patch-2.3.49 linux/include/linux/brlock.h

• Lines: 208
• Date: Thu Mar 2 14:01:19 2000
• Orig file: v2.3.48/linux/include/linux/brlock.h
• Orig date: Wed Dec 31 16:00:00 1969

diff -u --recursive --new-file v2.3.48/linux/include/linux/brlock.h linux/include/linux/brlock.h
@@ -0,0 +1,207 @@
+#ifndef __LINUX_BRLOCK_H
+#define __LINUX_BRLOCK_H
+
+/*
+ * 'Big Reader' read-write spinlocks.
+ *
+ * super-fast read/write locks, with write-side penalty. The point
+ * is to have a per-CPU read/write lock. Readers lock their CPU-local
+ * readlock, writers must lock all locks to get write access. These
+ * CPU-read-write locks are semantically identical to normal rwlocks.
+ * Memory usage is higher as well. (NR_CPUS*L1_CACHE_BYTES bytes)
+ *
+ * The most important feature is that these spinlocks do not cause
+ * cacheline ping-pong in the 'most readonly data' case.
+ *
+ * Copyright 2000, Ingo Molnar <mingo@redhat.com>
+ *
+ * Registry idea and naming [ crutial! :-) ] by:
+ *
+ *                 David S. Miller <davem@redhat.com>
+ *
+ * David has an implementation that doesnt use atomic operations in
+ * the read branch via memory ordering tricks - i guess we need to
+ * split this up into a per-arch thing? The atomicity issue is a
+ * secondary item in profiles, at least on x86 platforms.
+ *
+ * The atomic op version overhead is indeed a big deal on
+ * load-locked/store-conditional cpus (ALPHA/MIPS/PPC) and
+ * compare-and-swap cpus (Sparc64).  So we control which
+ * implementation to use with a __BRLOCK_USE_ATOMICS define. -DaveM
+ */
+
+/* Register bigreader lock indices here. */
+enum brlock_indices {
+	BR_GLOBALIRQ_LOCK,
+	BR_NETPROTO_LOCK,
+
+	__BR_END
+};
+
+#include <linux/config.h>
+
+#ifdef CONFIG_SMP
+
+#include <linux/cache.h>
+#include <linux/spinlock.h>
+
+#if defined(__i386__)
+#define __BRLOCK_USE_ATOMICS
+#else
+#undef __BRLOCK_USE_ATOMICS
+#endif
+
+#ifdef __BRLOCK_USE_ATOMICS
+typedef rwlock_t	brlock_read_lock_t;
+#else
+typedef unsigned int	brlock_read_lock_t;
+#endif
+
+/*
+ * align last allocated index to the next cacheline:
+ */
+#define __BR_IDX_MAX \
+	(((sizeof(brlock_read_lock_t)*__BR_END + SMP_CACHE_BYTES-1) & ~(SMP_CACHE_BYTES-1)) / sizeof(brlock_read_lock_t))
+
+extern brlock_read_lock_t __brlock_array[NR_CPUS][__BR_IDX_MAX];
+
+#ifndef __BRLOCK_USE_ATOMICS
+struct br_wrlock {
+	spinlock_t lock;
+} __attribute__ ((__aligned__(SMP_CACHE_BYTES)));
+
+extern struct br_wrlock __br_write_locks[__BR_IDX_MAX];
+#endif
+
+extern void __br_lock_usage_bug (void);
+
+#ifdef __BRLOCK_USE_ATOMICS
+
+extern inline void br_read_lock (enum brlock_indices idx)
+{
+	/*
+	 * This causes a link-time bug message if an
+	 * invalid index is used:
+	 */
+	if (idx >= __BR_END)
+		__br_lock_usage_bug();
+
+	read_lock(&__brlock_array[smp_processor_id()][idx]);
+}
+
+extern inline void br_read_unlock (enum brlock_indices idx)
+{
