linux.git/kernel/locking/spinlock.c, branch v6.6.131

locking/spinlocks: Mark spinlocks noinline when inline spinlocks are disabled

2022-08-04T09:05:43+00:00

Otherwise LTO will inline them anyways and cause a large kernel text increase.

Since the explicit intention here is to not inline them marking them noinline
is good documentation even for the non-LTO case.

Signed-off-by: Andi Kleen 
Signed-off-by: Martin Liska 
Signed-off-by: Jiri Slaby 
Signed-off-by: Ingo Molnar 
Link: https://lore.kernel.org/r/20220719110548.1544-1-jslaby@suse.cz

locking/rwlocks: introduce write_lock_nested

2022-01-22T06:33:37+00:00

In preparation for converting bit_spin_lock to rwlock in zsmalloc so
that multiple writers of zspages can run at the same time but those
zspages are supposed to be different zspage instance.  Thus, it's not
deadlock.  This patch adds write_lock_nested to support the case for
LOCKDEP.

[minchan@kernel.org: fix write_lock_nested for RT]
  Link: https://lkml.kernel.org/r/YZfrMTAXV56HFWJY@google.com
[bigeasy@linutronix.de: fixup write_lock_nested() implementation]
  Link: https://lkml.kernel.org/r/20211123170134.y6xb7pmpgdn4m3bn@linutronix.de

Link: https://lkml.kernel.org/r/20211115185909.3949505-8-minchan@kernel.org
Signed-off-by: Minchan Kim 
Signed-off-by: Sebastian Andrzej Siewior 
Acked-by: Peter Zijlstra (Intel) 
Acked-by: Sebastian Andrzej Siewior 
Tested-by: Sebastian Andrzej Siewior 
Cc: Mike Galbraith 
Cc: Sergey Senozhatsky 
Cc: Thomas Gleixner 
Cc: Naresh Kamboju 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

locking: Remove spin_lock_flags() etc

2021-10-30T14:37:28+00:00

parisc, ia64 and powerpc32 are the only remaining architectures that
provide custom arch_{spin,read,write}_lock_flags() functions, which are
meant to re-enable interrupts while waiting for a spinlock.

However, none of these can actually run into this codepath, because
it is only called on architectures without CONFIG_GENERIC_LOCKBREAK,
or when CONFIG_DEBUG_LOCK_ALLOC is set without CONFIG_LOCKDEP, and none
of those combinations are possible on the three architectures.

Going back in the git history, it appears that arch/mn10300 may have
been able to run into this code path, but there is a good chance that
it never worked. On the architectures that still exist, it was
already impossible to hit back in 2008 after the introduction of
CONFIG_GENERIC_LOCKBREAK, and possibly earlier.

As this is all dead code, just remove it and the helper functions built
around it. For arch/ia64, the inline asm could be cleaned up, but
it seems safer to leave it untouched.

Signed-off-by: Arnd Bergmann 
Signed-off-by: Peter Zijlstra (Intel) 
Acked-by: Helge Deller   # parisc
Link: https://lore.kernel.org/r/20211022120058.1031690-1-arnd@kernel.org

locking/rwlock: Provide RT variant

2021-08-17T15:50:51+00:00

Similar to rw_semaphores, on RT the rwlock substitution is not writer fair,
because it's not feasible to have a writer inherit its priority to
multiple readers. Readers blocked on a writer follow the normal rules of
priority inheritance. Like RT spinlocks, RT rwlocks are state preserving
across the slow lock operations (contended case).

Signed-off-by: Thomas Gleixner 
Signed-off-by: Peter Zijlstra (Intel) 
Signed-off-by: Ingo Molnar 
Link: https://lore.kernel.org/r/20210815211303.882793524@linutronix.de

locking: Fix typos in comments

2021-03-22T01:45:52+00:00

Fix ~16 single-word typos in locking code comments.

Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: Paul E. McKenney 
Cc: Will Deacon 
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar

asm-generic/mmiowb: Add generic implementation of mmiowb() tracking

2019-04-08T10:59:39+00:00

In preparation for removing all explicit mmiowb() calls from driver
code, implement a tracking system in asm-generic based loosely on the
PowerPC implementation. This allows architectures with a non-empty
mmiowb() definition to have the barrier automatically inserted in
spin_unlock() following a critical section containing an I/O write.

Acked-by: Linus Torvalds 
Signed-off-by: Will Deacon

locking/core: Remove break_lock field when CONFIG_GENERIC_LOCKBREAK=y

2017-12-12T10:24:01+00:00

When CONFIG_GENERIC_LOCKBEAK=y, locking structures grow an extra int ->break_lock
field which is used to implement raw_spin_is_contended() by setting the field
to 1 when waiting on a lock and clearing it to zero when holding a lock.
However, there are a few problems with this approach:

  - There is a write-write race between a CPU successfully taking the lock
    (and subsequently writing break_lock = 0) and a waiter waiting on
    the lock (and subsequently writing break_lock = 1). This could result
    in a contended lock being reported as uncontended and vice-versa.

  - On machines with store buffers, nothing guarantees that the writes
    to break_lock are visible to other CPUs at any particular time.

  - READ_ONCE/WRITE_ONCE are not used, so the field is potentially
    susceptible to harmful compiler optimisations,

Consequently, the usefulness of this field is unclear and we'd be better off
removing it and allowing architectures to implement raw_spin_is_contended() by
providing a definition of arch_spin_is_contended(), as they can when
CONFIG_GENERIC_LOCKBREAK=n.

Signed-off-by: Will Deacon 
Acked-by: Peter Zijlstra 
Cc: Heiko Carstens 
Cc: Linus Torvalds 
Cc: Martin Schwidefsky 
Cc: Sebastian Ott 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/1511894539-7988-3-git-send-email-will.deacon@arm.com
Signed-off-by: Ingo Molnar

locking/core: Fix deadlock during boot on systems with GENERIC_LOCKBREAK

2017-12-12T10:24:01+00:00

Commit:

  a8a217c22116 ("locking/core: Remove {read,spin,write}_can_lock()")

removed the definition of raw_spin_can_lock(), causing the GENERIC_LOCKBREAK
spin_lock() routines to poll the ->break_lock field when waiting on a lock.

This has been reported to cause a deadlock during boot on s390, because
the ->break_lock field is also set by the waiters, and can potentially
remain set indefinitely if no other CPUs come in to take the lock after
it has been released.

This patch removes the explicit spinning on ->break_lock from the waiters,
instead relying on the outer trylock() operation to determine when the
lock is available.

Reported-by: Sebastian Ott 
Tested-by: Sebastian Ott 
Signed-off-by: Will Deacon 
Acked-by: Peter Zijlstra 
Cc: Heiko Carstens 
Cc: Linus Torvalds 
Cc: Martin Schwidefsky 
Cc: Thomas Gleixner 
Fixes: a8a217c22116 ("locking/core: Remove {read,spin,write}_can_lock()")
Link: http://lkml.kernel.org/r/1511894539-7988-2-git-send-email-will.deacon@arm.com
Signed-off-by: Ingo Molnar

locking/rwlocks: Fix comments

2017-11-07T11:22:21+00:00

- fix the list of locking API headers in kernel/locking/spinlock.c
- fix an #endif comment

Signed-off-by: Cheng Jian 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: huawei.libin@huawei.com
Cc: xiexiuqi@huawei.com
Link: http://lkml.kernel.org/r/1509706788-152547-1-git-send-email-cj.chengjian@huawei.com
Signed-off-by: Ingo Molnar

Merge branch 'linus' into locking/core, to resolve conflicts

2017-11-07T09:32:44+00:00

Conflicts:
	include/linux/compiler-clang.h
	include/linux/compiler-gcc.h
	include/linux/compiler-intel.h
	include/uapi/linux/stddef.h

Signed-off-by: Ingo Molnar