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-rw-r--r--arch/powerpc/lib/locks.c65
1 files changed, 65 insertions, 0 deletions
diff --git a/arch/powerpc/lib/locks.c b/arch/powerpc/lib/locks.c
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+++ b/arch/powerpc/lib/locks.c
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+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Spin and read/write lock operations.
+ *
+ * Copyright (C) 2001-2004 Paul Mackerras <paulus@au.ibm.com>, IBM
+ * Copyright (C) 2001 Anton Blanchard <anton@au.ibm.com>, IBM
+ * Copyright (C) 2002 Dave Engebretsen <engebret@us.ibm.com>, IBM
+ * Rework to support virtual processors
+ */
+
+#include <linux/kernel.h>
+#include <linux/spinlock.h>
+#include <linux/export.h>
+#include <linux/smp.h>
+
+/* waiting for a spinlock... */
+#if defined(CONFIG_PPC_SPLPAR)
+#include <asm/hvcall.h>
+#include <asm/smp.h>
+
+void splpar_spin_yield(arch_spinlock_t *lock)
+{
+ unsigned int lock_value, holder_cpu, yield_count;
+
+ lock_value = lock->slock;
+ if (lock_value == 0)
+ return;
+ holder_cpu = lock_value & 0xffff;
+ BUG_ON(holder_cpu >= NR_CPUS);
+
+ yield_count = yield_count_of(holder_cpu);
+ if ((yield_count & 1) == 0)
+ return; /* virtual cpu is currently running */
+ rmb();
+ if (lock->slock != lock_value)
+ return; /* something has changed */
+ yield_to_preempted(holder_cpu, yield_count);
+}
+EXPORT_SYMBOL_GPL(splpar_spin_yield);
+
+/*
+ * Waiting for a read lock or a write lock on a rwlock...
+ * This turns out to be the same for read and write locks, since
+ * we only know the holder if it is write-locked.
+ */
+void splpar_rw_yield(arch_rwlock_t *rw)
+{
+ int lock_value;
+ unsigned int holder_cpu, yield_count;
+
+ lock_value = rw->lock;
+ if (lock_value >= 0)
+ return; /* no write lock at present */
+ holder_cpu = lock_value & 0xffff;
+ BUG_ON(holder_cpu >= NR_CPUS);
+
+ yield_count = yield_count_of(holder_cpu);
+ if ((yield_count & 1) == 0)
+ return; /* virtual cpu is currently running */
+ rmb();
+ if (rw->lock != lock_value)
+ return; /* something has changed */
+ yield_to_preempted(holder_cpu, yield_count);
+}
+#endif