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| author |   Peter Zijlstra <peterz@infradead.org> | 2019-08-01 15:30:28 +0200 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2019-08-06 12:49:16 +0200 |
| commit | 24a376d65177009a4dd8d846543c5dc69f5c4ced (patch) | |
| tree | 4b228011e49f27b53e62594649dfa9e5becda37c /arch/x86/include/asm/qspinlock.h | |
| parent | locking/rwsem: Check for operations on an uninitialized rwsem (diff) | |
| download | linux-dev-24a376d65177009a4dd8d846543c5dc69f5c4ced.tar.xz linux-dev-24a376d65177009a4dd8d846543c5dc69f5c4ced.zip | |
locking/qspinlock,x86: Clarify virt_spin_lock_key
Add a few comments to clarify how this is supposed to work.
Reported-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Juergen Gross <jgross@suse.com>
Diffstat (limited to 'arch/x86/include/asm/qspinlock.h')
| -rw-r--r-- | arch/x86/include/asm/qspinlock.h | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/arch/x86/include/asm/qspinlock.h b/arch/x86/include/asm/qspinlock.h index bd5ac6cc37db..444d6fd9a6d8 100644 --- a/arch/x86/include/asm/qspinlock.h +++ b/arch/x86/include/asm/qspinlock.h @@ -63,10 +63,25 @@ static inline bool vcpu_is_preempted(long cpu) #endif #ifdef CONFIG_PARAVIRT +/* + * virt_spin_lock_key - enables (by default) the virt_spin_lock() hijack. + * + * Native (and PV wanting native due to vCPU pinning) should disable this key. + * It is done in this backwards fashion to only have a single direction change, + * which removes ordering between native_pv_spin_init() and HV setup. + */ DECLARE_STATIC_KEY_TRUE(virt_spin_lock_key); void native_pv_lock_init(void) __init; +/* + * Shortcut for the queued_spin_lock_slowpath() function that allows + * virt to hijack it. + * + * Returns: + * true - lock has been negotiated, all done; + * false - queued_spin_lock_slowpath() will do its thing. + */ #define virt_spin_lock virt_spin_lock static inline bool virt_spin_lock(struct qspinlock *lock) { |