#define arch_spin_unlock_wait(x) \
do { while (arch_spin_is_locked(x)) cpu_relax(); } while (0)
+#ifdef CONFIG_ARC_HAS_LLSC
+
+/*
+ * A normal LLOCK/SCOND based system, w/o need for livelock workaround
+ */
+#ifndef CONFIG_ARC_STAR_9000923308
+
static inline void arch_spin_lock(arch_spinlock_t *lock)
{
- unsigned int tmp = __ARCH_SPIN_LOCK_LOCKED__;
+ unsigned int val;
+
+ smp_mb();
+
+ __asm__ __volatile__(
+ "1: llock %[val], [%[slock]] \n"
+ " breq %[val], %[LOCKED], 1b \n" /* spin while LOCKED */
+ " scond %[LOCKED], [%[slock]] \n" /* acquire */
+ " bnz 1b \n"
+ " \n"
+ : [val] "=&r" (val)
+ : [slock] "r" (&(lock->slock)),
+ [LOCKED] "r" (__ARCH_SPIN_LOCK_LOCKED__)
+ : "memory", "cc");
+
+ smp_mb();
+}
+
+/* 1 - lock taken successfully */
+static inline int arch_spin_trylock(arch_spinlock_t *lock)
+{
+ unsigned int val, got_it = 0;
+
+ smp_mb();
+
+ __asm__ __volatile__(
+ "1: llock %[val], [%[slock]] \n"
+ " breq %[val], %[LOCKED], 4f \n" /* already LOCKED, just bail */
+ " scond %[LOCKED], [%[slock]] \n" /* acquire */
+ " bnz 1b \n"
+ " mov %[got_it], 1 \n"
+ "4: \n"
+ " \n"
+ : [val] "=&r" (val),
+ [got_it] "+&r" (got_it)
+ : [slock] "r" (&(lock->slock)),
+ [LOCKED] "r" (__ARCH_SPIN_LOCK_LOCKED__)
+ : "memory", "cc");
+
+ smp_mb();
+
+ return got_it;
+}
+
+static inline void arch_spin_unlock(arch_spinlock_t *lock)
+{
+ smp_mb();
+
+ lock->slock = __ARCH_SPIN_LOCK_UNLOCKED__;
+
+ smp_mb();
+}
+
+/*
+ * Read-write spinlocks, allowing multiple readers but only one writer.
+ * Unfair locking as Writers could be starved indefinitely by Reader(s)
+ */
+
+static inline void arch_read_lock(arch_rwlock_t *rw)
+{
+ unsigned int val;
+
+ smp_mb();
+
+ /*
+ * zero means writer holds the lock exclusively, deny Reader.
+ * Otherwise grant lock to first/subseq reader
+ *
+ * if (rw->counter > 0) {
+ * rw->counter--;
+ * ret = 1;
+ * }
+ */
+
+ __asm__ __volatile__(
+ "1: llock %[val], [%[rwlock]] \n"
+ " brls %[val], %[WR_LOCKED], 1b\n" /* <= 0: spin while write locked */
+ " sub %[val], %[val], 1 \n" /* reader lock */
+ " scond %[val], [%[rwlock]] \n"
+ " bnz 1b \n"
+ " \n"
+ : [val] "=&r" (val)
+ : [rwlock] "r" (&(rw->counter)),
+ [WR_LOCKED] "ir" (0)
+ : "memory", "cc");
+
+ smp_mb();
+}
+
+/* 1 - lock taken successfully */
+static inline int arch_read_trylock(arch_rwlock_t *rw)
+{
+ unsigned int val, got_it = 0;
+
+ smp_mb();
+
+ __asm__ __volatile__(
+ "1: llock %[val], [%[rwlock]] \n"
+ " brls %[val], %[WR_LOCKED], 4f\n" /* <= 0: already write locked, bail */
+ " sub %[val], %[val], 1 \n" /* counter-- */
+ " scond %[val], [%[rwlock]] \n"
+ " bnz 1b \n" /* retry if collided with someone */
+ " mov %[got_it], 1 \n"
+ " \n"
+ "4: ; --- done --- \n"
+
+ : [val] "=&r" (val),
+ [got_it] "+&r" (got_it)
+ : [rwlock] "r" (&(rw->counter)),
+ [WR_LOCKED] "ir" (0)
+ : "memory", "cc");
+
+ smp_mb();
+
+ return got_it;
+}
+
+static inline void arch_write_lock(arch_rwlock_t *rw)
+{
+ unsigned int val;
+
+ smp_mb();
+
+ /*
+ * If reader(s) hold lock (lock < __ARCH_RW_LOCK_UNLOCKED__),
+ * deny writer. Otherwise if unlocked grant to writer
+ * Hence the claim that Linux rwlocks are unfair to writers.
