diff options
author | Linus Torvalds <torvalds@linux-foundation.org> | 2017-09-04 21:52:29 +0300 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2017-09-04 21:52:29 +0300 |
commit | 5f82e71a001d14824a7728ad9e49f6aea420f161 (patch) | |
tree | bf5dfa7cf0840ec834899ae925913973bd1e65d1 /Documentation/static-keys.txt | |
parent | 6c51e67b64d169419fb13318035bb442f9176612 (diff) | |
parent | edc2988c548db05e33b921fed15821010bc74895 (diff) | |
download | linux-5f82e71a001d14824a7728ad9e49f6aea420f161.tar.xz |
Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking updates from Ingo Molnar:
- Add 'cross-release' support to lockdep, which allows APIs like
completions, where it's not the 'owner' who releases the lock, to be
tracked. It's all activated automatically under
CONFIG_PROVE_LOCKING=y.
- Clean up (restructure) the x86 atomics op implementation to be more
readable, in preparation of KASAN annotations. (Dmitry Vyukov)
- Fix static keys (Paolo Bonzini)
- Add killable versions of down_read() et al (Kirill Tkhai)
- Rework and fix jump_label locking (Marc Zyngier, Paolo Bonzini)
- Rework (and fix) tlb_flush_pending() barriers (Peter Zijlstra)
- Remove smp_mb__before_spinlock() and convert its usages, introduce
smp_mb__after_spinlock() (Peter Zijlstra)
* 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (56 commits)
locking/lockdep/selftests: Fix mixed read-write ABBA tests
sched/completion: Avoid unnecessary stack allocation for COMPLETION_INITIALIZER_ONSTACK()
acpi/nfit: Fix COMPLETION_INITIALIZER_ONSTACK() abuse
locking/pvqspinlock: Relax cmpxchg's to improve performance on some architectures
smp: Avoid using two cache lines for struct call_single_data
locking/lockdep: Untangle xhlock history save/restore from task independence
locking/refcounts, x86/asm: Disable CONFIG_ARCH_HAS_REFCOUNT for the time being
futex: Remove duplicated code and fix undefined behaviour
Documentation/locking/atomic: Finish the document...
locking/lockdep: Fix workqueue crossrelease annotation
workqueue/lockdep: 'Fix' flush_work() annotation
locking/lockdep/selftests: Add mixed read-write ABBA tests
mm, locking/barriers: Clarify tlb_flush_pending() barriers
locking/lockdep: Make CONFIG_LOCKDEP_CROSSRELEASE and CONFIG_LOCKDEP_COMPLETIONS truly non-interactive
locking/lockdep: Explicitly initialize wq_barrier::done::map
locking/lockdep: Rename CONFIG_LOCKDEP_COMPLETE to CONFIG_LOCKDEP_COMPLETIONS
locking/lockdep: Reword title of LOCKDEP_CROSSRELEASE config
locking/lockdep: Make CONFIG_LOCKDEP_CROSSRELEASE part of CONFIG_PROVE_LOCKING
locking/refcounts, x86/asm: Implement fast refcount overflow protection
locking/lockdep: Fix the rollback and overwrite detection logic in crossrelease
...
Diffstat (limited to 'Documentation/static-keys.txt')
-rw-r--r-- | Documentation/static-keys.txt | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/Documentation/static-keys.txt b/Documentation/static-keys.txt index b83dfa1c0602..ab16efe0c79d 100644 --- a/Documentation/static-keys.txt +++ b/Documentation/static-keys.txt @@ -149,6 +149,26 @@ static_branch_inc(), will change the branch back to true. Likewise, if the key is initialized false, a 'static_branch_inc()', will change the branch to true. And then a 'static_branch_dec()', will again make the branch false. +The state and the reference count can be retrieved with 'static_key_enabled()' +and 'static_key_count()'. In general, if you use these functions, they +should be protected with the same mutex used around the enable/disable +or increment/decrement function. + +Note that switching branches results in some locks being taken, +particularly the CPU hotplug lock (in order to avoid races against +CPUs being brought in the kernel whilst the kernel is getting +patched). Calling the static key API from within a hotplug notifier is +thus a sure deadlock recipe. In order to still allow use of the +functionnality, the following functions are provided: + + static_key_enable_cpuslocked() + static_key_disable_cpuslocked() + static_branch_enable_cpuslocked() + static_branch_disable_cpuslocked() + +These functions are *not* general purpose, and must only be used when +you really know that you're in the above context, and no other. + Where an array of keys is required, it can be defined as:: DEFINE_STATIC_KEY_ARRAY_TRUE(keys, count); |