Commit 3cf3fabc authored Oct 30, 2023 by Linus Torvalds

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()
  ...

parents 9cda4eb0 c73801ae

arch/alpha/include/asm/local.h

+16 −17

Original line number	Diff line number	Diff line
		@@ -65,28 +65,27 @@ static __inline__ bool local_try_cmpxchg(local_t l, long old, long new)
		#define local_xchg(l, n) (xchg_local(&((l)->a.counter), (n)))

		/**
		* local_add_unless - add unless the number is a given value
		* local_add_unless - add unless the number is already a given value
		* @l: pointer of type local_t
		* @a: the amount to add to l...
		* @u: ...unless l is equal to u.
		*
		* Atomically adds @a to @l, so long as it was not @u.
		* Returns non-zero if @l was not @u, and zero otherwise.
		* Atomically adds @a to @l, if @v was not already @u.
		* Returns true if the addition was done.
		*/
		#define local_add_unless(l, a, u) \
		({ \
		long c, old; \
		c = local_read(l); \
		for (;;) { \
		if (unlikely(c == (u))) \
		break; \
		old = local_cmpxchg((l), c, c + (a)); \
		if (likely(old == c)) \
		break; \
		c = old; \
		} \
		c != (u); \
		})
		static __inline__ bool
		local_add_unless(local_t *l, long a, long u)
		{
		long c = local_read(l);

		do {
		if (unlikely(c == u))
		return false;
		} while (!local_try_cmpxchg(l, &c, c + a));

		return true;
		}

		#define local_inc_not_zero(l) local_add_unless((l), 1, 0)

		#define local_add_negative(a, l) (local_add_return((a), (l)) < 0)

arch/alpha/kernel/syscalls/syscall.tbl

+4 −0

Original line number	Diff line number	Diff line
		@@ -492,3 +492,7 @@
		560 common set_mempolicy_home_node sys_ni_syscall
		561 common cachestat sys_cachestat
		562 common fchmodat2 sys_fchmodat2
		# 563 reserved for map_shadow_stack
		564 common futex_wake sys_futex_wake
		565 common futex_wait sys_futex_wait
		566 common futex_requeue sys_futex_requeue

arch/arm/tools/syscall.tbl

+3 −0

Original line number	Diff line number	Diff line
		@@ -466,3 +466,6 @@
		450 common set_mempolicy_home_node sys_set_mempolicy_home_node
		451 common cachestat sys_cachestat
		452 common fchmodat2 sys_fchmodat2
		454 common futex_wake sys_futex_wake
		455 common futex_wait sys_futex_wait
		456 common futex_requeue sys_futex_requeue

arch/arm64/include/asm/unistd.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -39,7 +39,7 @@
		#define __ARM_NR_compat_set_tls (__ARM_NR_COMPAT_BASE + 5)
		#define __ARM_NR_COMPAT_END (__ARM_NR_COMPAT_BASE + 0x800)

		#define __NR_compat_syscalls 453
		#define __NR_compat_syscalls 457
		#endif

		#define __ARCH_WANT_SYS_CLONE

arch/arm64/include/asm/unistd32.h

+6 −0

Original line number	Diff line number	Diff line
		@@ -911,6 +911,12 @@ __SYSCALL(__NR_set_mempolicy_home_node, sys_set_mempolicy_home_node)
		__SYSCALL(__NR_cachestat, sys_cachestat)
		#define __NR_fchmodat2 452
		__SYSCALL(__NR_fchmodat2, sys_fchmodat2)
		#define __NR_futex_wake 454
		__SYSCALL(__NR_futex_wake, sys_futex_wake)
		#define __NR_futex_wait 455
		__SYSCALL(__NR_futex_wait, sys_futex_wait)
		#define __NR_futex_requeue 456
		__SYSCALL(__NR_futex_requeue, sys_futex_requeue)

		/*
		* Please add new compat syscalls above this comment and update