+ * (can be starved for an indefinite time by readers).
+ *
+ * if (rw->counter == __ARCH_RW_LOCK_UNLOCKED__) {
+ * rw->counter = 0;
+ * ret = 1;
+ * }
+ */
+
+ __asm__ __volatile__(
+ "1: llock %[val], [%[rwlock]] \n"
+ " brne %[val], %[UNLOCKED], 1b \n" /* while !UNLOCKED spin */
+ " mov %[val], %[WR_LOCKED] \n"
+ " scond %[val], [%[rwlock]] \n"
+ " bnz 1b \n"
+ " \n"
+ : [val] "=&r" (val)
+ : [rwlock] "r" (&(rw->counter)),
+ [UNLOCKED] "ir" (__ARCH_RW_LOCK_UNLOCKED__),
+ [WR_LOCKED] "ir" (0)
+ : "memory", "cc");
+
+ smp_mb();
+}
+
+/* 1 - lock taken successfully */
+static inline int arch_write_trylock(arch_rwlock_t *rw)
+{
+ unsigned int val, got_it = 0;
+
+ smp_mb();
+
+ __asm__ __volatile__(
+ "1: llock %[val], [%[rwlock]] \n"
+ " brne %[val], %[UNLOCKED], 4f \n" /* !UNLOCKED, bail */
+ " mov %[val], %[WR_LOCKED] \n"
+ " scond %[val], [%[rwlock]] \n"
+ " bnz 1b \n" /* retry if collided with someone */
+ " mov %[got_it], 1 \n"
+ " \n"
+ "4: ; --- done --- \n"
+
+ : [val] "=&r" (val),
+ [got_it] "+&r" (got_it)
+ : [rwlock] "r" (&(rw->counter)),
+ [UNLOCKED] "ir" (__ARCH_RW_LOCK_UNLOCKED__),
+ [WR_LOCKED] "ir" (0)
+ : "memory", "cc");
+
+ smp_mb();
+
+ return got_it;
+}
+
+static inline void arch_read_unlock(arch_rwlock_t *rw)
+{
+ unsigned int val;
+
+ smp_mb();
+
+ /*
+ * rw->counter++;
+ */
+ __asm__ __volatile__(
+ "1: llock %[val], [%[rwlock]] \n"
+ " add %[val], %[val], 1 \n"
+ " scond %[val], [%[rwlock]] \n"
+ " bnz 1b \n"
+ " \n"
+ : [val] "=&r" (val)
+ : [rwlock] "r" (&(rw->counter))
+ : "memory", "cc");
+
+ smp_mb();
+}
+
+static inline void arch_write_unlock(arch_rwlock_t *rw)
+{
+ smp_mb();
+
+ rw->counter = __ARCH_RW_LOCK_UNLOCKED__;
+
+ smp_mb();
+}
+
+#else /* CONFIG_ARC_STAR_9000923308 */
+
+/*
+ * HS38x4 could get into a LLOCK/SCOND livelock in case of multiple overlapping
+ * coherency transactions in the SCU. The exclusive line state keeps rotating
+ * among contenting cores leading to a never ending cycle. So break the cycle
+ * by deferring the retry of failed exclusive access (SCOND). The actual delay
+ * needed is function of number of contending cores as well as the unrelated
+ * coherency traffic from other cores. To keep the code simple, start off with
+ * small delay of 1 which would suffice most cases and in case of contention
+ * double the delay. Eventually the delay is sufficient such that the coherency
+ * pipeline is drained, thus a subsequent exclusive access would succeed.
