Merge branch 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking fixes from Ingo Molnar: "Two fixes: the paravirt spin_unlock() corruption/crash fix, and an rtmutex NULL dereference crash fix" * 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: x86/spinlocks/paravirt: Fix memory corruption on unlock locking/rtmutex: Avoid a NULL pointer dereference on deadlock
This commit is contained in:
commit
10436cf881
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@ -46,7 +46,7 @@ static __always_inline bool static_key_false(struct static_key *key);
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static inline void __ticket_enter_slowpath(arch_spinlock_t *lock)
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{
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set_bit(0, (volatile unsigned long *)&lock->tickets.tail);
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set_bit(0, (volatile unsigned long *)&lock->tickets.head);
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}
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#else /* !CONFIG_PARAVIRT_SPINLOCKS */
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@ -60,10 +60,30 @@ static inline void __ticket_unlock_kick(arch_spinlock_t *lock,
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}
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#endif /* CONFIG_PARAVIRT_SPINLOCKS */
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static inline int __tickets_equal(__ticket_t one, __ticket_t two)
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{
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return !((one ^ two) & ~TICKET_SLOWPATH_FLAG);
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}
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static inline void __ticket_check_and_clear_slowpath(arch_spinlock_t *lock,
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__ticket_t head)
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{
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if (head & TICKET_SLOWPATH_FLAG) {
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arch_spinlock_t old, new;
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old.tickets.head = head;
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new.tickets.head = head & ~TICKET_SLOWPATH_FLAG;
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old.tickets.tail = new.tickets.head + TICKET_LOCK_INC;
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new.tickets.tail = old.tickets.tail;
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/* try to clear slowpath flag when there are no contenders */
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cmpxchg(&lock->head_tail, old.head_tail, new.head_tail);
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}
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}
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static __always_inline int arch_spin_value_unlocked(arch_spinlock_t lock)
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{
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return lock.tickets.head == lock.tickets.tail;
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return __tickets_equal(lock.tickets.head, lock.tickets.tail);
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}
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/*
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@ -87,18 +107,21 @@ static __always_inline void arch_spin_lock(arch_spinlock_t *lock)
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if (likely(inc.head == inc.tail))
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goto out;
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inc.tail &= ~TICKET_SLOWPATH_FLAG;
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for (;;) {
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unsigned count = SPIN_THRESHOLD;
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do {
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if (READ_ONCE(lock->tickets.head) == inc.tail)
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goto out;
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inc.head = READ_ONCE(lock->tickets.head);
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if (__tickets_equal(inc.head, inc.tail))
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goto clear_slowpath;
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cpu_relax();
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} while (--count);
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__ticket_lock_spinning(lock, inc.tail);
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}
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out: barrier(); /* make sure nothing creeps before the lock is taken */
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clear_slowpath:
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__ticket_check_and_clear_slowpath(lock, inc.head);
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out:
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barrier(); /* make sure nothing creeps before the lock is taken */
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}
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static __always_inline int arch_spin_trylock(arch_spinlock_t *lock)
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@ -106,56 +129,30 @@ static __always_inline int arch_spin_trylock(arch_spinlock_t *lock)
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arch_spinlock_t old, new;
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old.tickets = READ_ONCE(lock->tickets);
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if (old.tickets.head != (old.tickets.tail & ~TICKET_SLOWPATH_FLAG))
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if (!__tickets_equal(old.tickets.head, old.tickets.tail))
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return 0;
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new.head_tail = old.head_tail + (TICKET_LOCK_INC << TICKET_SHIFT);
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new.head_tail &= ~TICKET_SLOWPATH_FLAG;
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/* cmpxchg is a full barrier, so nothing can move before it */
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return cmpxchg(&lock->head_tail, old.head_tail, new.head_tail) == old.head_tail;
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}
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static inline void __ticket_unlock_slowpath(arch_spinlock_t *lock,
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arch_spinlock_t old)
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{
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arch_spinlock_t new;
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BUILD_BUG_ON(((__ticket_t)NR_CPUS) != NR_CPUS);
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/* Perform the unlock on the "before" copy */
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old.tickets.head += TICKET_LOCK_INC;
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/* Clear the slowpath flag */
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new.head_tail = old.head_tail & ~(TICKET_SLOWPATH_FLAG << TICKET_SHIFT);
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/*
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* If the lock is uncontended, clear the flag - use cmpxchg in
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* case it changes behind our back though.
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*/
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if (new.tickets.head != new.tickets.tail ||
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cmpxchg(&lock->head_tail, old.head_tail,
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new.head_tail) != old.head_tail) {
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/*
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* Lock still has someone queued for it, so wake up an
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* appropriate waiter.
