ensures that the per-CPU slots won't be used by blocked or preempted tasks holding on hazard pointers for a long time. References: [1]: M. M. Michael, "Hazard pointers: safe memory reclamation for lock-free objects," in IEEE Transactions on Parallel and Distributed Systems, vol. 15, no. 6, pp. 491-504, June 2004 Link: https://lpc.events/event/19/contributions/2082/ Link: https://lore.kernel.org/lkml/j3scdl5iymjlxavomgc6u5ndg3svhab6ga23dr36o4f5mt333w@7xslvq6b6hmv/ Link: https://lpc.events/event/18/contributions/1731/ Signed-off-by: Mathieu Desnoyers Cc: Nicholas Piggin Cc: Michael Ellerman Cc: Greg Kroah-Hartman Cc: Sebastian Andrzej Siewior Cc: "Paul E. McKenney" Cc: Will Deacon Cc: Peter Zijlstra Cc: Boqun Feng Cc: Alan Stern Cc: John Stultz Cc: Linus Torvalds Cc: Andrew Morton Cc: Frederic Weisbecker Cc: Joel Fernandes Cc: Josh Triplett Cc: Uladzislau Rezki Cc: Steven Rostedt Cc: Lai Jiangshan Cc: Zqiang Cc: Ingo Molnar Cc: Waiman Long Cc: Mark Rutland Cc: Thomas Gleixner Cc: Vlastimil Babka Cc: maged.michael@gmail.com Cc: Mateusz Guzik Cc: Jonas Oberhauser Cc: Cc: Cc: Signed-off-by: Paul E. McKenney --- include/linux/hazptr.h | 197 +++++++++++++++++++++++++++++++++ init/main.c | 2 + kernel/Makefile | 2 +- kernel/hazptr.c | 242 +++++++++++++++++++++++++++++++++++++++++ kernel/sched/core.c | 2 + 5 files changed, 444 insertions(+), 1 deletion(-) create mode 100644 include/linux/hazptr.h create mode 100644 kernel/hazptr.c diff --git a/include/linux/hazptr.h b/include/linux/hazptr.h new file mode 100644 index 000000000000..b121f7779cda --- /dev/null +++ b/include/linux/hazptr.h @@ -0,0 +1,197 @@ +// SPDX-License-Identifier: LGPL-2.1-or-later +// +// SPDX-FileCopyrightText: 2024 Mathieu Desnoyers + +#ifndef _LINUX_HAZPTR_H +#define _LINUX_HAZPTR_H + +/* + * hazptr: Hazard Pointers + * + * This API provides existence guarantees of objects through hazard + * pointers. + * + * Its main benefit over RCU is that it allows fast reclaim of + * HP-protected pointers without needing to wait for a grace period. + * + * References: + * + * [1]: M. M. Michael, "Hazard pointers: safe memory reclamation for + * lock-free objects," in IEEE Transactions on Parallel and + * Distributed Systems, vol. 15, no. 6, pp. 491-504, June 2004 + */ + +#include +#include +#include +#include + +/* 4 slots (each sizeof(hazptr_slot_item)) fit in a single 64-byte cache line. */ +#define NR_HAZPTR_PERCPU_SLOTS 4 +#define HAZPTR_WILDCARD ((void *) 0x1UL) + +/* + * Hazard pointer slot. + */ +struct hazptr_slot { + void *addr; +}; + +struct hazptr_overflow_list; + +struct hazptr_backup_slot { + struct hlist_node overflow_node; + struct hazptr_slot slot; + /* Overflow list where the backup slot is added. */ + struct hazptr_overflow_list *overflow_list; +}; + +struct hazptr_ctx { + struct hazptr_slot *slot; + /* Backup slot in case all per-CPU slots are used. */ + struct hazptr_backup_slot backup_slot; + struct hlist_node preempt_node; +}; + +struct hazptr_slot_ctx { + struct hazptr_ctx *ctx; +}; + +struct hazptr_slot_item { + struct hazptr_slot slot; + struct hazptr_slot_ctx ctx; +}; + +struct hazptr_percpu_slots { + struct hazptr_slot_item items[NR_HAZPTR_PERCPU_SLOTS]; +} ____cacheline_aligned; + +DECLARE_PER_CPU(struct hazptr_percpu_slots, hazptr_percpu_slots); + +void *__hazptr_acquire(struct hazptr_ctx *ctx, void * const *addr_p); + +/* + * hazptr_synchronize: Wait until @addr is released from all slots. + * + * Wait to observe that each slot contains a value that differs from + * @addr before returning. + * Should be called from preemptible context. + */ +void hazptr_synchronize(void *addr); + +/* + * hazptr_chain_backup_slot: Chain backup slot into overflow list. + * + * Set backup slot address to @addr, and chain it into the overflow + * list. + */ +struct hazptr_slot *hazptr_chain_backup_slot(struct hazptr_ctx *ctx); + +/* + * hazptr_unchain_backup_slot: Unchain backup slot from overflow list. + */ +void hazptr_unchain_backup_slot(struct hazptr_ctx *ctx); + +static inline +bool hazptr_slot_is_backup(struct hazptr_ctx *ctx, struct hazptr_slot *slot) +{ + return slot == &ctx->backup_slot.slot; +} + +static inline +void hazptr_note_context_switch(void) +{ + struct hazptr_percpu_slots *percpu_slots = this_cpu_ptr(&hazptr_percpu_slots); + unsigned int idx; + + for (idx = 0; idx < NR_HAZPTR_PERCPU_SLOTS; idx++) { + struct hazptr_slot_item *item = &percpu_slots->items[idx]; + struct hazptr_slot *slot = &item->slot, *backup_slot; + struct hazptr_ctx *ctx; + + if (!slot->addr) + continue; + ctx = item->ctx.ctx; + backup_slot = hazptr_chain_backup_slot(ctx); + /* + * Move hazard pointer from the per-CPU slot to the + * backup slot. This requires hazard pointer + * synchronize to iterate on per-CPU slots with + * load-acquire before iterating on the overflow list. + */ + WRITE_ONCE(backup_slot->addr, slot->addr); + /* + * store-release orders store to backup slot addr before + * store to per-CPU slot addr. + */ + smp_store_release(&slot->addr, NULL); + /* Use the backup slot for context. */ + ctx->slot = backup_slot; + } +} + +/* + * hazptr_acquire: Load pointer at address and protect with hazard pointer. + * + * Load @addr_p, and protect the loaded pointer with hazard pointer. + * When using hazptr_acquire from interrupt handlers, the acquired slots + * need to be released before returning from the interrupt handler. + * + * Returns a non-NULL protected address if the loaded pointer is non-NULL. + * Returns NULL if the loaded pointer is NULL. + * + * On success the protected hazptr slot is stored in @ctx->slot. + */ +static inline +void *hazptr_acquire(struct hazptr_ctx *ctx, void * const *addr_p) +{ + struct hazptr_percpu_slots *percpu_slots; + struct hazptr_slot_item *slot_item; + struct hazptr_slot *slot; + void *addr; + + guard(preempt)(); + percpu_slots = this_cpu_ptr(&hazptr_percpu_slots); + slot_item = &percpu_slots->items[0]; + slot = &slot_item->slot; + if (unlikely(slot->addr)) + return __hazptr_acquire(ctx, addr_p); + WRITE_ONCE(slot->addr, HAZPTR_WILDCARD); /* Store B */ + + /* Memory ordering: Store B before Load A. */ + smp_mb(); + + /* + * Load @addr_p after storing wildcard to the hazard pointer slot. + */ + addr = READ_ONCE(*addr_p); /* Load A */ + + /* + * We don't care about ordering of Store C. It will simply + * replace the wildcard by a more specific address. If addr is + * NULL, we simply store NULL into the slot. + */ + WRITE_ONCE(slot->addr, addr); /* Store C */ + slot_item->ctx.ctx = ctx; + ctx->slot = slot; + return addr; +} + +/* Release the protected hazard pointer from @slot. */ +static inline +void hazptr_release(struct hazptr_ctx *ctx, void *addr) +{ + struct hazptr_slot *slot; + + if (!addr) + return; + guard(preempt)(); + slot = ctx->slot; + smp_store_release(&slot->addr, NULL); + if (unlikely(hazptr_slot_is_backup(ctx, slot))) + hazptr_unchain_backup_slot(ctx); +} + +void hazptr_init(void); + +#endif /* _LINUX_HAZPTR_H */ diff --git a/init/main.c b/init/main.c index 2613d3f9b3ce..d9d936707c19 100644 --- a/init/main.c +++ b/init/main.c @@ -108,6 +108,7 @@ #include #include #include +#include #include #include @@ -1075,6 +1076,7 @@ void start_kernel(void) workqueue_init_early(); rcu_init(); + hazptr_init(); kvfree_rcu_init(); /* Trace events are available after this */ diff --git a/kernel/Makefile b/kernel/Makefile index 1e1a31673577..8961c8660d0d 100644 --- a/kernel/Makefile +++ b/kernel/Makefile @@ -7,7 +7,7 @@ obj-y = fork.o exec_domain.o exec_state.o panic.o \ cpu.o exit.o softirq.o resource.o \ sysctl.o capability.o ptrace.o user.o \ signal.o sys.o umh.o workqueue.o pid.o task_work.o \ - extable.o params.o \ + extable.o params.o hazptr.o \ kthread.o sys_ni.o nsproxy.o nstree.o nscommon.o \ notifier.o ksysfs.o cred.o reboot.o \ async.o range.o smpboot.o ucount.o regset.o ksyms_common.o diff --git a/kernel/hazptr.c b/kernel/hazptr.c new file mode 100644 index 000000000000..a9d3d68a1525 --- /dev/null +++ b/kernel/hazptr.c @@ -0,0 +1,242 @@ +// SPDX-License-Identifier: LGPL-2.1-or-later +// +// SPDX-FileCopyrightText: 2024 Mathieu Desnoyers + +/* + * hazptr: Hazard Pointers + */ + +#include +#include +#include +#include +#include +#include + +struct hazptr_overflow_list { + raw_spinlock_t lock; /* Lock protecting overflow list and list generation. */ + struct hlist_head head; /* Overflow list head. */ + uint64_t gen; /* Overflow list generation. */ +}; + +/* + * Flip between two lists to guarantee list scan forward progress even + * with frequent generation counter increments. The list additions are + * always done on a different list than the one used for scan. The scan + * successively iterates on both lists. Therefore, only list removals + * can cause the iteration to retry, and the number of removals is + * limited to the number of list elements. + */ +struct hazptr_overflow_list_flip { + struct mutex lock; /* Mutex protecting add_idx from concurrent updates. */ + unsigned int add_idx; /* Index of current flip-list to add to. */ + struct hazptr_overflow_list array[2]; +}; + +static DEFINE_PER_CPU(struct hazptr_overflow_list_flip, percpu_overflow_list_flip); + +DEFINE_PER_CPU(struct hazptr_percpu_slots, hazptr_percpu_slots); +EXPORT_PER_CPU_SYMBOL_GPL(hazptr_percpu_slots); + +static +struct hazptr_slot *hazptr_get_free_percpu_slot(struct hazptr_ctx *ctx) +{ + struct hazptr_percpu_slots *percpu_slots = this_cpu_ptr(&hazptr_percpu_slots); + unsigned int idx; + + for (idx = 0; idx < NR_HAZPTR_PERCPU_SLOTS; idx++) { + struct hazptr_slot_item *item = &percpu_slots->items[idx]; + struct hazptr_slot *slot = &item->slot; + + if (!slot->addr) { + item->ctx.ctx = ctx; + return slot; + } + } + /* All slots are in use. */ + return NULL; +} + +/* + * Hazard pointer acquire slow path. + * Called with preemption disabled. + */ +void *__hazptr_acquire(struct hazptr_ctx *ctx, void * const *addr_p) +{ + struct hazptr_slot *slot = hazptr_get_free_percpu_slot(ctx); + void *addr; + + /* + * If all the per-CPU slots are already in use, fallback + * to the backup slot. + */ + if (unlikely(!slot)) + slot = hazptr_chain_backup_slot(ctx); + WRITE_ONCE(slot->addr, HAZPTR_WILDCARD); /* Store B */ + + /* Memory ordering: Store B before Load A. */ + smp_mb(); + + /* + * Load @addr_p after storing wildcard to the hazard pointer slot. + */ + addr = READ_ONCE(*addr_p); /* Load A */ + + /* + * We don't care about ordering of Store C. It will simply + * replace the wildcard by a more specific address. If addr is + * NULL, we simply store NULL into the slot. + */ + WRITE_ONCE(slot->addr, addr); /* Store C */ + ctx->slot = slot; + if (!addr && hazptr_slot_is_backup(ctx, slot)) + hazptr_unchain_backup_slot(ctx); + return addr; +} +EXPORT_SYMBOL_GPL(__hazptr_acquire); + +/* + * Perform piecewise iteration on overflow list waiting until "addr" is + * not present. Raw spinlock is released and taken between each list + * item and busy loop iteration. The overflow list generation is checked + * each time the lock is taken to validate that the list has not changed + * before resuming iteration or busy wait. If the generation has + * changed, retry the entire list traversal. + */ +static +void hazptr_synchronize_overflow_list(struct hazptr_overflow_list *overflow_list, void *addr) +{ + struct hazptr_backup_slot *backup_slot; + uint64_t snapshot_gen; + unsigned long flags; + + raw_spin_lock_irqsave(&overflow_list->lock, flags); +retry: + snapshot_gen = overflow_list->gen; + hlist_for_each_entry(backup_slot, &overflow_list->head, overflow_node) { + /* Busy-wait if node is found. */ + for (;;) { + void *load_addr = smp_load_acquire(&backup_slot->slot.addr); /* Load B */ + + if (load_addr != addr && load_addr != HAZPTR_WILDCARD) + break; + raw_spin_unlock_irqrestore(&overflow_list->lock, flags); + cpu_relax(); + raw_spin_lock_irqsave(&overflow_list->lock, flags); + if (overflow_list->gen != snapshot_gen) + goto retry; + } + raw_spin_unlock_irqrestore(&overflow_list->lock, flags); + /* + * Release