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author | Linus Torvalds <torvalds@linux-foundation.org> | 2023-10-31 01:38:48 +0300 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2023-10-31 01:38:48 +0300 |
commit | 3cf3fabccb9dc821ffaec3ad6bf0cd6b278bd012 (patch) | |
tree | 76bf15f5939812608b8ea514c3c50fd1ac8acebb /kernel/locking | |
parent | 9cda4eb04a68aee4d795438917a4e958b2b2aa07 (diff) | |
parent | c73801ae4f22b390228ebf471d55668e824198b6 (diff) | |
download | linux-3cf3fabccb9dc821ffaec3ad6bf0cd6b278bd012.tar.xz |
Merge tag 'locking-core-2023-10-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking updates from Info Molnar:
"Futex improvements:
- Add the 'futex2' syscall ABI, which is an attempt to get away from
the multiplex syscall and adds a little room for extentions, while
lifting some limitations.
- Fix futex PI recursive rt_mutex waiter state bug
- Fix inter-process shared futexes on no-MMU systems
- Use folios instead of pages
Micro-optimizations of locking primitives:
- Improve arch_spin_value_unlocked() on asm-generic ticket spinlock
architectures, to improve lockref code generation
- Improve the x86-32 lockref_get_not_zero() main loop by adding
build-time CMPXCHG8B support detection for the relevant lockref
code, and by better interfacing the CMPXCHG8B assembly code with
the compiler
- Introduce arch_sync_try_cmpxchg() on x86 to improve
sync_try_cmpxchg() code generation. Convert some sync_cmpxchg()
users to sync_try_cmpxchg().
- Micro-optimize rcuref_put_slowpath()
Locking debuggability improvements:
- Improve CONFIG_DEBUG_RT_MUTEXES=y to have a fast-path as well
- Enforce atomicity of sched_submit_work(), which is de-facto atomic
but was un-enforced previously.
- Extend <linux/cleanup.h>'s no_free_ptr() with __must_check
semantics
- Fix ww_mutex self-tests
- Clean up const-propagation in <linux/seqlock.h> and simplify the
API-instantiation macros a bit
RT locking improvements:
- Provide the rt_mutex_*_schedule() primitives/helpers and use them
in the rtmutex code to avoid recursion vs. rtlock on the PI state.
- Add nested blocking lockdep asserts to rt_mutex_lock(),
rtlock_lock() and rwbase_read_lock()
.. plus misc fixes & cleanups"
* tag 'locking-core-2023-10-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (39 commits)
futex: Don't include process MM in futex key on no-MMU
locking/seqlock: Fix grammar in comment
alpha: Fix up new futex syscall numbers
locking/seqlock: Propagate 'const' pointers within read-only methods, remove forced type casts
locking/lockdep: Fix string sizing bug that triggers a format-truncation compiler-warning
locking/seqlock: Change __seqprop() to return the function pointer
locking/seqlock: Simplify SEQCOUNT_LOCKNAME()
locking/atomics: Use atomic_try_cmpxchg_release() to micro-optimize rcuref_put_slowpath()
locking/atomic, xen: Use sync_try_cmpxchg() instead of sync_cmpxchg()
locking/atomic/x86: Introduce arch_sync_try_cmpxchg()
locking/atomic: Add generic support for sync_try_cmpxchg() and its fallback
locking/seqlock: Fix typo in comment
futex/requeue: Remove unnecessary ‘NULL’ initialization from futex_proxy_trylock_atomic()
locking/local, arch: Rewrite local_add_unless() as a static inline function
locking/debug: Fix debugfs API return value checks to use IS_ERR()
locking/ww_mutex/test: Make sure we bail out instead of livelock
locking/ww_mutex/test: Fix potential workqueue corruption
locking/ww_mutex/test: Use prng instead of rng to avoid hangs at bootup
futex: Add sys_futex_requeue()
futex: Add flags2 argument to futex_requeue()
...