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*/
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__ticket_unlock_kick(lock, old.tickets.head);
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}
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}
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static __always_inline void arch_spin_unlock(arch_spinlock_t *lock)
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{
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if (TICKET_SLOWPATH_FLAG &&
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static_key_false(¶virt_ticketlocks_enabled)) {
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arch_spinlock_t prev;
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static_key_false(¶virt_ticketlocks_enabled)) {
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__ticket_t head;
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prev = *lock;
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add_smp(&lock->tickets.head, TICKET_LOCK_INC);
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BUILD_BUG_ON(((__ticket_t)NR_CPUS) != NR_CPUS);
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/* add_smp() is a full mb() */
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head = xadd(&lock->tickets.head, TICKET_LOCK_INC);
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if (unlikely(lock->tickets.tail & TICKET_SLOWPATH_FLAG))
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__ticket_unlock_slowpath(lock, prev);
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if (unlikely(head & TICKET_SLOWPATH_FLAG)) {
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head &= ~TICKET_SLOWPATH_FLAG;
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__ticket_unlock_kick(lock, (head + TICKET_LOCK_INC));
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}
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} else
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__add(&lock->tickets.head, TICKET_LOCK_INC, UNLOCK_LOCK_PREFIX);
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}
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@ -164,14 +161,15 @@ static inline int arch_spin_is_locked(arch_spinlock_t *lock)
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{
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struct __raw_tickets tmp = READ_ONCE(lock->tickets);
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return tmp.tail != tmp.head;
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return !__tickets_equal(tmp.tail, tmp.head);
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}
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static inline int arch_spin_is_contended(arch_spinlock_t *lock)
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{
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struct __raw_tickets tmp = READ_ONCE(lock->tickets);
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return (__ticket_t)(tmp.tail - tmp.head) > TICKET_LOCK_INC;
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tmp.head &= ~TICKET_SLOWPATH_FLAG;
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return (tmp.tail - tmp.head) > TICKET_LOCK_INC;
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}
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#define arch_spin_is_contended arch_spin_is_contended
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@ -191,8 +189,8 @@ static inline void arch_spin_unlock_wait(arch_spinlock_t *lock)
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* We need to check "unlocked" in a loop, tmp.head == head
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* can be false positive because of overflow.
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*/
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if (tmp.head == (tmp.tail & ~TICKET_SLOWPATH_FLAG) ||
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tmp.head != head)
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if (__tickets_equal(tmp.head, tmp.tail) ||
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!__tickets_equal(tmp.head, head))
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break;
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cpu_relax();
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@ -609,7 +609,7 @@ static inline void check_zero(void)
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u8 ret;
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u8 old;
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old = ACCESS_ONCE(zero_stats);
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old = READ_ONCE(zero_stats);
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if (unlikely(old)) {
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ret = cmpxchg(&zero_stats, old, 0);
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/* This ensures only one fellow resets the stat */
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@ -727,6 +727,7 @@ __visible void kvm_lock_spinning(struct arch_spinlock *lock, __ticket_t want)
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int cpu;
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u64 start;
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unsigned long flags;
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__ticket_t head;
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if (in_nmi())
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return;
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@ -768,11 +769,15 @@ __visible void kvm_lock_spinning(struct arch_spinlock *lock, __ticket_t want)
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*/
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__ticket_enter_slowpath(lock);
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/* make sure enter_slowpath, which is atomic does not cross the read */
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smp_mb__after_atomic();
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/*
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* check again make sure it didn't become free while
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* we weren't looking.
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*/
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if (ACCESS_ONCE(lock->tickets.head) == want) {
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head = READ_ONCE(lock->tickets.head);
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if (__tickets_equal(head, want)) {
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add_stats(TAKEN_SLOW_PICKUP, 1);
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goto out;
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}
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@ -803,8 +808,8 @@ static void kvm_unlock_kick(struct arch_spinlock *lock, __ticket_t ticket)
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add_stats(RELEASED_SLOW, 1);
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for_each_cpu(cpu, &waiting_cpus) {
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const struct kvm_lock_waiting *w = &per_cpu(klock_waiting, cpu);
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if (ACCESS_ONCE(w->lock) == lock &&
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ACCESS_ONCE(w->want) == ticket) {
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if (READ_ONCE(w->lock) == lock &&
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READ_ONCE(w->want) == ticket) {
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add_stats(RELEASED_SLOW_KICKED, 1);
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kvm_kick_cpu(cpu);
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break;
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@ -41,7 +41,7 @@ static u8 zero_stats;
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static inline void check_zero(void)
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{
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u8 ret;
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u8 old = ACCESS_ONCE(zero_stats);
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u8 old = READ_ONCE(zero_stats);
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if (unlikely(old)) {
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ret = cmpxchg(&zero_stats, old, 0);
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/* This ensures only one fellow resets the stat */
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@ -112,6 +112,7 @@ __visible void xen_lock_spinning(struct arch_spinlock *lock, __ticket_t want)
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struct xen_lock_waiting *w = this_cpu_ptr(&lock_waiting);
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int cpu = smp_processor_id();
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u64 start;
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__ticket_t head;
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unsigned long flags;
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/* If kicker interrupts not initialized yet, just spin */
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*/
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__ticket_enter_slowpath(lock);
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/* make sure enter_slowpath, which is atomic does not cross the read */
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smp_mb__after_atomic();
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/*
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* check again make sure it didn't become free while
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* we weren't looking
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*/
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if (ACCESS_ONCE(lock->tickets.head) == want) {
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head = READ_ONCE(lock->tickets.head);
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if (__tickets_equal(head, want)) {
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add_stats(TAKEN_SLOW_PICKUP, 1);
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goto out;
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}
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const struct xen_lock_waiting *w = &per_cpu(lock_waiting, cpu);
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/* Make sure we read lock before want */
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if (ACCESS_ONCE(w->lock) == lock &&
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ACCESS_ONCE(w->want) == next) {
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if (READ_ONCE(w->lock) == lock &&
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READ_ONCE(w->want) == next) {
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add_stats(RELEASED_SLOW_KICKED, 1);
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xen_send_IPI_one(cpu, XEN_SPIN_UNLOCK_VECTOR);
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break;
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@ -1193,7 +1193,8 @@ rt_mutex_slowlock(struct rt_mutex *lock, int state,
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ret = __rt_mutex_slowlock(lock, state, timeout, &waiter);
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if (unlikely(ret)) {
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remove_waiter(lock, &waiter);
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if (rt_mutex_has_waiters(lock))
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remove_waiter(lock, &waiter);
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rt_mutex_handle_deadlock(ret, chwalk, &waiter);
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}
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