From 9ca8dbcc65cfc63d6f5ef3312a33184e1d726e00 Mon Sep 17 00:00:00 2001 From: Yunhong Jiang Date: Tue, 4 Aug 2015 12:17:53 -0700 Subject: Add the rt linux 4.1.3-rt3 as base Import the rt linux 4.1.3-rt3 as OPNFV kvm base. It's from git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git linux-4.1.y-rt and the base is: commit 0917f823c59692d751951bf5ea699a2d1e2f26a2 Author: Sebastian Andrzej Siewior Date: Sat Jul 25 12:13:34 2015 +0200 Prepare v4.1.3-rt3 Signed-off-by: Sebastian Andrzej Siewior We lose all the git history this way and it's not good. We should apply another opnfv project repo in future. Change-Id: I87543d81c9df70d99c5001fbdf646b202c19f423 Signed-off-by: Yunhong Jiang --- kernel/lib/lockref.c | 196 +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 196 insertions(+) create mode 100644 kernel/lib/lockref.c (limited to 'kernel/lib/lockref.c') diff --git a/kernel/lib/lockref.c b/kernel/lib/lockref.c new file mode 100644 index 000000000..494994bf1 --- /dev/null +++ b/kernel/lib/lockref.c @@ -0,0 +1,196 @@ +#include +#include + +#if USE_CMPXCHG_LOCKREF + +/* + * Allow weakly-ordered memory architectures to provide barrier-less + * cmpxchg semantics for lockref updates. + */ +#ifndef cmpxchg64_relaxed +# define cmpxchg64_relaxed cmpxchg64 +#endif + +/* + * Note that the "cmpxchg()" reloads the "old" value for the + * failure case. + */ +#define CMPXCHG_LOOP(CODE, SUCCESS) do { \ + struct lockref old; \ + BUILD_BUG_ON(sizeof(old) != 8); \ + old.lock_count = READ_ONCE(lockref->lock_count); \ + while (likely(arch_spin_value_unlocked(old.lock.rlock.raw_lock))) { \ + struct lockref new = old, prev = old; \ + CODE \ + old.lock_count = cmpxchg64_relaxed(&lockref->lock_count, \ + old.lock_count, \ + new.lock_count); \ + if (likely(old.lock_count == prev.lock_count)) { \ + SUCCESS; \ + } \ + cpu_relax_lowlatency(); \ + } \ +} while (0) + +#else + +#define CMPXCHG_LOOP(CODE, SUCCESS) do { } while (0) + +#endif + +/** + * lockref_get - Increments reference count unconditionally + * @lockref: pointer to lockref structure + * + * This operation is only valid if you already hold a reference + * to the object, so you know the count cannot be zero. + */ +void lockref_get(struct lockref *lockref) +{ + CMPXCHG_LOOP( + new.count++; + , + return; + ); + + spin_lock(&lockref->lock); + lockref->count++; + spin_unlock(&lockref->lock); +} +EXPORT_SYMBOL(lockref_get); + +/** + * lockref_get_not_zero - Increments count unless the count is 0 or dead + * @lockref: pointer to lockref structure + * Return: 1 if count updated successfully or 0 if count was zero + */ +int lockref_get_not_zero(struct lockref *lockref) +{ + int retval; + + CMPXCHG_LOOP( + new.count++; + if (old.count <= 0) + return 0; + , + return 1; + ); + + spin_lock(&lockref->lock); + retval = 0; + if (lockref->count > 0) { + lockref->count++; + retval = 1; + } + spin_unlock(&lockref->lock); + return retval; +} +EXPORT_SYMBOL(lockref_get_not_zero); + +/** + * lockref_get_or_lock - Increments count unless the count is 0 or dead + * @lockref: pointer to lockref structure + * Return: 1 if count updated successfully or 0 if count was zero + * and we got the lock instead. + */ +int lockref_get_or_lock(struct lockref *lockref) +{ + CMPXCHG_LOOP( + new.count++; + if (old.count <= 0) + break; + , + return 1; + ); + + spin_lock(&lockref->lock); + if (lockref->count <= 0) + return 0; + lockref->count++; + spin_unlock(&lockref->lock); + return 1; +} +EXPORT_SYMBOL(lockref_get_or_lock); + +/** + * lockref_put_return - Decrement reference count if possible + * @lockref: pointer to lockref structure + * + * Decrement the reference count and return the new value. + * If the lockref was dead or locked, return an error. + */ +int lockref_put_return(struct lockref *lockref) +{ + CMPXCHG_LOOP( + new.count--; + if (old.count <= 0) + return -1; + , + return new.count; + ); + return -1; +} +EXPORT_SYMBOL(lockref_put_return); + +/** + * lockref_put_or_lock - decrements count unless count <= 1 before decrement + * @lockref: pointer to lockref structure + * Return: 1 if count updated successfully or 0 if count <= 1 and lock taken + */ +int lockref_put_or_lock(struct lockref *lockref) +{ + CMPXCHG_LOOP( + new.count--; + if (old.count <= 1) + break; + , + return 1; + ); + + spin_lock(&lockref->lock); + if (lockref->count <= 1) + return 0; + lockref->count--; + spin_unlock(&lockref->lock); + return 1; +} +EXPORT_SYMBOL(lockref_put_or_lock); + +/** + * lockref_mark_dead - mark lockref dead + * @lockref: pointer to lockref structure + */ +void lockref_mark_dead(struct lockref *lockref) +{ + assert_spin_locked(&lockref->lock); + lockref->count = -128; +} +EXPORT_SYMBOL(lockref_mark_dead); + +/** + * lockref_get_not_dead - Increments count unless the ref is dead + * @lockref: pointer to lockref structure + * Return: 1 if count updated successfully or 0 if lockref was dead + */ +int lockref_get_not_dead(struct lockref *lockref) +{ + int retval; + + CMPXCHG_LOOP( + new.count++; + if (old.count < 0) + return 0; + , + return 1; + ); + + spin_lock(&lockref->lock); + retval = 0; + if (lockref->count >= 0) { + lockref->count++; + retval = 1; + } + spin_unlock(&lockref->lock); + return retval; +} +EXPORT_SYMBOL(lockref_get_not_dead); -- cgit 1.2.3-korg