Diffstat (limited to 'kernel/locking')
-rw-r--r-- | kernel/locking/lock_events.c | 10 | ||||
-rw-r--r-- | kernel/locking/lockdep_proc.c | 2 | ||||
-rw-r--r-- | kernel/locking/rtmutex.c | 37 | ||||
-rw-r--r-- | kernel/locking/rwbase_rt.c | 8 | ||||
-rw-r--r-- | kernel/locking/rwsem.c | 8 | ||||
-rw-r--r-- | kernel/locking/spinlock_rt.c | 6 | ||||
-rw-r--r-- | kernel/locking/test-ww_mutex.c | 48 | ||||
-rw-r--r-- | kernel/locking/ww_rt_mutex.c | 2 |
8 files changed, 96 insertions, 25 deletions
diff --git a/kernel/locking/lock_events.c b/kernel/locking/lock_events.c index fa2c2f951c6b..e68d82099558 100644 --- a/kernel/locking/lock_events.c +++ b/kernel/locking/lock_events.c @@ -146,7 +146,7 @@ static int __init init_lockevent_counts(void) struct dentry *d_counts = debugfs_create_dir(LOCK_EVENTS_DIR, NULL); int i; - if (!d_counts) + if (IS_ERR(d_counts)) goto out; /* @@ -159,14 +159,14 @@ static int __init init_lockevent_counts(void) for (i = 0; i < lockevent_num; i++) { if (skip_lockevent(lockevent_names[i])) continue; - if (!debugfs_create_file(lockevent_names[i], 0400, d_counts, - (void *)(long)i, &fops_lockevent)) + if (IS_ERR(debugfs_create_file(lockevent_names[i], 0400, d_counts, + (void *)(long)i, &fops_lockevent))) goto fail_undo; } - if (!debugfs_create_file(lockevent_names[LOCKEVENT_reset_cnts], 0200, + if (IS_ERR(debugfs_create_file(lockevent_names[LOCKEVENT_reset_cnts], 0200, d_counts, (void *)(long)LOCKEVENT_reset_cnts, - &fops_lockevent)) + &fops_lockevent))) goto fail_undo; return 0; diff --git a/kernel/locking/lockdep_proc.c b/kernel/locking/lockdep_proc.c index 15fdc7fa5c68..e2bfb1db589d 100644 --- a/kernel/locking/lockdep_proc.c +++ b/kernel/locking/lockdep_proc.c @@ -440,7 +440,7 @@ static void snprint_time(char *buf, size_t bufsiz, s64 nr) static void seq_time(struct seq_file *m, s64 time) { - char num[15]; + char num[22]; snprint_time(num, sizeof(num), time); seq_printf(m, " %14s", num); diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c index 21db0df0eb00..4a10e8c16fd2 100644 --- a/kernel/locking/rtmutex.c +++ b/kernel/locking/rtmutex.c @@ -218,6 +218,11 @@ static __always_inline bool rt_mutex_cmpxchg_acquire(struct rt_mutex_base *lock, return try_cmpxchg_acquire(&lock->owner, &old, new); } +static __always_inline bool rt_mutex_try_acquire(struct rt_mutex_base *lock) +{ + return rt_mutex_cmpxchg_acquire(lock, NULL, current); +} + static __always_inline bool rt_mutex_cmpxchg_release(struct rt_mutex_base *lock, struct task_struct *old, struct task_struct *new) @@ -297,6 +302,20 @@ static __always_inline bool rt_mutex_cmpxchg_acquire(struct rt_mutex_base *lock, } +static int __sched rt_mutex_slowtrylock(struct rt_mutex_base *lock); + +static __always_inline bool rt_mutex_try_acquire(struct rt_mutex_base *lock) +{ + /* + * With debug enabled rt_mutex_cmpxchg trylock() will always fail. + * + * Avoid unconditionally taking the slow path by using + * rt_mutex_slow_trylock() which is covered by the debug code and can + * acquire a non-contended rtmutex. + */ + return rt_mutex_slowtrylock(lock); +} + static __always_inline bool rt_mutex_cmpxchg_release(struct rt_mutex_base *lock, struct task_struct *old, struct task_struct *new) @@ -1613,7 +1632,7 @@ static int __sched rt_mutex_slowlock_block(struct rt_mutex_base *lock, raw_spin_unlock_irq(&lock->wait_lock); if (!owner || !rtmutex_spin_on_owner(lock, waiter, owner)) - schedule(); + rt_mutex_schedule(); raw_spin_lock_irq(&lock->wait_lock); set_current_state(state); @@ -1642,7 +1661,7 @@ static void __sched rt_mutex_handle_deadlock(int res, int detect_deadlock, WARN(1, "rtmutex deadlock detected\n"); while (1) { set_current_state(TASK_INTERRUPTIBLE); - schedule(); + rt_mutex_schedule(); } } @@ -1738,6 +1757,15 @@ static int __sched rt_mutex_slowlock(struct rt_mutex_base *lock, int ret; /* + * Do