+	if (idx >= __BR_END)
+		__br_lock_usage_bug();
+
+	read_unlock(&__brlock_array[smp_processor_id()][idx]);
+}
+
+#else /* ! __BRLOCK_USE_ATOMICS */
+extern inline void br_read_lock (enum brlock_indices idx)
+{
+	unsigned int *ctr;
+	spinlock_t *lock;
+
+	/*
+	 * This causes a link-time bug message if an
+	 * invalid index is used:
+	 */
+	if (idx >= __BR_END)
+		__br_lock_usage_bug();
+
+	ctr = &__brlock_array[smp_processor_id()][idx];
+	lock = &__br_write_locks[idx].lock;
+again:
+	(*ctr)++;
+	rmb();
+	if (spin_is_locked(lock)) {
+		(*ctr)--;
+		rmb();
+		while (spin_is_locked(lock))
+			barrier();
+		goto again;
+	}
+}
+
+extern inline void br_read_unlock (enum brlock_indices idx)
+{
+	unsigned int *ctr;
+
+	if (idx >= __BR_END)
+		__br_lock_usage_bug();
+
+	ctr = &__brlock_array[smp_processor_id()][idx];
+
+	wmb();
+	(*ctr)--;
+}
+#endif /* __BRLOCK_USE_ATOMICS */
+
+/* write path not inlined - it's rare and larger */
+
+extern void FASTCALL(__br_write_lock (enum brlock_indices idx));
+extern void FASTCALL(__br_write_unlock (enum brlock_indices idx));
+
+extern inline void br_write_lock (enum brlock_indices idx)
+{
+	if (idx >= __BR_END)
+		__br_lock_usage_bug();
+	__br_write_lock(idx);
+}
+
+extern inline void br_write_unlock (enum brlock_indices idx)
+{
+	if (idx >= __BR_END)
+		__br_lock_usage_bug();
+	__br_write_unlock(idx);
+}
+
+#else
+# define br_read_lock(idx)	((void)(idx))
+# define br_read_unlock(idx)	((void)(idx))
+# define br_write_lock(idx)	((void)(idx))
+# define br_write_unlock(idx)	((void)(idx))
+#endif
+
+/*
+ * Now enumerate all of the possible sw/hw IRQ protected
+ * versions of the interfaces.
+ */
+#define br_read_lock_irqsave(idx, flags) \
+	do { local_irq_save(flags); br_read_lock(idx); } while (0)
+
+#define br_read_lock_irq(idx) \
+	do { local_irq_disable(); br_read_lock(idx); } while (0)
+
+#define br_read_lock_bh(idx) \
+	do { local_bh_disable(); br_read_lock(idx); } while (0)
+
+#define br_write_lock_irqsave(idx, flags) \
+	do { local_irq_save(flags); br_write_lock(idx); } while (0)
+
+#define br_write_lock_irq(idx) \
+	do { local_irq_disable(); br_write_lock(idx); } while (0)
+
+#define br_write_lock_bh(idx) \
+	do { local_bh_disable(); br_write_lock(idx); } while (0)
+
+#define br_read_unlock_irqrestore(idx, flags) \
+	do { br_read_unlock(irx); local_irq_restore(flags); } while (0)
+
+#define br_read_unlock_irq(idx) \
+	do { br_read_unlock(idx); local_irq_enable(); } while (0)
+
+#define br_read_unlock_bh(idx) \
+	do { br_read_unlock(idx); local_bh_enable(); } while (0)
+
+#define br_write_unlock_irqrestore(idx, flags) \
+	do { br_write_unlock(irx); local_irq_restore(flags); } while (0)
+
+#define br_write_unlock_irq(idx) \
+	do { br_write_unlock(idx); local_irq_enable(); } while (0)
+
+#define br_write_unlock_bh(idx) \
+	do { br_write_unlock(idx); local_bh_enable(); } while (0)
+
+#endif /* __LINUX_BRLOCK_H */