+ */
+
+#define SCOND_FAIL_RETRY_VAR_DEF \
+ unsigned int delay, tmp; \
+
+#define SCOND_FAIL_RETRY_ASM \
+ " ; --- scond fail delay --- \n" \
+ " mov %[tmp], %[delay] \n" /* tmp = delay */ \
+ "2: brne.d %[tmp], 0, 2b \n" /* while (tmp != 0) */ \
+ " sub %[tmp], %[tmp], 1 \n" /* tmp-- */ \
+ " rol %[delay], %[delay] \n" /* delay *= 2 */ \
+ " b 1b \n" /* start over */ \
+ " \n" \
+ "4: ; --- done --- \n" \
+
+#define SCOND_FAIL_RETRY_VARS \
+ ,[delay] "=&r" (delay), [tmp] "=&r" (tmp) \
+
+static inline void arch_spin_lock(arch_spinlock_t *lock)
+{
+ unsigned int val;
+ SCOND_FAIL_RETRY_VAR_DEF;
+
+ smp_mb();
+
+ __asm__ __volatile__(
+ "0: mov %[delay], 1 \n"
+ "1: llock %[val], [%[slock]] \n"
+ " breq %[val], %[LOCKED], 0b \n" /* spin while LOCKED */
+ " scond %[LOCKED], [%[slock]] \n" /* acquire */
+ " bz 4f \n" /* done */
+ " \n"
+ SCOND_FAIL_RETRY_ASM
+
+ : [val] "=&r" (val)
+ SCOND_FAIL_RETRY_VARS
+ : [slock] "r" (&(lock->slock)),
+ [LOCKED] "r" (__ARCH_SPIN_LOCK_LOCKED__)
+ : "memory", "cc");
+
+ smp_mb();
+}
+
+/* 1 - lock taken successfully */
+static inline int arch_spin_trylock(arch_spinlock_t *lock)
+{
+ unsigned int val, got_it = 0;
+ SCOND_FAIL_RETRY_VAR_DEF;
+
+ smp_mb();
+
+ __asm__ __volatile__(
+ "0: mov %[delay], 1 \n"
+ "1: llock %[val], [%[slock]] \n"
+ " breq %[val], %[LOCKED], 4f \n" /* already LOCKED, just bail */
+ " scond %[LOCKED], [%[slock]] \n" /* acquire */
+ " bz.d 4f \n"
+ " mov.z %[got_it], 1 \n" /* got it */
+ " \n"
+ SCOND_FAIL_RETRY_ASM
+
+ : [val] "=&r" (val),
+ [got_it] "+&r" (got_it)
+ SCOND_FAIL_RETRY_VARS
+ : [slock] "r" (&(lock->slock)),
+ [LOCKED] "r" (__ARCH_SPIN_LOCK_LOCKED__)
+ : "memory", "cc");
+
+ smp_mb();
+
+ return got_it;
+}
+
+static inline void arch_spin_unlock(arch_spinlock_t *lock)
+{
+ smp_mb();
+
+ lock->slock = __ARCH_SPIN_LOCK_UNLOCKED__;
+
+ smp_mb();
+}
+
+/*
+ * Read-write spinlocks, allowing multiple readers but only one writer.
+ * Unfair locking as Writers could be starved indefinitely by Reader(s)
+ */
+
+static inline void arch_read_lock(arch_rwlock_t *rw)
+{
+ unsigned int val;
+ SCOND_FAIL_RETRY_VAR_DEF;
+
+ smp_mb();
+
+ /*
+ * zero means writer holds the lock exclusively, deny Reader.