all pre-schedule work here, before we queue a waiter and invoke + * PI -- any such work that trips on rtlock (PREEMPT_RT spinlock) would + * otherwise recurse back into task_blocks_on_rt_mutex() through + * rtlock_slowlock() and will then enqueue a second waiter for this + * same task and things get really confusing real fast. + */ + rt_mutex_pre_schedule(); + + /* * Technically we could use raw_spin_[un]lock_irq() here, but this can * be called in early boot if the cmpxchg() fast path is disabled * (debug, no architecture support). In this case we will acquire the @@ -1748,6 +1776,7 @@ static int __sched rt_mutex_slowlock(struct rt_mutex_base *lock, raw_spin_lock_irqsave(&lock->wait_lock, flags); ret = __rt_mutex_slowlock_locked(lock, ww_ctx, state); raw_spin_unlock_irqrestore(&lock->wait_lock, flags); + rt_mutex_post_schedule(); return ret; } @@ -1755,7 +1784,9 @@ static int __sched rt_mutex_slowlock(struct rt_mutex_base *lock, static __always_inline int __rt_mutex_lock(struct rt_mutex_base *lock, unsigned int state) { - if (likely(rt_mutex_cmpxchg_acquire(lock, NULL, current))) + lockdep_assert(!current->pi_blocked_on); + + if (likely(rt_mutex_try_acquire(lock))) return 0; return rt_mutex_slowlock(lock, NULL, state); diff --git a/kernel/locking/rwbase_rt.c b/kernel/locking/rwbase_rt.c index 25ec0239477c..34a59569db6b 100644 --- a/kernel/locking/rwbase_rt.c +++ b/kernel/locking/rwbase_rt.c @@ -71,6 +71,7 @@ static int __sched __rwbase_read_lock(struct rwbase_rt *rwb, struct rt_mutex_base *rtm = &rwb->rtmutex; int ret; + rwbase_pre_schedule(); raw_spin_lock_irq(&rtm->wait_lock); /* @@ -125,12 +126,15 @@ static int __sched __rwbase_read_lock(struct rwbase_rt *rwb, rwbase_rtmutex_unlock(rtm); trace_contention_end(rwb, ret); + rwbase_post_schedule(); return ret; } static __always_inline int rwbase_read_lock(struct rwbase_rt *rwb, unsigned int state) { + lockdep_assert(!current->pi_blocked_on); + if (rwbase_read_trylock(rwb)) return 0; @@ -237,6 +241,8 @@ static int __sched rwbase_write_lock(struct rwbase_rt *rwb, /* Force readers into slow path */ atomic_sub(READER_BIAS, &rwb->readers); + rwbase_pre_schedule(); + raw_spin_lock_irqsave(&rtm->wait_lock, flags); if (__rwbase_write_trylock(rwb)) goto out_unlock; @@ -248,6 +254,7 @@ static int __sched rwbase_write_lock(struct rwbase_rt *rwb, if (rwbase_signal_pending_state(state, current)) { rwbase_restore_current_state(); __rwbase_write_unlock(rwb, 0, flags); + rwbase_post_schedule(); trace_contention_end(rwb, -EINTR); return -EINTR; } @@ -266,6 +273,7 @@ static int __sched rwbase_write_lock(struct rwbase_rt *rwb, out_unlock: raw_spin_unlock_irqrestore(&rtm->wait_lock, flags); + rwbase_post_schedule(); return 0; } diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c index 9eabd585ce7a..2340b6d90ec6 100644 --- a/kernel/locking/rwsem.c +++ b/kernel/locking/rwsem.c @@ -1427,8 +1427,14 @@ static inline void __downgrade_write(struct rw_semaphore *sem) #define rwbase_signal_pending_state(state, current) \ signal_pending_state(state, current) +#define rwbase_pre_schedule() \ + rt_mutex_pre_schedule() + #define rwbase_schedule() \ - schedule() + rt_mutex_schedule() + +#define rwbase_post_schedule() \ + rt_mutex_post_schedule() #include "rwbase_rt.c" diff --git a/kernel/locking/spinlock_rt.c b/kernel/locking/spinlock_rt.c index 48a19ed8486d..38e292454fcc 100644 --- a/kernel/locking/spinlock_rt.c +++ b/kernel/locking/spinlock_rt.c @@ -37,6 +37,8 @@ static __always_inline void rtlock_lock(struct rt_mutex_base *rtm) { + lockdep_assert(!current->pi_blocked_on); + if (unlikely(!rt_mutex_cmpxchg_acquire(rtm, NULL, current))) rtlock_slowlock(rtm); } @@ -184,9 +186,13 @@ static __always_inline int rwbase_rtmutex_trylock(struct rt_mutex_base *rtm) #define rwbase_signal_pending_state(state, current) (0) +#define