raw spinlock, validate generation after + * re-acquiring the lock. + */ + raw_spin_lock_irqsave(&overflow_list->lock, flags); + if (overflow_list->gen != snapshot_gen) + goto retry; + } + raw_spin_unlock_irqrestore(&overflow_list->lock, flags); +} + +static +void hazptr_synchronize_cpu_slots(int cpu, void *addr) +{ + struct hazptr_percpu_slots *percpu_slots = per_cpu_ptr(&hazptr_percpu_slots, cpu); + unsigned int idx; + + for (idx = 0; idx < NR_HAZPTR_PERCPU_SLOTS; idx++) { + struct hazptr_slot_item *item = &percpu_slots->items[idx]; + + /* Busy-wait if node is found. */ + smp_cond_load_acquire(&item->slot.addr, VAL != addr && VAL != HAZPTR_WILDCARD); /* Load B */ + } +} + +/* + * hazptr_synchronize: Wait until @addr is released from all slots. + * + * Wait to observe that each slot contains a value that differs from + * @addr before returning. + * Should be called from preemptible context. + */ +void hazptr_synchronize(void *addr) +{ + int cpu; + + /* + * Busy-wait should only be done from preemptible context. + */ + lockdep_assert_preemption_enabled(); + + /* + * Store A precedes hazptr_scan(): it unpublishes addr (sets it to + * NULL or to a different value), and thus hides it from hazard + * pointer readers. + */ + if (!addr) + return; + /* Memory ordering: Store A before Load B. */ + smp_mb(); + /* Scan all CPUs slots. */ + for_each_possible_cpu(cpu) { + struct hazptr_overflow_list_flip *overflow_list_flip = per_cpu_ptr(&percpu_overflow_list_flip, cpu); + unsigned int scan_idx; + + /* Scan CPU slots. */ + hazptr_synchronize_cpu_slots(cpu, addr); + + /* + * Scan backup slots in percpu overflow lists. + * Forward progress is guaranteed by scanning one list + * while new elements are added into the other list. + */ + guard(mutex)(&overflow_list_flip->lock); + scan_idx = overflow_list_flip->add_idx ^ 1; + hazptr_synchronize_overflow_list(&overflow_list_flip->array[scan_idx], addr); + /* Flip current list. */ + WRITE_ONCE(overflow_list_flip->add_idx, scan_idx); + hazptr_synchronize_overflow_list(&overflow_list_flip->array[scan_idx ^ 1], addr); + } +} +EXPORT_SYMBOL_GPL(hazptr_synchronize); + +struct hazptr_slot *hazptr_chain_backup_slot(struct hazptr_ctx *ctx) +{ + struct hazptr_overflow_list_flip *overflow_list_flip = this_cpu_ptr(&percpu_overflow_list_flip); + unsigned int list_idx = READ_ONCE(overflow_list_flip->add_idx); + struct hazptr_overflow_list *overflow_list = &overflow_list_flip->array[list_idx]; + struct hazptr_slot *slot = &ctx->backup_slot.slot; + + slot->addr = NULL; + guard(raw_spinlock_irqsave)(&overflow_list->lock); + overflow_list->gen++; + hlist_add_head(&ctx->backup_slot.overflow_node, &overflow_list->head); + ctx->backup_slot.overflow_list = overflow_list; + return slot; +} +EXPORT_SYMBOL_GPL(hazptr_chain_backup_slot); + +void hazptr_unchain_backup_slot(struct hazptr_ctx *ctx) +{ + struct hazptr_overflow_list *overflow_list = ctx->backup_slot.overflow_list; + + guard(raw_spinlock_irqsave)(&overflow_list->lock); + overflow_list->gen++; + hlist_del(&ctx->backup_slot.overflow_node); +} +EXPORT_SYMBOL_GPL(hazptr_unchain_backup_slot); + +void __init hazptr_init(void) +{ + int cpu; + + for_each_possible_cpu(cpu) { + struct hazptr_overflow_list_flip *overflow_list_flip = per_cpu_ptr(&percpu_overflow_list_flip, cpu); + + mutex_init(&overflow_list_flip->lock); + for (int i = 0; i < 2; i++) { + raw_spin_lock_init(&overflow_list_flip->array[i].lock); + INIT_HLIST_HEAD(&overflow_list_flip->array[i].head); + } + } +} diff --git a/kernel/sched/core.c b/kernel/sched/core.c index f78275192036..b77152edafd9 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -59,6 +59,7 @@ #include #include #include +#include #include #include #include @@ -7123,6 +7124,7 @@ static void __sched notrace __schedule(int sched_mode) local_irq_disable(); rcu_note_context_switch(preempt); migrate_disable_switch(rq, prev); + hazptr_note_context_switch(); /* * Make sure that signal_pending_state()->signal_pending() below -- 2.40.1