+ * Otherwise grant lock to first/subseq reader
+ *
+ * if (rw->counter > 0) {
+ * rw->counter--;
+ * ret = 1;
+ * }
+ */
+
+ __asm__ __volatile__(
+ "0: mov %[delay], 1 \n"
+ "1: llock %[val], [%[rwlock]] \n"
+ " brls %[val], %[WR_LOCKED], 0b\n" /* <= 0: spin while write locked */
+ " sub %[val], %[val], 1 \n" /* reader lock */
+ " scond %[val], [%[rwlock]] \n"
+ " bz 4f \n" /* done */
+ " \n"
+ SCOND_FAIL_RETRY_ASM
+
+ : [val] "=&r" (val)
+ SCOND_FAIL_RETRY_VARS
+ : [rwlock] "r" (&(rw->counter)),
+ [WR_LOCKED] "ir" (0)
+ : "memory", "cc");
+
+ smp_mb();
+}
+
+/* 1 - lock taken successfully */
+static inline int arch_read_trylock(arch_rwlock_t *rw)
+{
+ unsigned int val, got_it = 0;
+ SCOND_FAIL_RETRY_VAR_DEF;
+
+ smp_mb();
+
+ __asm__ __volatile__(
+ "0: mov %[delay], 1 \n"
+ "1: llock %[val], [%[rwlock]] \n"
+ " brls %[val], %[WR_LOCKED], 4f\n" /* <= 0: already write locked, bail */
+ " sub %[val], %[val], 1 \n" /* counter-- */
+ " scond %[val], [%[rwlock]] \n"
+ " bz.d 4f \n"
+ " mov.z %[got_it], 1 \n" /* got it */
+ " \n"
+ SCOND_FAIL_RETRY_ASM
+
+ : [val] "=&r" (val),
+ [got_it] "+&r" (got_it)
+ SCOND_FAIL_RETRY_VARS
+ : [rwlock] "r" (&(rw->counter)),
+ [WR_LOCKED] "ir" (0)
+ : "memory", "cc");
+
+ smp_mb();
+
+ return got_it;
+}
+
+static inline void arch_write_lock(arch_rwlock_t *rw)
+{
+ unsigned int val;
+ SCOND_FAIL_RETRY_VAR_DEF;
+
+ smp_mb();
+
+ /*
+ * If reader(s) hold lock (lock < __ARCH_RW_LOCK_UNLOCKED__),
+ * deny writer. Otherwise if unlocked grant to writer
+ * Hence the claim that Linux rwlocks are unfair to writers.
+ * (can be starved for an indefinite time by readers).
+ *
+ * if (rw->counter == __ARCH_RW_LOCK_UNLOCKED__) {
+ * rw->counter = 0;
+ * ret = 1;
+ * }
+ */
+
+ __asm__ __volatile__(
+ "0: mov %[delay], 1 \n"
+ "1: llock %[val], [%[rwlock]] \n"
+ " brne %[val], %[UNLOCKED], 0b \n" /* while !UNLOCKED spin */
+ " mov %[val], %[WR_LOCKED] \n"
+ " scond %[val], [%[rwlock]] \n"
+ " bz 4f \n"
+ " \n"
+ SCOND_FAIL_RETRY_ASM
+
+ : [val] "=&r" (val)
+ SCOND_FAIL_RETRY_VARS
+ : [rwlock] "r" (&(rw->counter)),
+ [UNLOCKED] "ir" (__ARCH_RW_LOCK_UNLOCKED__),
+ [WR_LOCKED] "ir" (0)
+ : "memory", "cc");
+
+ smp_mb();
+}
+
+/* 1 - lock taken successfully */
+static inline int arch_write_trylock(arch_rwlock_t *rw)
+{
+ unsigned int val, got_it = 0;
+ SCOND_FAIL_RETRY_VAR_DEF;
+
+ smp_mb();
+
+ __asm__ __volatile__(
+ "0: mov %[delay], 1 \n"
+ "1: llock %[val], [%[rwlock]] \n"
+ " brne %[val], %[UNLOCKED], 4f \n" /* !UNLOCKED, bail */
+ " mov %[val], %[WR_LOCKED] \n"
+ " scond %[val], [%[rwlock]] \n"
+ " bz.d 4f \n"
+ " mov.z %[got_it], 1 \n" /* got it */
+ " \n"
+ SCOND_FAIL_RETRY_ASM
+
+ : [val] "=&r" (val),
+ [got_it] "+&r" (got_it)
+ SCOND_FAIL_RETRY_VARS
+ : [rwlock] "r" (&(rw->counter)),
+ [UNLOCKED] "ir" (__ARCH_RW_LOCK_UNLOCKED__),
+ [WR_LOCKED] "ir" (0)
+ : "memory", "cc");
+
+ smp_mb();
+
+ return got_it;
+}
+
+static inline void arch_read_unlock(arch_rwlock_t *rw)
+{
+ unsigned int val;
