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Wed, 02 Apr 2025 19:55:18 -0700 (PDT) From: Alexei Starovoitov To: bpf@vger.kernel.org, linux-mm@kvack.org Cc: torvalds@linux-foundation.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@kernel.org, akpm@linux-foundation.org, peterz@infradead.org, vbabka@suse.cz, bigeasy@linutronix.de, rostedt@goodmis.org, shakeel.butt@linux.dev, mhocko@suse.com, linux-kernel@vger.kernel.org Subject: [PATCH v3] locking/local_lock, mm: Replace localtry_ helpers with local_trylock_t type Date: Wed, 2 Apr 2025 19:55:14 -0700 Message-Id: <20250403025514.41186-1-alexei.starovoitov@gmail.com> X-Mailer: git-send-email 2.39.5 (Apple Git-154) Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: Alexei Starovoitov Partially revert commit 0aaddfb06882 ("locking/local_lock: Introduce localtry_lock_t"). Remove localtry_*() helpers, since localtry_lock() name might be misinterpreted as "try lock". Introduce local_trylock[_irqsave]() helpers that only work with newly introduced local_trylock_t type. Note that attempt to use local_trylock[_irqsave]() with local_lock_t will cause compilation failure. Usage and behavior in !PREEMPT_RT: local_lock_t lock; // sizeof(lock) == 0 local_lock(&lock); // preempt disable local_lock_irqsave(&lock, ...); // irq save if (local_trylock_irqsave(&lock, ...)) // compilation error local_trylock_t lock; // sizeof(lock) == 4 local_lock(&lock); // preempt disable, acquired = 1 local_lock_irqsave(&lock, ...); // irq save, acquired = 1 if (local_trylock(&lock)) // if (!acquired) preempt disable, acquired = 1 if (local_trylock_irqsave(&lock, ...)) // if (!acquired) irq save, acquired = 1 The existing local_lock_*() macros can be used either with local_lock_t or local_trylock_t. With local_trylock_t they set acquired = 1 while local_unlock_*() clears it. In !PREEMPT_RT local_lock_irqsave(local_lock_t *) disables interrupts to protect critical section, but it doesn't prevent NMI, so the fully reentrant code cannot use local_lock_irqsave(local_lock_t *) for exclusive access. The local_lock_irqsave(local_trylock_t *) helper disables interrupts and sets acquired=1, so local_trylock_irqsave(local_trylock_t *) from NMI attempting to acquire the same lock will return false. In PREEMPT_RT local_lock_irqsave() maps to preemptible spin_lock(). Map local_trylock_irqsave() to preemptible spin_trylock(). When in hard IRQ or NMI return false right away, since spin_trylock() is not safe due to explicit locking in the underneath rt_spin_trylock() implementation. Removing this explicit locking and attempting only "trylock" is undesired due to PI implications. The local_trylock() without _irqsave can be used to avoid the cost of disabling/enabling interrupts by only disabling preemption, so local_trylock() in an interrupt attempting to acquire the same lock will return false. Note there is no need to use local_inc for acquired variable, since it's a percpu variable with strict nesting scopes. Note that guard(local_lock)(&lock) works only for "local_lock_t lock". The patch also makes sure that local_lock_release(l) is called before WRITE_ONCE(l->acquired, 0). Though IRQs are disabled at this point the local_trylock() from NMI will succeed and local_lock_acquire(l) will warn. Acked-by: Vlastimil Babka Acked-by: Sebastian Andrzej Siewior Reviewed-by: Shakeel Butt Fixes: 0aaddfb06882 ("locking/local_lock: Introduce localtry_lock_t") Signed-off-by: Alexei Starovoitov --- include/linux/local_lock.h | 58 ++------ include/linux/local_lock_internal.h | 207 ++++++++++++---------------- mm/memcontrol.c | 39 +++--- 3 files changed, 114 insertions(+), 190 deletions(-) diff --git a/include/linux/local_lock.h b/include/linux/local_lock.h index 1a0bc35839e3..16a2ee4f8310 100644 --- a/include/linux/local_lock.h +++ b/include/linux/local_lock.h @@ -52,44 +52,23 @@ __local_unlock_irqrestore(lock, flags) /** - * localtry_lock_init - Runtime initialize a lock instance - */ -#define localtry_lock_init(lock) __localtry_lock_init(lock) - -/** - * localtry_lock - Acquire a per CPU local lock - * @lock: The lock variable - */ -#define localtry_lock(lock) __localtry_lock(lock) - -/** - * localtry_lock_irq - Acquire a per CPU local lock and disable interrupts - * @lock: The lock variable - */ -#define localtry_lock_irq(lock) __localtry_lock_irq(lock) - -/** - * localtry_lock_irqsave - Acquire a per CPU local lock, save and disable - * interrupts - * @lock: The lock variable - * @flags: Storage for interrupt flags + * local_lock_init - Runtime initialize a lock instance */ -#define localtry_lock_irqsave(lock, flags) \ - __localtry_lock_irqsave(lock, flags) +#define local_trylock_init(lock) __local_trylock_init(lock) /** - * localtry_trylock - Try to acquire a per CPU local lock. + * local_trylock - Try to acquire a per CPU local lock * @lock: The lock variable * * The function can be used in any context such as NMI or HARDIRQ. Due to * locking constrains it will _always_ fail to acquire the lock in NMI or * HARDIRQ context on PREEMPT_RT. */ -#define localtry_trylock(lock) __localtry_trylock(lock) +#define local_trylock(lock) __local_trylock(lock) /** - * localtry_trylock_irqsave - Try to acquire a per CPU local lock, save and disable - * interrupts if acquired + * local_trylock_irqsave - Try to acquire a per CPU local lock, save and disable + * interrupts if acquired * @lock: The lock variable * @flags: Storage for interrupt flags * @@ -97,29 +76,8 @@ * locking constrains it will _always_ fail to acquire the lock in NMI or * HARDIRQ context on PREEMPT_RT. */ -#define localtry_trylock_irqsave(lock, flags) \ - __localtry_trylock_irqsave(lock, flags) - -/** - * local_unlock - Release a per CPU local lock - * @lock: The lock variable - */ -#define localtry_unlock(lock) __localtry_unlock(lock) - -/** - * local_unlock_irq - Release a per CPU local lock and enable interrupts - * @lock: The lock variable - */ -#define localtry_unlock_irq(lock) __localtry_unlock_irq(lock) - -/** - * localtry_unlock_irqrestore - Release a per CPU local lock and restore - * interrupt flags - * @lock: The lock variable - * @flags: Interrupt flags to restore - */ -#define localtry_unlock_irqrestore(lock, flags) \ - __localtry_unlock_irqrestore(lock, flags) +#define local_trylock_irqsave(lock, flags) \ + __local_trylock_irqsave(lock, flags) DEFINE_GUARD(local_lock, local_lock_t __percpu*, local_lock(_T), diff --git a/include/linux/local_lock_internal.h b/include/linux/local_lock_internal.h index 67bd13d142fa..bf2bf40d7b18 100644 --- a/include/linux/local_lock_internal.h +++ b/include/linux/local_lock_internal.h @@ -15,10 +15,11 @@ typedef struct { #endif } local_lock_t; +/* local_trylock() and local_trylock_irqsave() only work with local_trylock_t */ typedef struct { local_lock_t llock; - unsigned int acquired; -} localtry_lock_t; + u8 acquired; +} local_trylock_t; #ifdef CONFIG_DEBUG_LOCK_ALLOC # define LOCAL_LOCK_DEBUG_INIT(lockname) \ @@ -29,6 +30,9 @@ typedef struct { }, \ .owner = NULL, +# define LOCAL_TRYLOCK_DEBUG_INIT(lockname) \ + .llock = { LOCAL_LOCK_DEBUG_INIT((lockname).llock) }, + static inline void local_lock_acquire(local_lock_t *l) { lock_map_acquire(&l->dep_map); @@ -56,6 +60,7 @@ static inline void local_lock_debug_init(local_lock_t *l) } #else /* CONFIG_DEBUG_LOCK_ALLOC */ # define LOCAL_LOCK_DEBUG_INIT(lockname) +# define LOCAL_TRYLOCK_DEBUG_INIT(lockname) static inline void local_lock_acquire(local_lock_t *l) { } static inline void local_trylock_acquire(local_lock_t *l) { } static inline void local_lock_release(local_lock_t *l) { } @@ -63,7 +68,7 @@ static inline void local_lock_debug_init(local_lock_t *l) { } #endif /* !CONFIG_DEBUG_LOCK_ALLOC */ #define INIT_LOCAL_LOCK(lockname) { LOCAL_LOCK_DEBUG_INIT(lockname) } -#define INIT_LOCALTRY_LOCK(lockname) { .llock = { LOCAL_LOCK_DEBUG_INIT(lockname.llock) }} +#define INIT_LOCAL_TRYLOCK(lockname) { LOCAL_TRYLOCK_DEBUG_INIT(lockname) } #define __local_lock_init(lock) \ do { \ @@ -76,6 +81,8 @@ do { \ local_lock_debug_init(lock); \ } while (0) +#define __local_trylock_init(lock) __local_lock_init(lock.llock) + #define __spinlock_nested_bh_init(lock) \ do { \ static struct lock_class_key __key; \ @@ -87,149 +94,117 @@ do { \ local_lock_debug_init(lock); \ } while (0) +#define __local_lock_acquire(lock) \ + do { \ + local_trylock_t *tl; \ + local_lock_t *l; \ + \ + l = (local_lock_t *)this_cpu_ptr(lock); \ + tl = (local_trylock_t *)l; \ + _Generic((lock), \ + local_trylock_t *: ({ \ + lockdep_assert(tl->acquired == 0); \ + WRITE_ONCE(tl->acquired, 1); \ + }), \ + default:(void)0); \ + local_lock_acquire(l); \ + } while (0) + #define __local_lock(lock) \ do { \ preempt_disable(); \ - local_lock_acquire(this_cpu_ptr(lock)); \ + __local_lock_acquire(lock); \ } while (0) #define __local_lock_irq(lock) \ do { \ local_irq_disable(); \ - local_lock_acquire(this_cpu_ptr(lock)); \ + __local_lock_acquire(lock); \ } while (0) #define __local_lock_irqsave(lock, flags) \ do { \ local_irq_save(flags); \ - local_lock_acquire(this_cpu_ptr(lock)); \ - } while (0) - -#define __local_unlock(lock) \ - do { \ - local_lock_release(this_cpu_ptr(lock)); \ - preempt_enable(); \ + __local_lock_acquire(lock); \ } while (0) -#define __local_unlock_irq(lock) \ - do { \ - local_lock_release(this_cpu_ptr(lock)); \ - local_irq_enable(); \ - } while (0) - -#define __local_unlock_irqrestore(lock, flags) \ - do { \ - local_lock_release(this_cpu_ptr(lock)); \ - local_irq_restore(flags); \ - } while (0) - -#define __local_lock_nested_bh(lock) \ - do { \ - lockdep_assert_in_softirq(); \ - local_lock_acquire(this_cpu_ptr(lock)); \ - } while (0) - -#define __local_unlock_nested_bh(lock) \ - local_lock_release(this_cpu_ptr(lock)) - -/* localtry_lock_t variants */ - -#define __localtry_lock_init(lock) \ -do { \ - __local_lock_init(&(lock)->llock); \ - WRITE_ONCE((lock)->acquired, 0); \ -} while (0) - -#define __localtry_lock(lock) \ - do { \ - localtry_lock_t *lt; \ - preempt_disable(); \ - lt = this_cpu_ptr(lock); \ - local_lock_acquire(<->llock); \ - WRITE_ONCE(lt->acquired, 1); \ - } while (0) - -#define __localtry_lock_irq(lock) \ - do { \ - localtry_lock_t *lt; \ - local_irq_disable(); \ - lt = this_cpu_ptr(lock); \ - local_lock_acquire(<->llock); \ - WRITE_ONCE(lt->acquired, 1); \ - } while (0) - -#define __localtry_lock_irqsave(lock, flags) \ - do { \ - localtry_lock_t *lt; \ - local_irq_save(flags); \ - lt = this_cpu_ptr(lock); \ - local_lock_acquire(<->llock); \ - WRITE_ONCE(lt->acquired, 1); \ - } while (0) - -#define __localtry_trylock(lock) \ +#define __local_trylock(lock) \ ({ \ - localtry_lock_t *lt; \ - bool _ret; \ + local_trylock_t *tl; \ \ preempt_disable(); \ - lt = this_cpu_ptr(lock); \ - if (!READ_ONCE(lt->acquired)) { \ - WRITE_ONCE(lt->acquired, 1); \ - local_trylock_acquire(<->llock); \ - _ret = true; \ - } else { \ - _ret = false; \ + tl = this_cpu_ptr(lock); \ + if (READ_ONCE(tl->acquired)) { \ preempt_enable(); \ + tl = NULL; \ + } else { \ + WRITE_ONCE(tl->acquired, 1); \ + local_trylock_acquire( \ + (local_lock_t *)tl); \ } \ - _ret; \ + !!tl; \ }) -#define __localtry_trylock_irqsave(lock, flags) \ +#define __local_trylock_irqsave(lock, flags) \ ({ \ - localtry_lock_t *lt; \ - bool _ret; \ + local_trylock_t *tl; \ \ local_irq_save(flags); \ - lt = this_cpu_ptr(lock); \ - if (!READ_ONCE(lt->acquired)) { \ - WRITE_ONCE(lt->acquired, 1); \ - local_trylock_acquire(<->llock); \ - _ret = true; \ - } else { \ - _ret = false; \ + tl = this_cpu_ptr(lock); \ + if (READ_ONCE(tl->acquired)) { \ local_irq_restore(flags); \ + tl = NULL; \ + } else { \ + WRITE_ONCE(tl->acquired, 1); \ + local_trylock_acquire( \ + (local_lock_t *)tl); \ } \ - _ret; \ + !!tl; \ }) -#define __localtry_unlock(lock) \ +#define __local_lock_release(lock) \ + do { \ + local_trylock_t *tl; \ + local_lock_t *l; \ + \ + l = (local_lock_t *)this_cpu_ptr(lock); \ + tl = (local_trylock_t *)l; \ + local_lock_release(l); \ + _Generic((lock), \ + local_trylock_t *: ({ \ + lockdep_assert(tl->acquired == 1); \ + WRITE_ONCE(tl->acquired, 0); \ + }), \ + default:(void)0); \ + } while (0) + +#define __local_unlock(lock) \ do { \ - localtry_lock_t *lt; \ - lt = this_cpu_ptr(lock); \ - WRITE_ONCE(lt->acquired, 0); \ - local_lock_release(<->llock); \ + __local_lock_release(lock); \ preempt_enable(); \ } while (0) -#define __localtry_unlock_irq(lock) \ +#define __local_unlock_irq(lock) \ do { \ - localtry_lock_t *lt; \ - lt = this_cpu_ptr(lock); \ - WRITE_ONCE(lt->acquired, 0); \ - local_lock_release(<->llock); \ + __local_lock_release(lock); \ local_irq_enable(); \ } while (0) -#define __localtry_unlock_irqrestore(lock, flags) \ +#define __local_unlock_irqrestore(lock, flags) \ do { \ - localtry_lock_t *lt; \ - lt = this_cpu_ptr(lock); \ - WRITE_ONCE(lt->acquired, 0); \ - local_lock_release(<->llock); \ + __local_lock_release(lock); \ local_irq_restore(flags); \ } while (0) +#define __local_lock_nested_bh(lock) \ + do { \ + lockdep_assert_in_softirq(); \ + local_lock_acquire(this_cpu_ptr(lock)); \ + } while (0) + +#define __local_unlock_nested_bh(lock) \ + local_lock_release(this_cpu_ptr(lock)) + #else /* !CONFIG_PREEMPT_RT */ /* @@ -237,16 +212,18 @@ do { \ * critical section while staying preemptible. */ typedef spinlock_t local_lock_t; -typedef spinlock_t localtry_lock_t; +typedef spinlock_t local_trylock_t; #define INIT_LOCAL_LOCK(lockname) __LOCAL_SPIN_LOCK_UNLOCKED((lockname)) -#define INIT_LOCALTRY_LOCK(lockname) INIT_LOCAL_LOCK(lockname) +#define INIT_LOCAL_TRYLOCK(lockname) __LOCAL_SPIN_LOCK_UNLOCKED((lockname)) #define __local_lock_init(l) \ do { \ local_spin_lock_init((l)); \ } while (0) +#define __local_trylock_init(l) __local_lock_init(l) + #define __local_lock(__lock) \ do { \ migrate_disable(); \ @@ -283,17 +260,7 @@ do { \ spin_unlock(this_cpu_ptr((lock))); \ } while (0) -/* localtry_lock_t variants */ - -#define __localtry_lock_init(lock) __local_lock_init(lock) -#define __localtry_lock(lock) __local_lock(lock) -#define __localtry_lock_irq(lock) __local_lock(lock) -#define __localtry_lock_irqsave(lock, flags) __local_lock_irqsave(lock, flags) -#define __localtry_unlock(lock) __local_unlock(lock) -#define __localtry_unlock_irq(lock) __local_unlock(lock) -#define __localtry_unlock_irqrestore(lock, flags) __local_unlock_irqrestore(lock, flags) - -#define __localtry_trylock(lock) \ +#define __local_trylock(lock) \ ({ \ int __locked; \ \ @@ -308,11 +275,11 @@ do { \ __locked; \ }) -#define __localtry_trylock_irqsave(lock, flags) \ +#define __local_trylock_irqsave(lock, flags) \ ({ \ typecheck(unsigned long, flags); \ flags = 0; \ - __localtry_trylock(lock); \ + __local_trylock(lock); \ }) #endif /* CONFIG_PREEMPT_RT */ diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 421740f1bcdc..c96c1f2b9cf5 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -1759,7 +1759,7 @@ void mem_cgroup_print_oom_group(struct mem_cgroup *memcg) } struct memcg_stock_pcp { - localtry_lock_t stock_lock; + local_trylock_t stock_lock; struct mem_cgroup *cached; /* this never be root cgroup */ unsigned int nr_pages; @@ -1774,7 +1774,7 @@ struct memcg_stock_pcp { #define FLUSHING_CACHED_CHARGE 0 }; static DEFINE_PER_CPU(struct memcg_stock_pcp, memcg_stock) = { - .stock_lock = INIT_LOCALTRY_LOCK(stock_lock), + .stock_lock = INIT_LOCAL_TRYLOCK(stock_lock), }; static DEFINE_MUTEX(percpu_charge_mutex); @@ -1805,11 +1805,10 @@ static bool consume_stock(struct mem_cgroup *memcg, unsigned int nr_pages, if (nr_pages > MEMCG_CHARGE_BATCH) return ret; - if (!localtry_trylock_irqsave(&memcg_stock.stock_lock, flags)) { - if (!gfpflags_allow_spinning(gfp_mask)) - return ret; - localtry_lock_irqsave(&memcg_stock.stock_lock, flags); - } + if (gfpflags_allow_spinning(gfp_mask)) + local_lock_irqsave(&memcg_stock.stock_lock, flags); + else if (!local_trylock_irqsave(&memcg_stock.stock_lock, flags)) + return ret; stock = this_cpu_ptr(&memcg_stock); stock_pages = READ_ONCE(stock->nr_pages); @@ -1818,7 +1817,7 @@ static bool consume_stock(struct mem_cgroup *memcg, unsigned int nr_pages, ret = true; } - localtry_unlock_irqrestore(&memcg_stock.stock_lock, flags); + local_unlock_irqrestore(&memcg_stock.stock_lock, flags); return ret; } @@ -1857,14 +1856,14 @@ static void drain_local_stock(struct work_struct *dummy) * drain_stock races is that we always operate on local CPU stock * here with IRQ disabled */ - localtry_lock_irqsave(&memcg_stock.stock_lock, flags); + local_lock_irqsave(&memcg_stock.stock_lock, flags); stock = this_cpu_ptr(&memcg_stock); old = drain_obj_stock(stock); drain_stock(stock); clear_bit(FLUSHING_CACHED_CHARGE, &stock->flags); - localtry_unlock_irqrestore(&memcg_stock.stock_lock, flags); + local_unlock_irqrestore(&memcg_stock.stock_lock, flags); obj_cgroup_put(old); } @@ -1894,7 +1893,7 @@ static void refill_stock(struct mem_cgroup *memcg, unsigned int nr_pages) { unsigned long flags; - if (!localtry_trylock_irqsave(&memcg_stock.stock_lock, flags)) { + if (!local_trylock_irqsave(&memcg_stock.stock_lock, flags)) { /* * In case of unlikely failure to lock percpu stock_lock * uncharge memcg directly. @@ -1907,7 +1906,7 @@ static void refill_stock(struct mem_cgroup *memcg, unsigned int nr_pages) return; } __refill_stock(memcg, nr_pages); - localtry_unlock_irqrestore(&memcg_stock.stock_lock, flags); + local_unlock_irqrestore(&memcg_stock.stock_lock, flags); } /* @@ -1964,9 +1963,9 @@ static int memcg_hotplug_cpu_dead(unsigned int cpu) stock = &per_cpu(memcg_stock, cpu); /* drain_obj_stock requires stock_lock */ - localtry_lock_irqsave(&memcg_stock.stock_lock, flags); + local_lock_irqsave(&memcg_stock.stock_lock, flags); old = drain_obj_stock(stock); - localtry_unlock_irqrestore(&memcg_stock.stock_lock, flags); + local_unlock_irqrestore(&memcg_stock.stock_lock, flags); drain_stock(stock); obj_cgroup_put(old); @@ -2787,7 +2786,7 @@ static void mod_objcg_state(struct obj_cgroup *objcg, struct pglist_data *pgdat, unsigned long flags; int *bytes; - localtry_lock_irqsave(&memcg_stock.stock_lock, flags); + local_lock_irqsave(&memcg_stock.stock_lock, flags); stock = this_cpu_ptr(&memcg_stock); /* @@ -2836,7 +2835,7 @@ static void mod_objcg_state(struct obj_cgroup *objcg, struct pglist_data *pgdat, if (nr) __mod_objcg_mlstate(objcg, pgdat, idx, nr); - localtry_unlock_irqrestore(&memcg_stock.stock_lock, flags); + local_unlock_irqrestore(&memcg_stock.stock_lock, flags); obj_cgroup_put(old); } @@ -2846,7 +2845,7 @@ static bool consume_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes) unsigned long flags; bool ret = false; - localtry_lock_irqsave(&memcg_stock.stock_lock, flags); + local_lock_irqsave(&memcg_stock.stock_lock, flags); stock = this_cpu_ptr(&memcg_stock); if (objcg == READ_ONCE(stock->cached_objcg) && stock->nr_bytes >= nr_bytes) { @@ -2854,7 +2853,7 @@ static bool consume_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes) ret = true; } - localtry_unlock_irqrestore(&memcg_stock.stock_lock, flags); + local_unlock_irqrestore(&memcg_stock.stock_lock, flags); return ret; } @@ -2946,7 +2945,7 @@ static void refill_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes, unsigned long flags; unsigned int nr_pages = 0; - localtry_lock_irqsave(&memcg_stock.stock_lock, flags); + local_lock_irqsave(&memcg_stock.stock_lock, flags); stock = this_cpu_ptr(&memcg_stock); if (READ_ONCE(stock->cached_objcg) != objcg) { /* reset if necessary */ @@ -2960,7 +2959,7 @@ static void refill_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes, stock->nr_bytes &= (PAGE_SIZE - 1); } - localtry_unlock_irqrestore(&memcg_stock.stock_lock, flags); + local_unlock_irqrestore(&memcg_stock.stock_lock, flags); obj_cgroup_put(old); if (nr_pages)