Hello Thomas,
I have build an implementation for the routine
futex_atomic_cmpxchg_inatomic() to make PTHREAD_PRIO_INHERIT mutex
work on ARM.
Compared to other architectures where CPU specific assembler is used,
it is probably not the most optimal implementation possible, but I
tested it successfully on a Atmel AT91RM9200 core, and it could work
on other (UP) architectures as well.
What do you think of it?
Or do you know a better solution?
Kind Regards,
Remy
Index: linux-2.6.21/include/asm/futex.h
===================================================================
--- linux-2.6.21.orig/include/asm/futex.h 2007-04-26 05:08:32.000000000 +0200
+++ linux-2.6.21/include/asm/futex.h 2007-07-06 15:11:01.000000000 +0200
@@ -1,6 +1,79 @@
-#ifndef _ASM_FUTEX_H
-#define _ASM_FUTEX_H
+#ifndef _ASM_ARM_FUTEX_H
+#define _ASM_ARM_FUTEX_H
-#include <asm-generic/futex.h>
+#ifdef __KERNEL__
+
+#include <linux/futex.h>
+#include <asm/errno.h>
+#include <asm/uaccess.h>
+
+static inline int
+futex_atomic_op_inuser (int encoded_op, int __user *uaddr)
+{
+ int op = (encoded_op >> 28) & 7;
+ int cmp = (encoded_op >> 24) & 15;
+ int oparg = (encoded_op << 8) >> 20;
+ int cmparg = (encoded_op << 20) >> 20;
+ int oldval = 0, ret;
+ if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
+ oparg = 1 << oparg;
+
+ if (! access_ok (VERIFY_WRITE, uaddr, sizeof(int)))
+ return -EFAULT;
+
+ pagefault_disable();
+
+ switch (op) {
+ case FUTEX_OP_SET:
+ case FUTEX_OP_ADD:
+ case FUTEX_OP_OR:
+ case FUTEX_OP_ANDN:
+ case FUTEX_OP_XOR:
+ default:
+ ret = -ENOSYS;
+ }
+
+ pagefault_enable();
+
+ if (!ret) {
+ switch (cmp) {
+ case FUTEX_OP_CMP_EQ: ret = (oldval == cmparg); break;
+ case FUTEX_OP_CMP_NE: ret = (oldval != cmparg); break;
+ case FUTEX_OP_CMP_LT: ret = (oldval < cmparg); break;
+ case FUTEX_OP_CMP_GE: ret = (oldval >= cmparg); break;
+ case FUTEX_OP_CMP_LE: ret = (oldval <= cmparg); break;
+ case FUTEX_OP_CMP_GT: ret = (oldval > cmparg); break;
+ default: ret = -ENOSYS;
+ }
+ }
+ return ret;
+}
+
+static inline int
+futex_atomic_cmpxchg_inatomic(int __user *uaddr, int oldval, int newval)
+{
+ int err = 0;
+ int uval;
+ unsigned long flags;
+
+ if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int)))
+ return -EFAULT;
+
+ local_irq_save(flags);
+
+ err = get_user(uval, uaddr);
+ if (err)
+ {
+ local_irq_restore(flags);
+ return -EFAULT;
+ }
+ if (uval == oldval)
+ err = put_user(newval, uaddr);
+
+ local_irq_restore(flags);
+
+ if (err) return -EFAULT;
+ return uval;
+}
#endif
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