user/sven/linux.git/include/linux/spinlock.h, branch v5.4.249

locking/spinlocks: Use CONFIG_PREEMPTION

2019-07-31T17:03:35Z

CONFIG_PREEMPTION is selected by CONFIG_PREEMPT and by CONFIG_PREEMPT_RT. Both PREEMPT and PREEMPT_RT require the same functionality which today depends on CONFIG_PREEMPT. Adjust the comments in the locking code. Signed-off-by: Thomas Gleixner Acked-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Masami Hiramatsu Cc: Paolo Bonzini Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Steven Rostedt Link: http://lkml.kernel.org/r/20190726212124.302995288@linutronix.de Signed-off-by: Ingo Molnar

mmiowb: Hook up mmiowb helpers to spinlocks and generic I/O accessors

2019-04-08T10:59:47Z

Removing explicit calls to mmiowb() from driver code means that we must now call into the generic mmiowb_spin_{lock,unlock}() functions from the core spinlock code. In order to elide barriers following critical sections without any I/O writes, we also hook into the asm-generic I/O routines. Acked-by: Linus Torvalds Signed-off-by: Will Deacon

ila: make lockdep happy again

2018-08-16T19:14:42Z

Previously, alloc_ila_locks() and bucket_table_alloc() call spin_lock_init() separately, therefore they have two different lock names and lock class keys. However, after commit b893281715ab ("ila: Call library function alloc_bucket_locks") they both call helper alloc_bucket_spinlocks() which now only has one lock name and lock class key. This causes a few bogus lockdep warnings as reported by syzbot. Fix this by making alloc_bucket_locks() a macro and pass declaration name as lock name and a static lock class key inside the macro. Fixes: b893281715ab ("ila: Call library function alloc_bucket_locks") Reported-by: Cc: Tom Herbert Signed-off-by: Cong Wang Signed-off-by: David S. Miller

locking/spinlock, sched/core: Clarify requirements for smp_mb__after_spinlock()

2018-07-17T07:30:33Z

There are 11 interpretations of the requirements described in the header comment for smp_mb__after_spinlock(): one for each LKMM maintainer, and one currently encoded in the Cat file. Stick to the latter (until a more satisfactory solution is available). This also reworks some snippets related to the barrier to illustrate the requirements and to link them to the idioms which are relied upon at its call sites. Suggested-by: Boqun Feng Signed-off-by: Andrea Parri Signed-off-by: Paul E. McKenney Acked-by: Peter Zijlstra Cc: Linus Torvalds Cc: Thomas Gleixner Cc: Will Deacon Cc: akiyks@gmail.com Cc: dhowells@redhat.com Cc: j.alglave@ucl.ac.uk Cc: linux-arch@vger.kernel.org Cc: luc.maranget@inria.fr Cc: npiggin@gmail.com Cc: parri.andrea@gmail.com Cc: stern@rowland.harvard.edu Link: http://lkml.kernel.org/r/20180716180605.16115-11-paulmck@linux.vnet.ibm.com Signed-off-by: Ingo Molnar

atomic: Add irqsave variant of atomic_dec_and_lock()

2018-06-12T21:33:24Z

There are in-tree users of atomic_dec_and_lock() which must acquire the spin lock with interrupts disabled. To workaround the lack of an irqsave variant of atomic_dec_and_lock() they use local_irq_save() at the call site. This causes extra code and creates in some places unneeded long interrupt disabled times. These places need also extra treatment for PREEMPT_RT due to the disconnect of the irq disabling and the lock function. Implement the missing irqsave variant of the function. Signed-off-by: Anna-Maria Gleixner Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Thomas Gleixner Acked-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r20180612161621.22645-3-bigeasy@linutronix.de

locking/spinlocks: Document the semantics of spin_is_locked()

2018-05-15T06:11:15Z

There appeared to be a certain, recurrent uncertainty concerning the semantics of spin_is_locked(), likely a consequence of the fact that this semantics remains undocumented or that it has been historically linked to the (likewise unclear) semantics of spin_unlock_wait(). A recent auditing [1] of the callers of the primitive confirmed that none of them are relying on particular ordering guarantees; document this semantics by adding a docbook header to spin_is_locked(). Also, describe behaviors specific to certain CONFIG_SMP=n builds. [1] https://marc.info/?l=linux-kernel&m=151981440005264&w=2 https://marc.info/?l=linux-kernel&m=152042843808540&w=2 https://marc.info/?l=linux-kernel&m=152043346110262&w=2 Co-Developed-by: Andrea Parri Co-Developed-by: Alan Stern Co-Developed-by: David Howells Signed-off-by: Andrea Parri Signed-off-by: Alan Stern Signed-off-by: David Howells Signed-off-by: Paul E. McKenney Acked-by: Randy Dunlap Cc: Akira Yokosawa Cc: Andrew Morton Cc: Boqun Feng Cc: Jade Alglave Cc: Linus Torvalds Cc: Luc Maranget Cc: Nicholas Piggin Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Will Deacon Cc: linux-arch@vger.kernel.org Cc: parri.andrea@gmail.com Link: http://lkml.kernel.org/r/1526338889-7003-1-git-send-email-paulmck@linux.vnet.ibm.com Signed-off-by: Ingo Molnar

Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net

2017-12-17T03:11:55Z

Three sets of overlapping changes, two in the packet scheduler and one in the meson-gxl PHY driver. Signed-off-by: David S. Miller

locking/core: Remove break_lock field when CONFIG_GENERIC_LOCKBREAK=y

2017-12-12T10:24:01Z

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

spinlock: Add library function to allocate spinlock buckets array

2017-12-11T14:58:39Z

Add two new library functions: alloc_bucket_spinlocks and free_bucket_spinlocks. These are used to allocate and free an array of spinlocks that are useful as locks for hash buckets. The interface specifies the maximum number of spinlocks in the array as well as a CPU multiplier to derive the number of spinlocks to allocate. The number allocated is rounded up to a power of two to make the array amenable to hash lookup. Signed-off-by: Tom Herbert Signed-off-by: David S. Miller

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

2017-11-07T09:32:44Z

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