rwbase_pre_schedule() + #define rwbase_schedule() \ schedule_rtlock() +#define rwbase_post_schedule() + #include "rwbase_rt.c" /* * The common functions which get wrapped into the rwlock API. diff --git a/kernel/locking/test-ww_mutex.c b/kernel/locking/test-ww_mutex.c index 93cca6e69860..78719e1ef1b1 100644 --- a/kernel/locking/test-ww_mutex.c +++ b/kernel/locking/test-ww_mutex.c @@ -9,7 +9,7 @@ #include <linux/delay.h> #include <linux/kthread.h> #include <linux/module.h> -#include <linux/random.h> +#include <linux/prandom.h> #include <linux/slab.h> #include <linux/ww_mutex.h> @@ -386,6 +386,19 @@ struct stress { int nlocks; }; +struct rnd_state rng; +DEFINE_SPINLOCK(rng_lock); + +static inline u32 prandom_u32_below(u32 ceil) +{ + u32 ret; + + spin_lock(&rng_lock); + ret = prandom_u32_state(&rng) % ceil; + spin_unlock(&rng_lock); + return ret; +} + static int *get_random_order(int count) { int *order; @@ -399,7 +412,7 @@ static int *get_random_order(int count) order[n] = n; for (n = count - 1; n > 1; n--) { - r = get_random_u32_below(n + 1); + r = prandom_u32_below(n + 1); if (r != n) { tmp = order[n]; order[n] = order[r]; @@ -452,21 +465,21 @@ retry: ww_mutex_unlock(&locks[order[n]]); if (err == -EDEADLK) { - ww_mutex_lock_slow(&locks[order[contended]], &ctx); - goto retry; + if (!time_after(jiffies, stress->timeout)) { + ww_mutex_lock_slow(&locks[order[contended]], &ctx); + goto retry; + } } + ww_acquire_fini(&ctx); if (err) { pr_err_once("stress (%s) failed with %d\n", __func__, err); break; } - - ww_acquire_fini(&ctx); } while (!time_after(jiffies, stress->timeout)); kfree(order); - kfree(stress); } struct reorder_lock { @@ -531,7 +544,6 @@ out: list_for_each_entry_safe(ll, ln, &locks, link) kfree(ll); kfree(order); - kfree(stress); } static void stress_one_work(struct work_struct *work) @@ -552,8 +564,6 @@ static void stress_one_work(struct work_struct *work) break; } } while (!time_after(jiffies, stress->timeout)); - - kfree(stress); } #define STRESS_INORDER BIT(0) @@ -564,15 +574,24 @@ static void stress_one_work(struct work_struct *work) static int stress(int nlocks, int nthreads, unsigned int flags) { struct ww_mutex *locks; - int n; + struct stress *stress_array; + int n, count; locks = kmalloc_array(nlocks, sizeof(*locks), GFP_KERNEL); if (!locks) return -ENOMEM; + stress_array = kmalloc_array(nthreads, sizeof(*stress_array), + GFP_KERNEL); + if (!stress_array) { + kfree(locks); + return -ENOMEM; + } + for (n = 0; n < nlocks; n++) ww_mutex_init(&locks[n], &ww_class); + count = 0; for (n = 0; nthreads; n++) { struct stress *stress; void (*fn)(struct work_struct *work); @@ -596,9 +615,7 @@ static int stress(int nlocks, int nthreads, unsigned int flags) if (!fn) continue; - stress = kmalloc(sizeof(*stress), GFP_KERNEL); - if (!stress) - break; + stress = &stress_array[count++]; INIT_WORK(&stress->work, fn); stress->locks = locks; @@ -613,6 +630,7 @@ static int stress(int nlocks, int nthreads, unsigned int flags) for (n = 0; n < nlocks; n++) ww_mutex_destroy(&locks[n]); + kfree(stress_array); kfree(locks); return 0; @@ -625,6 +643,8 @@ static int __init test_ww_mutex_init(void) printk(KERN_INFO "Beginning ww mutex selftests\n"); + prandom_seed_state(&rng, get_random_u64()); + wq = alloc_workqueue("test-ww_mutex", WQ_UNBOUND, 0); if (!wq) return -ENOMEM; diff --git a/kernel/locking/ww_rt_mutex.c b/kernel/locking/ww_rt_mutex.c index d1473c624105..c7196de838ed 100644 --- a/kernel/locking/ww_rt_mutex.c +++ b/kernel/locking/ww_rt_mutex.c @@ -62,7 +62,7 @@ __ww_rt_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ww_ctx, } mutex_acquire_nest(&rtm->dep_map, 0, 0, nest_lock, ip); - if (likely(rt_mutex_cmpxchg_acquire(&rtm->rtmutex, NULL, current))) { + if (likely(rt_mutex_try_acquire(&rtm->rtmutex))) { if (ww_ctx) ww_mutex_set_context_fastpath(lock, ww_ctx); return 0; |