Merge branch 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking fixes from Ingo Molnar: "Misc fixes: lockstat fix, futex fix on !MMU systems, big endian fix for qrwlocks and a race fix for pvqspinlocks" * 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: locking/pvqspinlock: Fix a bug in qstat_read() locking/pvqspinlock: Fix double hash race locking/qrwlock: Fix write unlock bug on big endian systems futex: Assume all mappings are private on !MMU systems
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commit
1f8083c640
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@ -25,7 +25,20 @@
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#include <asm-generic/qrwlock_types.h>
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/*
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* Writer states & reader shift and bias
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* Writer states & reader shift and bias.
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*
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* | +0 | +1 | +2 | +3 |
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* ----+----+----+----+----+
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* LE | 78 | 56 | 34 | 12 | 0x12345678
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* ----+----+----+----+----+
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* | wr | rd |
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* +----+----+----+----+
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*
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* ----+----+----+----+----+
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* BE | 12 | 34 | 56 | 78 | 0x12345678
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* ----+----+----+----+----+
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* | rd | wr |
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* +----+----+----+----+
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*/
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#define _QW_WAITING 1 /* A writer is waiting */
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#define _QW_LOCKED 0xff /* A writer holds the lock */
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@ -133,13 +146,23 @@ static inline void queued_read_unlock(struct qrwlock *lock)
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(void)atomic_sub_return_release(_QR_BIAS, &lock->cnts);
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}
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/**
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* __qrwlock_write_byte - retrieve the write byte address of a queue rwlock
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* @lock : Pointer to queue rwlock structure
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* Return: the write byte address of a queue rwlock
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*/
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static inline u8 *__qrwlock_write_byte(struct qrwlock *lock)
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{
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return (u8 *)lock + 3 * IS_BUILTIN(CONFIG_CPU_BIG_ENDIAN);
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}
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/**
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* queued_write_unlock - release write lock of a queue rwlock
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* @lock : Pointer to queue rwlock structure
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*/
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static inline void queued_write_unlock(struct qrwlock *lock)
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{
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smp_store_release((u8 *)&lock->cnts, 0);
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smp_store_release(__qrwlock_write_byte(lock), 0);
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}
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/*
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@ -179,7 +179,15 @@ int __read_mostly futex_cmpxchg_enabled;
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* Futex flags used to encode options to functions and preserve them across
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* restarts.
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*/
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#ifdef CONFIG_MMU
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# define FLAGS_SHARED 0x01
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#else
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/*
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* NOMMU does not have per process address space. Let the compiler optimize
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* code away.
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*/
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# define FLAGS_SHARED 0x00
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#endif
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#define FLAGS_CLOCKRT 0x02
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#define FLAGS_HAS_TIMEOUT 0x04
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@ -405,6 +413,16 @@ static void get_futex_key_refs(union futex_key *key)
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if (!key->both.ptr)
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return;
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/*
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* On MMU less systems futexes are always "private" as there is no per
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* process address space. We need the smp wmb nevertheless - yes,
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* arch/blackfin has MMU less SMP ...
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*/
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if (!IS_ENABLED(CONFIG_MMU)) {
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smp_mb(); /* explicit smp_mb(); (B) */
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return;
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}
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switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) {
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case FUT_OFF_INODE:
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ihold(key->shared.inode); /* implies smp_mb(); (B) */
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@ -436,6 +454,9 @@ static void drop_futex_key_refs(union futex_key *key)
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return;
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}
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if (!IS_ENABLED(CONFIG_MMU))
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return;
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switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) {
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case FUT_OFF_INODE:
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iput(key->shared.inode);
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@ -450,7 +450,7 @@ pv_wait_head_or_lock(struct qspinlock *lock, struct mcs_spinlock *node)
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goto gotlock;
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}
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}
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WRITE_ONCE(pn->state, vcpu_halted);
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WRITE_ONCE(pn->state, vcpu_hashed);
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qstat_inc(qstat_pv_wait_head, true);
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qstat_inc(qstat_pv_wait_again, waitcnt);
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pv_wait(&l->locked, _Q_SLOW_VAL);
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@ -153,7 +153,6 @@ static ssize_t qstat_read(struct file *file, char __user *user_buf,
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*/
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if ((counter == qstat_pv_latency_kick) ||
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(counter == qstat_pv_latency_wake)) {
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stat = 0;
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if (kicks)
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stat = DIV_ROUND_CLOSEST_ULL(stat, kicks);
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}
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