+
+ smp_mb();
+
+ /*
+ * rw->counter++;
+ */
+ __asm__ __volatile__(
+ "1: llock %[val], [%[rwlock]] \n"
+ " add %[val], %[val], 1 \n"
+ " scond %[val], [%[rwlock]] \n"
+ " bnz 1b \n"
+ " \n"
+ : [val] "=&r" (val)
+ : [rwlock] "r" (&(rw->counter))
+ : "memory", "cc");
+
+ smp_mb();
+}
+
+static inline void arch_write_unlock(arch_rwlock_t *rw)
+{
+ unsigned int val;
+
+ smp_mb();
+
+ /*
+ * rw->counter = __ARCH_RW_LOCK_UNLOCKED__;
+ */
+ __asm__ __volatile__(
+ "1: llock %[val], [%[rwlock]] \n"
+ " scond %[UNLOCKED], [%[rwlock]]\n"
+ " bnz 1b \n"
+ " \n"
+ : [val] "=&r" (val)
+ : [rwlock] "r" (&(rw->counter)),
+ [UNLOCKED] "r" (__ARCH_RW_LOCK_UNLOCKED__)
+ : "memory", "cc");
+
+ smp_mb();
+}
+
+#undef SCOND_FAIL_RETRY_VAR_DEF
+#undef SCOND_FAIL_RETRY_ASM
+#undef SCOND_FAIL_RETRY_VARS
+
+#endif /* CONFIG_ARC_STAR_9000923308 */
+
+#else /* !CONFIG_ARC_HAS_LLSC */
+
+static inline void arch_spin_lock(arch_spinlock_t *lock)
+{
+ unsigned int val = __ARCH_SPIN_LOCK_LOCKED__;
/*
* This smp_mb() is technically superfluous, we only need the one
__asm__ __volatile__(
"1: ex %0, [%1] \n"
" breq %0, %2, 1b \n"
- : "+&r" (tmp)
+ : "+&r" (val)
: "r"(&(lock->slock)), "ir"(__ARCH_SPIN_LOCK_LOCKED__)
: "memory");
smp_mb();
}
+/* 1 - lock taken successfully */
static inline int arch_spin_trylock(arch_spinlock_t *lock)
{
- unsigned int tmp = __ARCH_SPIN_LOCK_LOCKED__;
+ unsigned int val = __ARCH_SPIN_LOCK_LOCKED__;
smp_mb();
__asm__ __volatile__(
"1: ex %0, [%1] \n"
- : "+r" (tmp)
+ : "+r" (val)
: "r"(&(lock->slock))
: "memory");
smp_mb();
- return (tmp == __ARCH_SPIN_LOCK_UNLOCKED__);
+ return (val == __ARCH_SPIN_LOCK_UNLOCKED__);
}
static inline void arch_spin_unlock(arch_spinlock_t *lock)
{
- unsigned int tmp = __ARCH_SPIN_LOCK_UNLOCKED__;
+ unsigned int val = __ARCH_SPIN_LOCK_UNLOCKED__;
/*
* RELEASE barrier: given the instructions avail on ARCv2, full barrier
__asm__ __volatile__(
" ex %0, [%1] \n"
- : "+r" (tmp)
+ : "+r" (val)
: "r"(&(lock->slock))
: "memory");
/*
* Read-write spinlocks, allowing multiple readers but only one writer.
+ * Unfair locking as Writers could be starved indefinitely by Reader(s)
*
* The spinlock itself is contained in @counter and access to it is
* serialized with @lock_mutex.
- *
- * Unfair locking as Writers could be starved indefinitely by Reader(s)
*/
-/* Would read_trylock() succeed? */
-#define arch_read_can_lock(x) ((x)->counter > 0)
-
-/* Would write_trylock() succeed? */
-#define arch_write_can_lock(x) ((x)->counter == __ARCH_RW_LOCK_UNLOCKED__)
-
/* 1 - lock taken successfully */
static inline int arch_read_trylock(arch_rwlock_t *rw)
{
arch_spin_unlock(&(rw->lock_mutex));
}
+#endif
+
+#define arch_read_can_lock(x) ((x)->counter > 0)
+#define arch_write_can_lock(x) ((x)->counter == __ARCH_RW_LOCK_UNLOCKED__)
+
#define arch_read_lock_flags(lock, flags) arch_read_lock(lock)
#define arch_write_lock_flags(lock, flags) arch_write_lock(lock)
Code Review / kvmfornfv.git / blobdiff